CCU test procedure

[m666 edd]

I recently got my CCU board serviced and wanted to check that it is working OK so I tried to do one of the test procedures as per the service manual:

"The Automatic Climate Control System has a built-in self diagnosis feature. To run it, turn the ignition switch ON (II),
then turn the fan speed dial to the AUTO position. Set the temperature control dial to 60° F(18°C), then gradually move
0the dial up the temperature range to 90°F (32°C). At each temperature setting, push both the AUTO and OFF burtons
on the control unit at the same time. Wait for at least one minute for the system to readjust and check for problems.
If any problems are found in circuits "A" through "I", the system will indicate which circuit has the problem by lighting
the respective indicator light."


When I do this should I see anything happening or any indication the test is in progress? I think a long time ago I tried this and I thought something happened to indicate it was running. It was too hot to sit in the car and fiddle around so I gave up after a while.

Separate to this I want to get my air conditioning to work as the clutch isn't engaging but I believe this is probably because of low freon due to lack of use.

[NSXGB]

It should run through the different air vent modes and operate your water valve under the bonnet.

[Kaz-kzukNA1]

The self diagnosis procedure is to check the input and output to/from the CCU board so it won’t be able to detect some of the failure modes unless the CCU brain has actually sent out the command and also there is a feed back loop for it.

Because of this, when I service any of the CCU boards sent from the owners, I’ll run Function & Operation test procedures and other scenario testings using my hand/face/eye to physically and visually check the actual air flow, temperature and the vent modes.


During the self diagnosis process, if the CCU didn't detect any failures, then nothing will happen.
Or, let me phrase it properly.
Nothing on the display module will change.


If you refer to the attached pdf file, you will see the specific input/output circuit modules (shown as circuit A to I) that have the self diagnosis feature.

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If it fails, it will trigger the specific indicator on the display module.

If your centre console is still loose, then you can disconnect the IN-CAR temperature sensor (cabin temperature aspirator fan sensor) connector and it will show the text ‘MODE’ on the display so that you know you have carried out the self diag process properly.
Or, you can go to the front bumper and disconnect the outside air temperature sensor if your centre console is already back in place.
For this, the ‘defrost marker’ will show up on the display during the self diag process.

Having said this, I know your NSX is lowered so you may struggle to access this sensor connector.....

It is important to run the Function and Operation test and feel for the air flow as well as visually check the movement of water valve, VENT, etc so I will attach another pdf file below.

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If your compressor CL is not engaging, then it is possible that you have too little/much gas in the system.
Without running the engine, you can just bypass the A/C CL relay to listen for the 'click' so that you will know the wiring side is fine.

Good luck.

Kaz

[m666 edd]

I must have been remembering the Function and Operation test. I'll give that one a go and check it all first hand. From the trip to North Wales and back all the fan modes and vent modes seemed to work as expected unlike before the CCU repair.

If bypassing the A/C CL relay works I'll get a mobile A/C guy round to check out the system and re-gas.

[Kaz-kzukNA1]

If bypassing the CL relay, as mentioned in my post, please do so without running the engine.
There is a reason why the relay is not engaged (Engine ECU and Cooling fan control unit monitor the a/c triple pressure switch) and you don’t want to run the compressor with too little/much a/c gas in the system.

Kaz