Heating

[paulc]

Wonderful, cold weather arrives and my nsx's heating packs up. Anybody any ideas?? Is this my CCU giving up the ghost, the car warms up as normal. If it is the CCU what is the best way to remove it?? Its a NA1 JDM model.

Many thanks

Paul

[NSXGB]

This is a good place to start: http://www.nsxprime.com/FAQ/DIY/climate_control.htm

[Kaz-kzukNA1]

Hi, Paul.
Could you provide us with bit more information?
What to you mean by ‘heating packed up’?

Are you experiencing;
fan control only operates at max speed,
nothing on the CCU display,
only cold air comes out of the vent,
can’t change the vent mode or something else?

Depending on your answer, it could be the CCU issue, air in the heater core, water valve linkage or something else.

Kaz

[Sudesh]

Wonderful, cold weather arrives and my nsx's heating packs up. Anybody any ideas?? Is this my CCU giving up the ghost, the car warms up as normal. If it is the CCU what is the best way to remove it?? Its a NA1 JDM model.

Many thanks

Paul

Sound like your saying you have no hot air coming into the cabin?

[paulc]

Hi Sudesh none whats so ever, very cold last weekend!!

[goldnsx]

Have a look on the mechanical side first. Does the water valve under the 'bonnet' react if you select hot or cold? Make sure the water valve operates.

[paulc]

Many thanks will have a go this weekend.

Many regards

Paul

[paulc]

Hi gold nsx, my mechanical knowledge is not that great, not sure what you mean by the water value under the bonnet.

Regards

Paul

[NSXGB]

Have a look on the mechanical side first. Does the water valve under the 'bonnet' react if you select hot or cold? Make sure the water valve operates.

This should operate when you run the diagnostic test from the Prime link above. From the info provided so far, that would have been my guess as the culprit.

[paulc]

Many thanks have down loaded the ifo from the Prime Link and will give it a go this weekend, see what happens

Regards

Paul

[Kaz-kzukNA1]

Hi, Paul.

Photos and text in the following post may help you as well.
Please note that this information is for the RHD model so good for your NSX.

http://www.nsxcb.co.uk/showthread.php?5940-CCU-Computer-board-Service-Part-1-3&p=54812#post54812 (http://www.nsxcb.co.uk/showthread.php?5940-CCU-Computer-board-Service-Part-1-3&p=54812#post54812)


In the first photo, you can see silver aluminium pipe.
This is the heater coolant return pipe.
When you set your CCU at 32degC with the engine fully warmed up, please briefly touch it.
Please be careful as it could be very hot.

If it is not hot or just mild, then your water valve is not moving or you have lots of air inside the heater core.
The 2nd and 3rd photos in the above link show where the water valve should be at 32degC as well as at 18degC setup.

From time to time, if someone worked in the front compartment under the bonnet, the cable linkage (the top centre green arrow in the 1st photo) was not placed back in its original position and thus, the water valve won't move even the cable was moving.
On several occasions, I saw the other end of the cable linkage inside the cabin was dislocated when someone worked behind the centre console or dashboard resulting in the same issue.

CCU failure will also prevent the water valve control but this failure mode is not that common.

If the heater core has lots of air, you can bleed it by opening the bleeder plug or cap fairly easily.


At this stage, the cause of your issue is not clear so I thought about not going any further but since lots of NSX is running with some amount of air in the heater core without being noticed, other owners may find the following info useful.


Followings are based on the assumption that you don't have other cooling system issues and the air was trapped in the heater core because it was not bled properly/thoroughly last time.

On our NSX, this is where most of the air is trapped unless you have other issues on your cooling system and once the air is trapped in the heater core section, it is not easy to push it out back to the header tank by the standard coolant flow.

Depending on the year model, you will have the bleeder plug or cap at the silver aluminium heater coolant return pipe.
The 1st photo in the above link shows the bleeder plug as my NSX is 94 JDM.
If your NSX is earlier model, it will be a rubber cap instead.

