AC not cooling

[PostVW]

I
bought my NSX -92 in January and now when it´s the warm season there is no cool air coming from the AC at all.
I had the tightness of the system tested and all was OK, they pumped vacuum and then filled with new gas (r134 -it´s a converted system). The compressor is working well but there is a stop somewhere in the pipings, no cirkulation. They told me that the Expansion Valve is a common problem-part on most car models. Anyone having some more ideas?


Read about the time-wasting job to remove the Heater-evaporator unit which incuding removal of the the dash and have a question:
Can you do replacement of the Expansion valve from the front department (firts removing the Blower) without stripping the dash?

[Mark N]

Problems with air-con contact Kaz or read his posts on here. He is the man to fix the problem especially if its the circuit board.

Mark

[duncan]

Replace expansion valve from the front of the car - yes.
It's fiddly as a thermometer bulb is wrapped to it, but do-able.
The valve can be bought as a generic part, sub £30 [excl VAT] in 2010. Once the system is opened up the reciever/drier will also need to be changed as it will have picked up atmospheric moisture, again available as a generic part at about £20 [excl VAT].
Mine were supplied by Motor Climate Services, 66-102 Cherrywood Rd, B'ham, B9 4UD. 0121 766 5006. Usual disclaimers, but they do know what they are doing.
See the attached service bulletin, it details the thread forms for the different years of manufacture.

[Kaz-kzukNA1]

If the expansion valve is not responding properly,
your A/C specialist should be able to see it at the pressure gauge.


The most common mode for expansion valve failure is almost no pressure at the low side gauge and
from time to time when the valve decides to operate for a short period, you will see some pressure
at the low side and you will feel some cool air briefly but after that, back to no cold air.


As duncan mentioned above, you can replace the expansion valve
by removing the blower motor fan.

It's the brass colour one.

https://lh4.googleusercontent.com/-4HycUnpU6rE/T0ocbBvFSaI/AAAAAAAAA2U/6_f7AwTvjYo/s400/IMG_0179.JPG


However, quite often, the hex nut is really seized and tries to rotate the whole valve/pipe assy and
you will have difficult time removing it.

The pipe from the evaporator is aluminium and the pipe diameter is not that big.

Therefore, if you apply too much torque, you will twist and damage the pipe requiring
the removal of evaporator that means you must take the entire dash board out.

Also, you need to be very careful not to touch the evaporator fin as it is very fragile.


Unless your A/C specialist has confirmed that the expansion valve has indeed failed, I would
first check the basic things such as the operation of R & L condenser fans, CCU and
double check that the compressor CL is indeed engaged.

You can see the operation of the compressor CL by looking at it down below the engine bay.

Quite often, the two 10A fuses for the R & L condenser fans inside the pentagonal box under
the bonnet are blown and you won’t get cold enough air when the car is not moving or at very slow speed.

If you haven’t refurbished your CCU board yet, the capacitors on 92 model is
almost 100% leaking.



You can use the CCU function and operation check method in the workshop manual to force the
CCU to switch ON the compressor regardless of the sensor input.

Having said this, if the evaporator temperature is below 3 – 4degC, the compressor will NOT engage
even if you manually pressed the A/C ON switch.

[Edit: Also, please check the operation of the water valve while using the above test procedure.]


Kaz

[PostVW]

I have now checked the fuses for the condenser fans (=OK) and also run the CCU tests without any error indications. During the test I could hear a click from the compressor behind me. So everything seems to be working but it´s not cooling. Any ideas for my next step?

[Kaz-kzukNA1]

Hi, PostVW.

Presuming that you visually (not just by the clicking sound) checked that the clutch at the A/C compressor was spinning when the ‘A/C ON’ was displayed, the water valve was set at the correct position depending on the temperature setup and you have the right amount of A/C gas in the system, then as suggested in the above post, please have your high/low pressure checked by the A/C specialist.

It is not that common to have water valve issue but I saw the linkage cable installed in a strange way after someone worked inside the cabin, the locking tab of the cable behind the water valve becoming loose and allowing the cable to detach itself from the valve, etc.

Please make sure that the water valve is moving freely and at the correct position because you won’t get cold air if it was stuck at the hot side.
You can check this by touching the heater core coolant return pipe with the bleeder plug on top.
When it is at hot side, please be careful because it is really hot and you should not touch it for more than 0.5 sec.

The direction of the water valve operation is opposite between RHD and LHD model.


Not sure where you are based but presuming your air temperature is around 20 – 25degC, you will see about 1 – 2Kg/cm2 at the low side and about 9 – 11kg/cm2 at the high side but your A/C specialist should know this any way because our A/C system is nothing special from the point of operation mechanism compared to other cars.
It will show similar figures as other cars.

Expansion valve failure, receiver blockage, etc to be checked.

Tripple pressure switch is fine if you can confirm that the A/C compressor clutch is spinning while the ‘A/C ON’ was displayed.


In Japan, the summer is very hot (over 35degC) and very humid that without the A/C, it is very uncomfortable to drive NSX.
Due to the age of our NSX, lots of NSX are visiting the NSX specialist in Japan for A/C repair around this time of the year because the owners started using the A/C more frequently as it’s the rainy season at the moment.

The CCU board, compressor and expansion valve are one of the common failure parts so most of the NSX specialists in Japan are stocking these parts together with the receiver and O-rings at their places.

In fact, compressor and expansion valve failure are popular on other cars as well.

These parts are very unlikely to fail all of a sudden and normally, there was a sign/symptom of failure in the past.

For example, if you kept running the A/C system with gas leakage, you were very likely to loose the compressor oil as well. This oil attracts moisture and very sticky. Over the years, the tiny air hole will allow the contamination and even block the receiver.

No need to tell that it will harm the compressor with lack of oil.


So, it is always important to service the A/C system at the first sign of the issue especially if your compressor started to make even a small noise.

Running the A/C regularly is also an important factor.
Even in the winter, it is very important to run the A/C even for a short period to keep the system healthy.

Hope you can fix your A/C issue soon.


Kaz

[goldnsx]

The pipe from the evaporator is aluminium and the pipe diameter is not that big.

Therefore, if you apply too much torque, you will twist and damage the pipe requiring
the removal of evaporator that means you must take the entire dash board out.
There are counter-threads on the valve itself, use them. ;)