Air Con compressor magnetic clutch not engaging!

[Silver Surfer]

Guys,

I have not had the luxury of air con for the last 4 months....it's a killer in this weather.
I initially thought it was due to leak of the gas as I had topped it up several times with no-lasting effect.
after looking into it further...it turns out that there is plenty of refrigerant gas and pressure is holding....the problem was that the AC compressor was not engaging when AC is switched on with the car running!!

There is no power to the magnetic clutch of the AC compressor...
On direct power to it..it works so no fault there.

The AC relay under the front bonnet works on applying power to it.
The 10A fuse in the engine bay is intact.

I even swapped the AC head unit from my working Red car to the non-working White car and still no effect in activating it when AC is switched on.
The AC head unit swapped in from White car to Red car also works on the Red car.....and prove the head units from each car is OK.

What next?

Please advice.

Thanks

SS

[duncan]

So Head unit OK, motor and clutch OK, fuse OK, relay OK, just leaves the trinary electrical switch and the wires between everything.
As a first pass you’re half way through the elimation process, just keep going.
Using a multimeter or car bulb on a flying lead.
Switching side of relay
With demand on, I.e head unit set to minimum,
is their power to (the switching side) of the relay and separately a good earth.
Power side of relay,
power to fuse, power to relay, power to compressor, try to establish if continuity exists.
If all those are OK then would say check the trinary switch and it’s wires.
Good luck, with no A/C the cabin is not the best place to be.

[Kaz-kzukNA1]

As duncan suggested, you are halfway through there.... Keep trying.

Sharing my experience as well.


Question for you.
Did the R & L condenser fans switch on when you requested the a/c on?
The compressor may not engage but both condenser fans should.



13512

13513

Carry out Self Diag first.

Might as well do the Function & Operation check.

Follow the above procedure in the pdf files.


If evaporator sensor is disconnected, it will use fail safe value of -1degC and this will prevent the CL from engaging.
Evapo sensor has to see above +4degC to keep engaging the CL in order to prevent itself from freezing.


https://lh3.googleusercontent.com/EZomGeFgOpwa3AwjemP_9wfo--EU0oxA4P_LTvIBs_5YkcjAhzAJKbIa9dSmWZJwJMAB77vhnOkN 53eZR1XO52ivqdWzXg22kheg6pWOdFJpBEivtqBuwhIwt0wVxZ 9HDoO6rek3jls-G2JdZnZWEpQmk_LgleX4sylq8d9sLebGkzRUJwbEaj4nV8Ai8S 3w_rRWEDD62cvpduGUHSJUJ8ja0RbmBnUPvTmyTPjGVR-wmm09WIob74TTVOQOsrBXzhJCkaKAx6WZyvhFRj3UEJDjIK1r7 BASPWgNn2f44rTJGzh8LrQe06DAHzrjtZnm83d3hekvLdc6YzG M6_iw7MRBaAIf1OOc30dOj7IB4RX3rji_IvwvGewIjmc2ANxIv X16J5t6V3D7lWzdyQB_vu6xdeLALeuDqZbO9WItqX-YQUdCJ1cLRxUFqjBO-GJLSlzKkKT2ikpy10TcsSxYv-vrebibm68fmh_T9oLGszak_inieuZDtTjhmx3IrqlI1phNDIg0-ESiAimSqIVtixRRMDTv7pjzOMNTiR5u9QFNBhN_flMVS1joLDH 15-4eCWJgs6NtctF1J3rjpvaOy8hy8If8bXMHtc__NOVx=w1080-h608-no
If someone worked inside the cabin, the sensor connector could be left unplugged.

This is the heater unit under/behind the dashboard.

The blower motor housing sits at the left side of this photo.

The connector is located at the passenger side, behind the vertical carpet or side of the glove box, the one marked in blue in the above photo.




http://www.nsxcb.co.uk/entry.php?2050-Eng-Refresh-LMA-etc-55

Also, double check the connector at the tripple pressure switch described in the above link.

On several NSX, I saw it being partially disconnected and not fully locked.
This will also prevent the CL from engaging.


There is also a chance of Fan Cotnrol Unit failure with hair line soldering cracks but normally, it will fail in the other way round - all fans (condensor, rad, even the eng bay one) engages even when eng is still cold and before even starting the eng so for now, I'll leave this one.

Good luck.


Kaz

[Silver Surfer]

Well...the mystery continues to boggle me...