If you have rubber cap as the bleeder, you can follow the procedures in the next paragraph.
If you have bleeder plug like mine, you must first confirm whether your plug is seized or not by applying small torque.
Otherwise, you may cause bigger issue.
The bleeder plug is torqued only at 9.8Nm but if the coolant was not serviced properly or if the air was left inside the heater core for many years (i.e., air behind the bleeder plug instead of coolant), the oxidation/corrosion will seize the thread at the bleeder plug.
Please remember that you are dealing with narrow/thin aluminium pipe and applying huge torque will kink the pipe or in the worst case scenario, you will create crack and leakage. Best to replace it as it is not expensive (at least in Japan, it's sided so not compatible with the one on LHD).
I have seen so many NSX with seized bleeder plug on this return pipe so it is now my standard procedure to keep at least one spare at my place.


To bleed the air from heater core, let the engine to cool down completely.
Set the CCU to 32degC with IG in On position (lots of lights on the dash) but do not start the engine.
Wait for about 10sec to let the water valve to move and then switch off the IG and remove the key.
Slowly remove the coolant header tank cap in the engine bay and make sure you have coolant close to MAX level.
Open the bleeder but very-very-very slowly. Arm yourself with lots of paper towel below and above the pipe because if you have air in the heater core, it will shoot out as a bubble and splash it. If you have rubber cap bleeder, it may shoot out in sideway as well.
Once you get the steady steram of coolant, close the bleeder. For bleeder plug, it's 9.8Nm and for rubber cap, put the hose clamp back in place.
Top up the coolant with the same one in your system and close the tank cap.


Even I use vacuum fill process after servicing the cooling system on NSX, I always follow the above procedure before and after carrying out the test driving session to make sure I don't leave even a tiny amount of air in the system.


Hope you can find the cause of your issue over the weekend.

Kaz

[goldnsx]

Thanks for the info, Kaz.

I don't know if it's just me but I think the heating capabilities of the NSX are inferior to other cars. I don't know if it's the mid-engine layout but I have to adjust to 28 degrees C or so to get it warm and cosy and this is with the A/C OFF. WITH A/C ON it feels even colder. I was thinking about trapped air but I was very cautious when filling it up. Before I'll check it again, I'd like to know what other experienced. In the US they recommend having the nose of the car down when filling.

[NSXGB]

I don't think I have ever set my temp to more than 22˚C, more than hot enough for me.


Thanks for the info, Kaz.

I don't know if it's just me but I think the heating capabilities of the NSX are inferior to other cars. I don't know if it's the mid-engine layout but I have to adjust to 28 degrees C or so to get it warm and cosy and this is with the A/C OFF. WITH A/C ON it feels even colder. I was thinking about trapped air but I was very cautious when filling it up. Before I'll check it again, I'd like to know what other experienced. In the US they recommend having the nose of the car down when filling.

[paulc]

Kaz many thanks for this, I will get cracking this weekend and let you know the outcome.

Many regards

Paul

[Sudesh]

Good to see another JDM car on the site too!

Id love to get a record going of how many are in the UK/Ireland.

[scottg]

Thanks for the info, Kaz.

I don't know if it's just me but I think the heating capabilities of the NSX are inferior to other cars. I don't know if it's the mid-engine layout but I have to adjust to 28 degrees C or so to get it warm and cosy and this is with the A/C OFF. WITH A/C ON it feels even colder. I was thinking about trapped air but I was very cautious when filling it up. Before I'll check it again, I'd like to know what other experienced. In the US they recommend having the nose of the car down when filling.

My wife is always telling me I have a problem with trapped air but I am not sure she would agree with the solution on Prime.

[WhyOne?]

I don't think I have ever set my temp to more than 22˚C, more than hot enough for me.

Ditto.....

[Kaz-kzukNA1]

Thanks for the info, Kaz.

