Air con not working properly

[Dipstickpete]

I am a new member with a 91 car and am having problems with the air con. It seems to work when the engine first runs, but then blows warm after a while.

I have just had the gas checked and it had already been converted to R134A so he checked for pressure, which was fine and then sucked out the old gas and replaced it with 900gms of new R134A. He seemed to think it was cooling up to about 750gms but the pipes then went warm at about the time the main engine fan came on, but that could be a coincidence.

I ran the diagnostics test yesterday and it indicated faults on E (the evaporator temperature sensor) and F (the Air mix control motor). Regards F the air mix door is definitely not stuck.

Anybody experienced this and can offer suggestions?

I am off to classic Monaco tonight, so hope the weather doesn't get too hot now!

Pete

[Pride]

Welcome aboard Pete.
Does the air coming through get warm when the air conditioning is turned off???
And if so does it stay warm when you turn off the auto climate control???

[Dipstickpete]

Pride. Temperature doesn't seem to change whether on or off and no different on full auto or manual mode, so I suspect a sensor problem, as it is definitely working when the car starts from cold.

[Pride]

In that case I'm about 90% certain the climate control module in the dash needs an overhaul due to leaking capacitors, it's quite a common fault on early cars and can cause all sorts of different symptoms, not just air temperature.

Our technical guru to confirm this would be Kaz who also offers a speedy turn around service for it although tomorrow would be asking just a little to much even for him.

Have a great trip with windows down.

[Dipstickpete]

Thanks, I'll contact Kaz when I get back, but how do I do that, assuming he doesn't read this?

[Pride]

Thanks, I'll contact Kaz when I get back, but how do I do that, assuming he doesn't read this?

You can personal message, him but to be honest he usually reads and replies to most postings when necessary, particularly technical issues which is good.

[Kaz-kzukNA1]

Hi, Pete.
I’m afraid if your evaporator sensor is flagged as failed, the a/c compressor won’t engage.
There is fail safe algorithm in the CCU that if this sensor was detected as faulty, it will use -1degC as the evapo temperature.
If the evapo temperature is below 3 - 4degC, the CCU software will disable the a/c compressor and thus, no more a/c.


You can see whether your compressor is spinning or not (compressor CL engage/disengage) by monitoring the pressure plate while the engine is running.
In fact, you can check this without running the engine by watching the changes in the tiny clearance (0.5mm) at the pressure plate but if you are not familiar with this, it’s much easier to check while the engine is running.
If you can’t see the pressure plate spinning together with the pulley, your compressor is not engaged and thus, no a/c.

The evapo sensor is a thermistor so very unlikely to fail on its own unless it was knocked or connector disconnected.

If you had your CCU serviced or removed recently, please double check that both green connectors at the back are fully locked.
On some NSX, they were only partially locked resulted in intermittent connection.

Not sure how you checked the air mix motor and confirmed that the air mix door is not stuck.
You can’t see the spiral shaft movement from outside.
You can see the water valve movement under the bonnet though.

Kaz

[Dipstickpete]

Finally starting to get somewhere, whilst removing all the internal fittings to strip out unwanted added 1990 hifi equipment. Passenger footwell underlay was sodden and I suspect evaporator is not draining even though drain is clear. Will take blower off tonight and give everything a good clean, as suspect it will be full of crud. Can I also remove the sponge from the side, as this is very wet, and is this where water leaks from? Where is the evaporator sensor if this is suspect?

Having reconnected all the sound system cables to original positions only the door speakers work weakly, how can I test the floor bass system? If it is knackered what can I use as a replacement and where do I get it? Not after super hifi, just a sensible original radio with blue tooth input, I'd generally rather listen to the engine note!

Can't believe how easy it is to remove everything, so much easier than a 1969 TR6! And it still drives with everything stripped out.

Pete

[goldnsx]

water leaks

Check your door seals.

[NSXGB]

If they have never been serviced, I would get all three amps serviced whether they are working or not at the moment. They will die....