The seems to be no power to the magnetic clutch of the compressor...there is also no power to the relay which switches on and off perfectly normally with clicking sound heard on switching on AC on and off. The relay works also tested off the car!

I had sent a wire from the relay directly to the compressor to ensure continuity.....and still no effect!

I have bridged the Tripple switch and it makes no difference.
I have checked fuse number 4 in the passenger footwell and there is power and the fuse is intact.
I have checked the ambient temp sensor at the front of the car ... and that is intact and working as it should.

I have checked the cabin temperature sensor and the resistance was high!..>4k ohms....should be around 1-2K ohms (N.B. the colder the cabin..the higher the resistance) ...so I thought the cabin temp sensor thinks it is ice cold so inhibiting the AC compressor..so I bypass this with a 1.5K resistor..even change the sensor from my red car ...still no effect!!

I am really at a loss here!

I have not checked the evaporator ...I will do that now.

SS

[NSXGB]

Have you run the diagnostics?

[Hagasan]

I'm only just very quickly reading the thread and replying. Doesn't the a/c have a rev limit cut-out to protect the compressor over pressuring the system? Could there be a stray signal inhibiting the running of the system? Maybe since your turbo install something was changed? It's a bit of a guess but as Simon say's (and you should alway do what Simon Say's ��) have you run the self diagnostics on the ccu?

[goldnsx]

Not sure what the ECU does. Someone in the past claimed (this and much more...) there was a switch below the pedal which tells the ECU to shut off the A/C. I've never found such a switch. From my experience with my old A/C comp it kicked it even at 7000 rpm which ate away the A/C clutch (with the new one I shut the A/C while driving madly).

[Mark N]

I'm only just very quickly reading the thread and replying. Doesn't the a/c have a rev limit cut-out to protect the compressor over pressuring the system? Could there be a stray signal inhibiting the running of the system? Maybe since your turbo install something was changed? It's a bit of a guess but as Simon say's (and you should alway do what Simon Say's ��) have you run the self diagnostics on the ccu?

Hi Hagasan
How would someone find and test the Rev limiter cut out on the a/c ? The reason I ask I have had two compressors brake (destroy themselves) both times when I have been moving let’s say quickly and was wondering if this could be the reason . The first one I put down to age. The second which was only a few months old and was an upgraded one from America I had no idea why that seized. Any information or ideas greatly received.

Regards
Mark

[goldnsx]

By 'upgraded' compressor do you mean 'rebuilt'? The rebuilt one are prone to fail. The other reason could be that the flushing was not throughly enough. Or the oil level was too low.

[Silver Surfer]

Air con self check mode :

A?C On

Open Positional Signal Circuit for mode control motor or mode door stuck?

13518

Not pressed

13519

Pressed

SS

[Silver Surfer]

Would this stop the A/C Compressor clutch from engaging??

The Function Selection and Operational Check is all OK...All 8 steps are sequencing with all the display as shown on the PDF Manual.

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13520

SS

[Silver Surfer]

Kaz,

Do I still need to check the Evaporator sensor ?
If I do...where exactly is it?
Is it under where passenger feet directly? is it above the toes? Is it to the right side towards the centre console?

Thanks

SS

[NSXGB]

Kaz,

Do I still need to check the Evaporator sensor ?
If I do...where exactly is it?
Is it under where passenger feet directly? is it above the toes? Is it to the right side towards the centre console?

Thanks

SS

"The connector is located at the passenger side, behind the vertical carpet or side of the glove box, the one marked in blue in the above photo."

[Silver Surfer]

"The connector is located at the passenger side, behind the vertical carpet or side of the glove box, the one marked in blue in the above photo."

3 vertical carpets
Glovebox has 2 sides.

My guess it will be the outer side of Right foot towards centre console....


SS

[Mark N]

By 'upgraded' compressor do you mean 'rebuilt'? The rebuilt one are prone to fail. The other reason could be that the flushing was not throughly enough. Or the oil level was too low.

No it was not rebuilt. When I say upgraded i believe it was slightly bigger that the OEM one. Honda uk wanted silly money for a replacement .Someone recommended buying it from America I think the company was Rock autos from what I can remember. It had a slightly bigger pulley from what I recall . I remember I had all sorts of problems trying to get a replacement belt because it was slightly longer. Eventually I found one so I bought two it was made by Gates part number gates 4pk948
I replaced the tension pulley at the same time . I also had the system degased cleaned and re-presurized .We also fitted a new dryer and all was working perfect for months. Then one day after a spirited drive I parked up . The next day turned car and A/C on and it squilled it had seized just as I was going out for a nsx meeting. I had to cut the belt to stop it driving. Not used A/C since. The oil level was measured out and all was done by qualified auto A/C engineer who had been in the business for years.