I don't know if it's just me but I think the heating capabilities of the NSX are inferior to other cars. I don't know if it's the mid-engine layout but I have to adjust to 28 degrees C or so to get it warm and cosy and this is with the A/C OFF. WITH A/C ON it feels even colder. I was thinking about trapped air but I was very cautious when filling it up. Before I'll check it again, I'd like to know what other experienced. In the US they recommend having the nose of the car down when filling.
For filling the cooling system, having the nose of the car down may help but because the coolant pipes and hoses go up and down at so many areas, I don’t know how effective it is.
Even keeping the car flat, I never had problem filling the coolant by following the procedure in the manual but you will splash a lot of coolant.
I want to keep my garage floor clean and don’t want to waste the coolant (because you need 16.0L + ), I use vacuum fill method but still, bleed small amount of air at the final process.



For the lack of cabin heat, interesting enough, I just saw almost exactly the same mixed feedback on this topic on NSX Prime.

http://www.nsxprime.com/forum/showthread.php?t=167983

Some of the information are not correct in that thread but as mentioned from NSXGB and Whyone, some owners are feeling like hot sauna whereas others have to raise the temperature setting.


I’m also the one with lack of heat.
This is even with the healthy CCU and no air in the heater core.
I didn’t spend much time looking into this because it doesn’t stop me from driving and I just raise the temperature setup and change the mode so that I can get enough heat.

I first noticed this more than 15 years ago.
I used to work in the area where it gets well below freezing temperature and every winter, you will get snow and once snowed, it won’t melt for a week.
One night, it started to snow while on my way back to home and because it was ‘wet snow’, it started to stick at the bottom of passenger side windshield after operating the wiper and also it started to create foggy/mist where the wiper couldn’t reach on the windshield allowing the snow to build up.
All this happened even the CCU was working fine and the solution was to stop the car, remove the snow from the windshield and then crank up the heater temperature.
I think the A/C compressor has shut down itself because it was so cold that the evapo temperature couldn’t reach above 3 – 4degC. It has protection protocol to prevent the evapo from freezing by disabling the A/C compressor operation when the evapo itself is too cold.


NSX has huge glass area for the size of cabin and I think it looses a lot of cabin heat through the glass.
Not sure this is the reason but if you change the mode manually to direct the air to the upper side (horizontal arrow on the display) and floor area, it makes the cabin warmer than letting the CCU to automatically (AUTO mode) select the air mode (normally, just blowing the hot air to the floor) even at the same temperature setting.

Heater core has its own coolant passage regardless of the state of the thermostat so this will allow the heater core to warm up first before the thermostat starts opening.

The CCU temperature control is very basic relying on several sensors and I don’t know what the state of outside temperature sensor after many years and miles.

If you use ‘fresh’ mode, the outside air temperature has big factor in the air temperature you will get through the vent.
Even you use ‘recirc’ mode, the seal around the re-circ damper door is dead by now so you can smell the exhaust fume if you follow the diesel truck which means you are allowing cold fresh air into the blower.
On my NSX with lack of cabin heat but perfect CCU and no air in the heater core, if I set the CCU at 32degC (this will force the water valve to open, stop A/C compressor, air aimed to the floor, fresh mode and max fan speed), it gets like sauna while driving so it’s not the lack of heat source but more to do with the air mixture control.

When I can find some time, I may spend some time to check the state of some of the CCU sensors.
Like on the dash instrument display (VR), there is an adjuster (sliding switch) on the CCU display module to increase/decrease the air mix control so you can try it but then you may need to think about what will happen in the summer.

Kaz

[Nick Graves]

My UKDM Prelude & S2000 have manual systems; you can feel the extra heat come through if you VTEC it...

[goldnsx]

Like on the dash instrument display (VR), there is an adjuster (sliding switch) on the CCU display module to increase/decrease the air mix control so you can try it but then you may need to think about what will happen in the summer.
I've already set it to +1.5 deg.

One question: if my coolant hoses to the heater unit have the same temperature as the ones to the radiator is there still a chance for having air trapped in the heater core?

[paulc]

Hi Kaz, well it looks like the water valve stays closed, there is no movement when you set the heater controls to 18 or 32 degrees. The silver aluminium pipe barely gets warm, I bled the system, some air in the system but not a great deal. Warmed the car up again, still no heating and the silver aluminium pipes still barely got warm.

One thing I did notice when going through all of the heating modes, when you set it to windscreen no air gets blown directly to the windscreen.

Have you any further advice??

