AEM and climate control

[boca rat]

(Note I moved this from the DIY forum as appears to be AEM related).

Urgent: AC not kicking in after new compressor etc

Recently acquired a 91 CTSC with series 1 AEM. AC has not worked (i.e. it was leaking) in a long time apparently, likely from before the AEM/CTSC was installed. New compressor, condensor, from the dealer (they still have the car), all runs fine when powered directly, cools fine, no leaks etc. But doesn't work when run through climate control.

When I got the car, fan blew on max or nothing, so sent the board to briank, got it back (actually he sent me a board, i returned my old core), installed and blower worked fine.

Update from dealer - they swapped in an OEM ECU from another 91 and all works fine so it appears that the AEM is the culprit. It's unclear if this is programmed this way, if the AEM is faulty or not even hooked up right. I am totally new to the AEM/FI world so could use some advice.

I just ordered an RS232/USB adapter, and will download the AEM software and hook it up. But am pretty nervous about touching anything. The car is due to go for a dyno tune in two weeks to the original tuner (Mase in Jacksonville) so will likely wait until then but meanwhile are there NSX AEM 101s out there?

Any other advice?​

 

[DDozier]

This should be easy enough to diag. The CC Unit sends a request to the ECU to run the AC compressor, this way the ECU can turn off the compressor at a given RPM to prevent damage to the compressor at higher RPMs. If you can get the tune out of the car and post it up someone here will take a look at the tune and see if the outputs are configured correctly to run the AC or if the output has been disabled. It is most likely disabled. There is a possibility the AEM ECU itself is damaged but not likely, since the rest of the system checks out if the AC system runs on a known good ECU this should be an easy fix.

Mase can handle the issue as well just make sure they know what issues you are having, before the retune.

Dave

 

[boca rat]

Thanks Dave, will check back in with the results of the tune. Thanks for chiming in

 

[Jinks]

Have you ran the climate control diagnostic to see what the issue is? The ecu is completely separate from the climate control. I would run the test.

 

[boca rat]

Jinks, so if it's completely separate, how come swapping back in a stock ECU fixed it? Not sure I understand. Didn't know those diags were out there though.

 

[DDozier]

The climate control determins if you are in heat or cool mode and controls how the air blows and blower speed. If the CC determins the AC needs to run it requests the ECU to activate the AC compressors clutch. If the ECU does not want the compressor to operate it will not. The ECU will shut the compressor off for several reasons like RPM or engine coolant temp. Almost every car is set up this way.

Dave

 

[Jinks]

The climate control determins if you are in heat or cool mode and controls how the air blows and blower speed. If the CC determins the AC needs to run it requests the ECU to activate the AC compressors clutch. If the ECU does not want the compressor to operate it will not. The ECU will shut the compressor off for several reasons like RPM or engine coolant temp. Almost every car is set up this way.

Dave

You learn something new everyday. So the ac runs through the ecu. No Sh&t, I would have never known. Thanks!

- - - Updated - - -

Dave, so are you saying if I choose to go with a stand alone later on with my ctsc, I have to program my ecu to run the hvac compressor?

- - - Updated - - -

Jinks, so if it's completely separate, how come swapping back in a stock ECU fixed it? Not sure I understand. Didn't know those diags were out there though.

You can pull up the cc unit test from the wiki here as I have done. It may be something simple to fix or it may very well be the ecu. I am unsure of this. But the test takes a few mintues and it's free.

 

[boca rat]

OK, dyno tuned today by Mase and he also got the AC running. Earlier today I hooked up my laptop running AEMPro and could see that the AC clutch was disabled, but the drop down of choices was intimidating so I left it to Mase to sort out. If anyone needs to know exactly what the AC settings are on my car, let me know. I am a much happier camper now....

And before anyone asks, 377rwhp with fuel delivery problems at the high end (6500rpm+) so either need a new fuel filter, or maybe a new pump (which is not fun, has a Walbro right now). Plan is to add a fuel pressure gauge by the motor and see what it says before and after the fuel filter is swapped out as was last done in 2007, 21k miles ago. Then go from there. Intercooler seemed to be doing it's job, air temp was pretty steady for each run which was 'cool'.

Thanks to all who chimed in on this.