I wondered if a bit of debris was still in system until I saw this blog hence my enquiry.

Mark

[NSXGB]

Only one vertical carpet in mine' to the side of the centre console. See the photo above, you can see the metal pipes that go through the front firewall, that should help you picture the orientation better?

[Mark N]

By 'upgraded' compressor do you mean 'rebuilt'? The rebuilt one are prone to fail. The other reason could be that the flushing was not throughly enough. Or the oil level was too low.

No it was not rebuilt. When I say upgraded i believe it was slightly bigger that the OEM one. Honda uk wanted silly money for a replacement .Someone recommended buying it from America I think the company was Rock autos from what I can remember. It had a slightly bigger pulley from what I recall . I remember I had all sorts of problems trying to get a replacement belt because it was slightly longer. Eventually I found one so I bought two it was made by Gates part number gates 4pk948
I replaced the tension pulley at the same time . I also had the system degased cleaned and re-presurized .We also fitted a new dryer and all was working perfect for months. Then one day after a spirited drive I parked up . The next day turned car and A/C on and it squilled it had seized just as I was going out for a nsx meeting. I had to cut the belt to stop it driving. Not used A/C since. The oil level was measured out and all was done by qualified auto A/C engineer who had been in the business for years.

I wondered if a bit of debris was still in system until I saw this blog hence my enquiry.

Mark

[Silver Surfer]

Main issue, is that there is no power to the compressor..what is the reason/

SS

[Hagasan]

Hi Hagasan
How would someone find and test the Rev limiter cut out on the a/c ? The reason I ask I have had two compressors brake (destroy themselves) both times when I have been moving let’s say quickly and was wondering if this could be the reason . The first one I put down to age. The second which was only a few months old and was an upgraded one from America I had no idea why that seized. Any information or ideas greatly received.

Regards
Mark

Hi Mark,

I'm not sure as I was only really thinking out loud. I was just wondering if there could be some kind of safety cut-out from the ECU to the CCU that disables the compressor power in high rev conditions to protect it?

Gary

[Hagasan]

Main issue, is that there is no power to the compressor..what is the reason/

SS

Kare, this is what I was trying to determine. Could there be a power cut-off signal sent from CCU to disengage the clutch? If there is on these cars then could something be causing that rogue signal to kill the power to yours? I don't know if there is such a safety cut-out though. I'm assuming it's earthed ok? Not the compressor body but the clutch as I think you said you sent power direct to it? I seem to remember from another make of car that there was a shorter earth jumpered across from the clutch assembly onto the compressor body to earth it. Is that on the NSX? I'm at work so can't physically look at anything...

[Silver Surfer]

My mechanic has tested all links to the compressor from the Relay with his high tech volt/resistance meter under the front bonnet..there is no bad earth detected.

SS

[Silver Surfer]

When 12V is applied to the socket next to the Dipstick...the Magnetic clutch engages with A/C on.
So something somewhere is preventing power to the relay...!

13521

SS

[Kaz-kzukNA1]

SS, back to my original post #3.

Does both R&L condenser fans switch On when you request the A/C On?

While you have 'Mode' motor issue, that won't prevent comp. CL from engaging.

The Self Diag test shows that your Evapo temperature sensor is at least properly connected.
Never heard of this sensor failing so very unlikely to be the cause but still, a possibility.

Just to be clear, your Function and Operation check failed for Mode 1 - 5 unless the comp. CL engaged.
I believe it didn’t engage.
During this test, all sensors except the evapo temperature are ignored for the comp. CL control.

There is no rpm based limiter for the comp. on our NSX.
That's why there is an aftermarket circuit board for this.

If you press A/C switch to manually request A/C On, press Defrost SW or set temperature dial to 18degC, the system bypasses the cabin/outside temperature control and goes straight to evapo temperature control mode only.

Fan Control Unit (FCU) uses Rad fan temperature sensor, CCU A/C request signal, Triple Press SW A(Hi/Lo) and decides whether to tell ECU that it can engage the comp. CL or not.

ECU is the one that controls the comp. CL relay (ACC terminal) with the input from FCU.
It goes to low level when engaging the comp. CL.
It uses Triple Pess SW B (mid) for idle rpm compensation.