Regards

Paul

[Nick Graves]

If you unclip the cable, can you operate the valve manually?

If it's working & not seized, then that'll save you £124. And you can leave it on hot for the duration.

Unfortunately, it probably means there is a problem with the actuator/CCU. You'll want a second hand one of those....

[goldnsx]

One thing I did notice when going through all of the heating modes, when you set it to windscreen no air gets blown directly to the windscreen.
I think your CCU needs a rebuilt.

[paulc]

I think you are right!!

[paulc]

Sounds like a cunning

Many thanks

Paul

[Kaz-kzukNA1]

My UKDM Prelude & S2000 have manual systems; you can feel the extra heat come through if you VTEC it...
This is the typical phenomenon on our NSX if you have lots of air inside the heater core.
The amount of coolant that can pass through the heater core depends on the water valve position and if you have lots of air trapped in the heater core, unless the water valve is fully open, it can only get hot coolant when the WP is working really hard, i.e., at high rpm.
Several NSX owners reported this exact phenomenon.




I've already set it to +1.5 deg.

One question: if my coolant hoses to the heater unit have the same temperature as the ones to the radiator is there still a chance for having air trapped in the heater core?
As in above, the amount of coolant that can pass through the heater core depends on the water valve position and the speed of coolant flow.
Therefore, even you have similar coolant temperature at the heater core and the radiator, still you may have small amount of air inside the heater core.
This is the reason why I always double check the air at the heater core bleeder after the test driving session if I work on the cooling system or engine refresh.




Hi, Paul.

Good to know that you managed to bleed the small amount of air from the heater core so that we can now take it out of the loop and you have now confirmed that the cause of no heating was due to the closed water valve.
If you need to drive your NSX under this kind of situation, you can disconnect the cable linkage from the water valve lever and just adjust the water valve manually around 50 - 70% of the stroke to get some hot coolant into the heater core so that you can warm up the cabin. You will feel mild - hot temperature at the silver aluminium return pipe.

You may have multiple issues so please take this into consideration when reading the followings.

There are several reasons for not being able to control the water valve.
The obvious one is that the cable linkage was not connected to the water valve lever and you will see it when you opened the bonnet.

As mentioned in my previous post, there is a chance that the other end of the cable inside the cabin where it is connected to the air mix control motor was dislocated if someone worked inside the cabin before you start experiencing this issue.

However, based on what you wrote, if you are not getting the air to the windshield when you selected the DEF mode, then there is a high chance that your CCU board is not working properly.

I don’t remember servicing your CCU board and I don’t know the year model of your NSX but if the CCU board was never serviced in the past, you may want to remove it and take a look at it.

If you see colour change at the base of each cylinder like capacitors, then you have a leakage.

You can see lots of examples by selecting the blog category ‘A/C CCU Board Service’ (http://www.nsxcb.co.uk/blog.php?1811&blogcategoryid=24)


If you think your CCU is fine, then I would test the air mix control motor.


Kaz

[paulc]

Many thanks Kaz, as far as I am aware my CCU board has never been serviced. My car is a manual 1991 JDM. What is the best way to remove the CCU??

Regards

Paul

[Kaz-kzukNA1]

Hi, Paul.
Wow, 1991 spec with no service history on the CCU……
You were very lucky that it survived until now.

For the removal instruction, I recommend visiting the website by user ID BrianK on NSX Prime.
I have never exchanged email with him but his service is highly regarded on NSX Prime and even for someone like me with Honda background, some of the info on NSX Prime are quite impressive.

Following link is the courtesy of his website;
http://nsxe-repair.com/CCUremoval.html

It is based on LHD model but you will get the idea.

You can also get the procedure info from the workshop manual.


The most difficult bit is the removal of centre vent under the clock module.
I recommend using the plastic cards such as your airline mileage club, etc instead of screw driver.
Please refer to the 3rd – 5th photos in #1 post of my CCU Computer board Service (http://nsxcb.co.uk/showthread.php?5940-CCU-Computer-board-Service-Part-1-3) thread in the Technical forum section showing how to insert the plastic card.
As your NSX is JDM like mine, the centre console has dark silver special coating and you don't want to scratch it.
The centre consol finish is different on UK model so you can't get the replacement from Honda UK.
Please be careful on removing the centre console especially around the audio head unit, CCU, etc where the frame work is extreamly thin.
It could break there or the coating may end up in wavy form if you bend the centre console too much.