So, somewhere in this loop, you have a problem and first thing first, please check my question above.
Also, you could have wiring issue somewhere in the above loop so this may mean nothing but since it's easy to do, you may want swapping the FCU with the known good one.
Obviously, if wiring issue, this won't change anything.



Kaz

[Silver Surfer]

Thanks Kaz

will check as you have instructed.

thanks muchly

SS

[Silver Surfer]

I have now carried further testing.

When the A/C is switched on...both condenser fan is working.

I have swapped the FCU from the other car...it has not sorted out the problem...still no power to the Compressor clutch.

frustrating!

SS

[goldnsx]

Are you low on freon? You write that you have enough pressure in the system but how do you know? The only way to be sure is to evacuate and refill...

From your earlier posts (#4) maybe your stator on the compressor is bad. If you give 12V to the compressor wire does it run then?

[Silver Surfer]

The system has been pressure tested with nitrogen at 100psi.. after 24hrs ..rechecked and pressure remained at 100psi.. so no leak. Then the system was vacuumed and fresh ‘freon’was placed ..800ml with oil lubricants and confirmed filled to capacity.
By applying 12v to the compressor plug by the oil dipstick.. the compressor runs and engages the magnetic clutch .
Running a wire from the relay to the compressor plus gave no joy as there was no power to the relay to send to the compressor. The relay clicks on and off on pressing the A/C button and Off button. So the relay works. I even swap the relay for ones next to it... still no joy.
My deduction is there may be a break from the CCU to the relay??

SS

[goldnsx]

Yes and no, I guess you're on the track. I've been looking a little bit deeping into the chematics ...

According to page 22-10 in the SM: you've tried another relay with no success. If it's clicking whenever you switch on the A/C (with engine running of course) the CCU must be sending a signal and the ECU sends this signal to ground. Otherwise it would not be clicking. But you still get no power to the A/C clutch. You're assuming that the relay stays open when you hear it clicking BUT is this really the case?
A little bit 'embarassing' test: but did you check fuse no. 21 (10 A)? Fuse no. 9 (120 A) 'must' be working because the whole car would not run without it.

With A/C ON you should have voltage at the YEL/BLK wire. That's my theory because you hear the relay clicking, so the CCU is sending a signal (still unsure if if stays open). Now, if the fuse checked out OK you should check the voltage/resistance PNK/ORN and RED wires.

My first test would be the fuse, then the wire from the relay to the plug near the oil dipstick and lastly the wire from the relay to the 120 A fuse.

After re-reading the whole thread your mechanic all checked out. The solution seems to be so easy to your problem that I'm asking myself if he really checked the right wires/components...

BTW and OT but we talked about it in this thread. On page 22-15: Pin 13 of the 14P is for the 'engine revolution pulse'. Maybe the CCU decides on the engine rpms to shut off the A/C. Just a guess.

[Silver Surfer]

As a temporary measure to bail me out for the trip to Spa this weekend in this 30 degree Celsius... would it be safe for me to power the A/C compressor with a self made switch to the power supply?


SS

[goldnsx]

I guess you would have to switch it ON and OFF every minute or so. With 30 deg C outside maybe less frequently. But you can't monitor the pressure. Pretty unsure if the compressor decides to blow up.

[Kaz-kzukNA1]

So, both condenser fans operated when the a/c is switched On.
That the information I wanted.

CCU is sending the a/c On request to the FCU.
FCU has received the request and checked the Triple Pres A status as well as the Rad fan temperature sensor.
If happy with the result, send the comp. CL On request to the ECU and at the same time, activate the R&L condenser fans.
So, one side of the loop is operating properly and closed apart from Triple Press SW A status.
There could be a state where the condenser fans were activated but because the pressure was too low or too high, the compressor can't be engaged.
However, you already tried bypassing the Triple Press A.....

Now the other side.

ECU is the one that activates/deactivates the comp. CL relay and this is where the problem is.

In your latest post, you mentioned that this relay clicks when pressing the manual override A/C switch On and Off at the CCU.
This is a new info for us.
This means that the coil side of the relay is working and thus, ECU is actually activating/deactivating the comp. CL relay based on the request from the FCU.

So, in theory, both loops are functioning properly and thus, the logic level has no problem.

This leaves us with the switch side of the comp.CL relay so more of wiring or relay, fuse, etc parts issue.

Presuming that you were looking at the correct relay for the comp.CL and the fact that swapping it with another relay didn't make any difference, then chances are, you don't have the high side power source at the relay connector.
It is through the #21 10A fuse inside the eng bay where you can find the jump start terminal and in your earlier post, you already mentioned that this fuse is fine.
It's the PNK/ORN wire running from the eng bay fuse box to the stuck of multiple connectors located at the forward left side of the cabin behind the glove box so not an easy task to check.

I'm bit busy with the potential crank pulley weight issue on another NSX but will take a simple photo and show further test method.

In the meantime, as goldnsx mentioned, please first confirm whether you have permanent +B voltage or not (regardless of IGSW status) at the PNK/ORG wire terminal at the comp.CL relay socket.
If no power, then whatever the cause, that is the reason for not engaging the comp.CL.
If you have confirmed that you don't have the permanent +B at the PNK/ORG wire, de-pin it and create 10A fused single wire from the pentagonal/octagonal relay box under the bonnet with 250 terminal at the other end so that you can swap it in place of the original PNK/ORG wire?
This will be the safest method as you will keep all the logic control.


Kaz

[britlude]

So to recap.... The clutch engages if you power it directly.... The AC relay can be controlled by the CCU.... So need to establish where the voltage is lost....

Is there the 12v at the relay, that the relay switches to make the clutch engage... Remove the relay, check the supply is there..... Try shorting the 12v supply to the clutch wire, ie..Pretend you are the relay.... Does it engage? Check a fuse hasn't blown after this.... put a test lead on the output side of the relay holder and check the relay is outputting the 12v when the CCU is asking it to..... If all that is ok, check the continuity between the relay holder and clutch wire....

My gearbox issue was the connectors behind the driver's seat (2 blue, 2 grey) that connect the floor loom and the engine loom, not got my manual handy, but these are subject to vibration and caused a signal to be lost....

...so have to check if there's any other connectors in the clutch feed circuit....

[Silver Surfer]

12 V direct to A/C clutch works.
All fuses intact
Relay switches ok on activating A/C.
Condensor fans work on switching on A/C.
FCU intact (checked on other car).
ACU intact (checked on other car)
NO Power from fuse (rear ) and hence no power to Relay coil to A/C compressor...just no power to its coil on +ve side feed.
Continuity from fuse in back to Relay..Good
Continuity from Relay to Compressor ...Good

SS

[NSXGB]

....just take the Red car :)

[Kaz-kzukNA1]

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Very good point, NSXGB.


So, to confirm that we are talking about the same thing, this is what you have.

The relay position.
This could be different depending on the spec of your NSX but I presume you are talking about the early model one so should be the same.
Please ignore the shape/colour of the surrounding other relays inside the box.
They are different depending on the country/year model/etc spec.






https://lh3.googleusercontent.com/BC_dV6Fglzz0EBuk_I5ckGfv0Nty7PYX-UuJ_NZ46N1wLdKCPD5-YQL4WDtfGeoBxE8BUO9pNj-6RIHfbypIm1oecWCr6oo2b025pkYawuj6bkbCOkcSFXGt7wBRp 9t9AmuCQ7WJaiWNdCTjSm6mpu_wdPq5MOoH3JBDAe8p4imGraL 7gt-r7myvCwHNOnFFNGPvhngZBSMsYhEZeV2RnjOeYR6Cmsk2mrmE-lsEYSz6U-g9Up-1yXTJSZ8vrliaWS2bqzCy9UC_KoM85qjO0Wfs5vOI-5iwKvFaEQuj9hhDOMelf80lzBEom2FnLSmLILDfvBar9sMVEuP ss4rtXdWM7HvJIbgM0dF-0-xFjPKzp2QwrWE-k0mEdFFE7EQr1Tkw16emSd7QSDXCCrlHlN34EVChcrLwpV43-YPyIaxyO6Ga1cXf_m-IInVgdJPngyHYijbry4f5OcRR4pDiJlYi-QbCYA3B7E_HMCqf-gQaNmTL1Vqrq7iAiUFdEqL2bfv79CwRgPH2rD1TfHH7nntv9aE QcOJqV1aMA9TC8s1_hl8_q1f7EwYXhcSicDLgKch9rSGAG1GHc GR2hQpAbY9GiwRkiPA6hIxTXp5W=w1080-h608-no
The simplified circuit diagram.

I believe you don't have permanent +B at #3.

For your reference;
#1. IG2
At +Ve only when IGSW in P2 ON.

#2. ECU ACC
ECU a/c CL control.
Please use only the digital multimeter to be on the safe side if using ohm range. Safer if DC voltage range used.
FCU CL Off request to ECU: Floating voltage but would be close to 0.00V. Open circuit, infinite resistance.
FCU CL On request to ECU: Steady low voltage close to GND level, about 0.03V. About 100ohm or steady resistance.