You may have other issues on your NSX for not being able to control the water valve but if you look at the CCU board and find any leakages, just send me an email as I’ll be working on another CCU board very soon and I can work on yours at the same time.


Kaz

[paulc]

Many thanks Kaz, looks like I know what I will be doing this weekend. I will let you know as soon as I have taken the CCU out what condition it is in.

Many thanks

Paul

[paulc]

Hi Kaz I have now removed the CCU the condition of the board looks good, I think there is a small leak at C44. Are you happy to take it and service the board? If so can I have your contact details? One final question how do you remove the wires at CN3 and CN4, do the brown connectors just pull out?

Regards

Paul

[Kaz-kzukNA1]

Hi, Paul.

As I was busy with another project today, only managed to reply back to your ermail just now.

I’m expecting to start working on EPS controller in the near future and waiting for the owner to
send his controller to me.
I'm also waiting for some parts from US.
It’s taking bit extra time due to Thanks giving holiday season in US.

I must finish another CCU board (CCU Board B - ** in my blog) ahead of yours
so best to send the package around Wednesday this week.




https://lh3.googleusercontent.com/-oqltMpNnvP8/ULKrwdmXklI/AAAAAAAAGj4/9ghnbPXZ8_k/s640/IMG_0520.JPG
When handling the CCU, ideally, you should wear this kind of cable to discharge any static electricity.
If you don’t have one, please touch metal object such as your central heating radiator,
kitchen sink, etc and keep your body attached to it.

For the removal of brown connectors, you could carefully pull them straight up if you have
lots of experiences dealing with this kind of connector.










https://lh5.googleusercontent.com/-HdCv-qW-jCs/ULKrr9qjD-I/AAAAAAAAGjY/Vo9tEXFF7KU/s640/IMG_0514.JPG
If they are really tight, first remove the screw at the back.










https://lh6.googleusercontent.com/-X2fnNpvZ4CQ/ULKrtJ67twI/AAAAAAAAGjg/atKHD3qmnRM/s640/IMG_0516.JPG
Carefully lift the middle section of the CCU plastic case to pop out the centre stiffener plate.
In the above photo, upper section of the plate is about to come off.








https://lh6.googleusercontent.com/-u336X4h6qDM/ULKrvagWKRI/AAAAAAAAGj0/kIDDSfxPmRA/s640/IMG_0519.JPG
Slide out the board but make sure to keep your body attached to the metal object to prevent any
static electricity destroying the CCU board.
Please support the circuit board around the mating connector and then pull straight up the
connector with lots of wire to detach it from the board.


Please place back the centre stiffener plate and screw when sending the CCU board for
added protection during the delivery process.





...................... the condition of the board looks good, I think there is a small leak at C44................
I heard so many owners stating that the board looked fine with just small leakage.

Even the owner of the CCU board A - ** in my latest blog told me exactly the same and
almost everyone was surprised to see the extent of the damages once I started the service.


This is the reason why I take so many photos on any of my services as photo speaks itself.


If your NSX is 91 model, even without looking at your board, I have a feeling that it has severe damages already......

Looking forward to servicing your CCU board in the near future.


Kaz

[paulc]

Cheers Kaz can you please let me know where you would like it sent?

Regards

Paul

[Kaz-kzukNA1]

Hi, Paul.

As in my above post, I replied back to your email late last night.

It contains the delivery address, service request form, T&C, etc so if you haven’t received it by now, I’m afraid it is very likely that you don't have your latest email address registered to your NSXCB account.

Could you check it for me?

You can then send me another email and as a back up, please type in your email address manually inside the email body/content so that I can reply back to your correct email address.

Thank you.

Kaz

[paulc]

Hi Kaz,

Very sorry will check again. Just wondering if I did change my email address details, old age!!!

Regards

Paul