#3. +B
Permanent +B battery voltage regardless of IGSW status.
You seem to have lost this for some reason.

#4. comp.CL
A/C compressor CL, wire goes all the way back to the eng bay to the 1pin connector next to the oil level dip stick.







https://lh3.googleusercontent.com/N6mN4MKGNj-tqwRtYABHrIVs43iS2RmTUMWYSty7C2atb__RvII-Vq8utOnsUYry2XdrQYV9J8HeODpSCUMMB47F5X6IEa1UGkCjFA pPGXa4xWC0KOVxt_czlNzP4pTZJkbSVHgFaEJ-lQwU1PQ7m6noUnPkxCimx6zH28dd7KobddGK5X0951ciL7Q8hK E-pnPvIKV9esqsFtq_L2BM4No6izuYZpYOHGQC1SIuQaTCheWK_b zvlP1SBNX--CuAFotdFDSJclPl0v0DTs3ObzAh-lCs3Fv6zqseeYjpffgRt-y-MsQINSdzVNoiw6cso7jJvE0aI0-q8aPBt69_7ZshOt1aINLUNw3Y2K0gCdR7C0XTQKpdx5QTKQy3z dnoSgnwtwKSMj1ReezT5Cu1nDSJ8NeRvq0N_eJLIdhzL-kUYmMa8kNnLxCcAvDY3pVnVYxejA6dZGFTn4btz-SLGQM1UsOcamJ5LqSLy5P2TaW6pYwNyP9ur4vnnTfGr5qVeKXs TbCgg2wgfSnojCCntaTIniujN_qa7_QgT_KwOGJ909WuqDnF0k 7_ED12deOW7Q00eFlUbAmpJ8os_p7qdft6VboJj-cGVIlV8vyx=w1080-h608-no
If you have #3. +B, this will engage the CL whenever you turn the SW in the above photo On even without running the eng..










https://lh3.googleusercontent.com/5dZ7iQIVbbMTiwP2oksrSmOuOYNQP9QaTyJSniKYwNXCt8xD6Q a1B29Oj9rdJ3z66DdXAfHVa2LB1COY8y9xH7yrEMAGuhPNXZM_ l5jpAlUxlijQYEtqA5AEiNp1CH06OLqPSGWN5o_cOZf14P5y6N sBH3S9zZICth2YiGn3H3NSELjEmNsSceK4chCwERsED6A8BqpY XjQg9VSS7xwmCI7CZR35AHb7GkyKs_Fhlbd_oo0UgJgYz9Mmp3 6vXu71bPuMRWU_FmQbDeEfL7LuCzzL0_Q-KvL3URKSLNrsCIGLIWRxFxqkUnIOdjgTgNg2sNEwr-d83A1yTq5xMY9WspqeToProJkh2lTr5L5tTK3NcGbaZ27vdov5 xSy9cCvcER4ForSj2pRoo1SfU3zaXu9FlZaKhqSN2If6zMv3vE NdTQWzINZeIZC0eLfsXcDIJSszoHeVcPa8-L2vPX4-S0_bYS45p8WyAOE6l11_DWw8C4O93qdycR-SA7LvjImYMzypVaV8aEPqd5vsoN4uMSSv0rmvFcaEet7aE-GDU3h1nNN4lESRH2nIVhggzcgzgxKFI18d3dR2skNk5gZgWXHG Pu9BCVwCvtE1utsq=w1080-h608-no
If you have the time, you can trace where the +B disappears from the fuse box inside the eng bay through the Side wire harness running L side of the cabin to the multiple connector stack behind the glove box.
Then via Front wire harness, it reaches the relay box under the bonnet.

For a temporary fix, if you don't have +B at #3, you could just create single wire with 10A fuse as close as possible to the pentagonal relay box and swap in the 250 terminal into the relay socket.



I hope it's something very simple.....



[Update: just saw your latest post.

12 V direct to A/C clutch works.
All fuses intact
....................
Continuity from fuse in back to Relay..Good
Continuity from Relay to Compressor ...Good

SS
If this is true, your wiring from the fuse box to relay box #3 terminal should be good.

https://lh3.googleusercontent.com/uBELWEPylNG83SF0Cvo-iKs_QjsOXy10wv-3O3bofKialgk0kvchGDBoEBSfDYkT_XHYRyNkV1rHlVkfpPSDg X2GVZm6fwoI9Fl8SUkH-fpnn3-WT5_skE6VAal-TY7r2Fk9CggHNOImBTgOS6R7X8Nasi-j8s8UjIP1Oy49KG0QBUvz8QFQ8Y22DtCVH6tM4e5SPTLKKcYRM GNSlOrrfPsQtiOHqQqVZBx4ozYMvXGuo7glwkCoP_oJPDmeGm7 ZeDnUPijy5HmpPOu2koILkI7nUJKolQ1ERvtF9L8rgHxnKTTZN xuHDdt_eQ_e7ZiMsivoMAMxMRBGTOhyAT7PY-uCO8sHjqPA2qV0swpgwqUhR3e9YBuqzTyTsYeqTYQausgshTwA 6bSsezFlDZ8x5mMQ96cKzZbYT7A1ROX4kIfg_kD5V5iBu8zm9x 622OAnQhf5Cg9j9faF-8muNnD0uwL_yjd6WEIzn5YOb8WW2mc0hHK-vYMkAl47mqrShJ30A77R_UPO1wSTQkCU7YP3hCIHBDNDGL7FSs JPgYVuNJ9N4qlKe8Ic3kHnN4-WgwaUonXAMPZSqUEvuhDhYpKKd5rqsnJBlZYpR-Qb-iUl=w1080-h608-no
What is the voltage reading at the #21 10A fuse inside the eng bay?
You must apply the probe to the blue side while keeping the fuse in place. This is the fused side, after the fuse.
Yellow is the source side and before the fuse.

If you have battery power at blue side after the fuse, there is something not checked properly.]




Kaz

[goldnsx]

https://lh3.googleusercontent.com/uBELWEPylNG83SF0Cvo-iKs_QjsOXy10wv-3O3bofKialgk0kvchGDBoEBSfDYkT_XHYRyNkV1rHlVkfpPSDg X2GVZm6fwoI9Fl8SUkH-fpnn3-WT5_skE6VAal-TY7r2Fk9CggHNOImBTgOS6R7X8Nasi-j8s8UjIP1Oy49KG0QBUvz8QFQ8Y22DtCVH6tM4e5SPTLKKcYRM GNSlOrrfPsQtiOHqQqVZBx4ozYMvXGuo7glwkCoP_oJPDmeGm7 ZeDnUPijy5HmpPOu2koILkI7nUJKolQ1ERvtF9L8rgHxnKTTZN xuHDdt_eQ_e7ZiMsivoMAMxMRBGTOhyAT7PY-uCO8sHjqPA2qV0swpgwqUhR3e9YBuqzTyTsYeqTYQausgshTwA 6bSsezFlDZ8x5mMQ96cKzZbYT7A1ROX4kIfg_kD5V5iBu8zm9x 622OAnQhf5Cg9j9faF-8muNnD0uwL_yjd6WEIzn5YOb8WW2mc0hHK-vYMkAl47mqrShJ30A77R_UPO1wSTQkCU7YP3hCIHBDNDGL7FSs JPgYVuNJ9N4qlKe8Ic3kHnN4-WgwaUonXAMPZSqUEvuhDhYpKKd5rqsnJBlZYpR-Qb-iUl=w1080-h608-no

If you have battery power at blue side after the fuse, there is something not checked properly.]

Kaz

This is a little bit confusing. If you take the fuse out you should read +B on one and 0V on the other. Measured with one probe tip on the fuse and the other one against G (chassis or engine block).

If you leave the fuse in place you should read the same voltage (+B). The fuse has no resistance.

[Kaz-kzukNA1]

That's the whole point.
One think that the fuse is fine but it could be not.

By the way, automotive (or any) fuse has resistance and this is why each car manufactures have their own spec for temperature increase figure for each fuse capacity with terminal material in mind.
Usually, the resistance is in the order of milliohm but still, the fuse will get hot as the current flows and if they are placed inside the eng room, etc where it could get really hot, you need to select the fuse spec and terminal material carefully or design the fuse box position to meet the fuse spec otherwise the fuse terminal may melt or it can't meet the specified rated current flow. In Japan, automotive fuse is specified under JASO spec.

Kaz

[goldnsx]

That the way they are designed. Yes, they have a minimal resistance in the range of milliohms. But with no load attatched you'll read approx. the same voltage (within +-0.1). Even with high-current you won't see a drop like 0.2 V or so because it would melt. I don't know exactly how much Watt it takes to blow it. But with 10 A current draw, a resulting 0.2V drop would mean 2 W of heat at the little fuse. Standard resistors can cope 0.25 W, so you could imagine the voltage drop (also the resistance) must be lower to not blow a fuse. Ergo you won't see voltage drops of several Volts over a standard automotive fuse.

[Silver Surfer]

Sorry guys

My apology for further confusion.
it turns out that the issue is that there is no power to the coil of the relay to switch it on... although I can hear clicking on pressing the A/C button.

SS

[goldnsx]

Sorry for my comment but unless you're a giraffe which would use its feet to press the A/C button and be able to hear/monitor the relay the clicking you hear doesn't tell that much. :D

Do you have +B at pin no. 3 in the picture Kaz showed??? Yes or No.

[Silver Surfer]

Yes..there is power at pin +B .... but no power to Relay coil.

Again.. sorry for confusion.

SS

[Silver Surfer]

Clicking noice on pressing A\C comes from behind ?? FCU activating.. not Relay which I initially thought.
Relay definitely intact.

only temp option is bypass the Relay with a switchable connection run into the cabin and manually turn the compressor on and off every few mins😞

SS

[Kaz-kzukNA1]

Probably you are busy with the preparation so please get back to us when you can.

Not sure which relay you were hearing at the back.

The condenser fan relay is sitting almost next to the com.CL one in the same relay box under the bonnet so you may heard that one although the sound of R/L condenser fans are very loud.....



As people uses the wording 'power' in different way and to prevent confusion, please check the following.

1. Go back to my post #35.

Q1: Is your comp.CL relay located at the same position as mine?

2. Remove relay.

Q2. What is the voltage at [#1. IG2] when IGSW in P2 ON position?
Should be about 12V.

3. For Q3, use digital multimeter and not the analogue one.
If don't have one and using the analogue meter, use DC voltage range and not the ohm range.

Q3. Set IGSW into P2 ON.
If you don't have digital multimeter, jump to Q4.
With your digital multimeter, what is the resistance between the GND (battery power GND is nearby) and the [#2. ECU ACC] when pressing the [A/C] override switch at the CCU display On and Off?
Should be open circuit when Off.
Should be steady resistance when On.
If not, ECU is not allowing the comp.CL to engage.
Skip Q4 and Jump to 4.

Q4. If using analogue multimeter, set it in DC voltage range.
You will be measuring less than 0.1V but start with high enough range.
Set IGSW into P2 ON.
What is the voltage at the [#2. ECU ACC] against the GND (battery power GND is nearby) when pressing the [A/C] override switch at the CCU display On and Off?
Will be floating or close to 0.001 - 0.01V when Off.
Will be steady low voltage like 0.03V when On.
If not, ECU is not allowing the comp.CL to engage.

4. Switch off IGSW.

5. You already confirmed that you have battery voltage at the [#3. +B].

Q5. If you short [#3. +B] and [#4: comp.CL] terminals like in my photo, does the CL engage at the compressor?
No need to start the engine.
You will see the clearance of about 0.5mm goes to zero.


Kaz

[Silver Surfer]

Q5 answer:
by jumping the +B terminal like your pic... the A/C compressor engages and permanently on.

SS

[Silver Surfer]

Q2 answer
12v

[Silver Surfer]

Have now rigged up manual switch from relay socket to run in cabin for me to control manually .
Just like Kaz’s photo:

13523

SS

[Silver Surfer]

My emergency toggle switch for aircon
13524
on

13525
Off

functional!

SS

[Heineken]

A nice workaround, even with illumination :D
Still curious what the real problem might be ..

[Kaz-kzukNA1]

Saw a photo of you with bonnet opened while in the long queue for the Eurotunnel.
Possibly, activating the switch.
As long as you didn't overcharge the refrigerant, you won't hit the triple pressure switch max threshold and just needs preventing the evaporator from being frozen.

On your return, you will need to check the voltage at ECU terminal ACS and ACC.


Kaz

[Silver Surfer]

Quick update..

This was now beginning to be beyond my expertise...so asked my friendly neighborhood Auto electrician to have a look...
I dismantled the centre console for him exposing the A/C ECU and gave him the manual.

After 2.5 hours..he said he has fixed the problem.
He said the issue was :
There was no wire outfrom my New standalone ECU for the Turbo install to the main harness. He found another output that operated negative when the A/C is switched on and re-wired with diodes to protect that circuit. This energises the clutch relay.

Really happy!!

SS

[Heineken]

Thank you very much for the update!