another A/C problem...

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20 September 2003
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I looked into the faq, and did a search... (see how scared we are to start a new thread..... ) :-)

A/C compressor doesn't stop. even with the airco-computer switched off, the relay stays powered.
This means that the first 100miles everything goes great, but than the system starts to freeze up and no air is comming out the outlets anymore. That's how I found out about this problem.



Anyone had this problem before?


thx,
 
I would pull the climate control board and see if any of the caps have leaked. When my board was bad, the AC actually started turning itself on without human assistance.;)

Good luck
 
If I look at it right, the clutch get's its +12 directly via the ingition key. The ground is provided by the PGM FI computer. So the relay is 'ground-steered'. Why does the PGM FI computer steers the relay and not the AC-computer?? Probably because when the AC-computer gives a 'go for it signal' the PGM FI looks at some engine settings before it will steer the relay. (engine not at full charge, going to a richer idle...). I see a lot of work for me to be done in the next week :-(
it's a hobby
 
Not quite sure I understand Bart. The AC compressor firing up shouldn't depend on engine being warm or cold. The climate control board should tell it to open the circuit.
 
hlweyl said:
Not quite sure I understand Bart. The AC compressor firing up shouldn't depend on engine being warm or cold. The climate control board should tell it to open the circuit.

nothing to do with engine being cold or warm, but other settings are looked at. As I said when the engine is at full charge (fast acceleration) the PGM FI computer will hold on grounding the clutch. Have you ever noticed on any other HONDA your acceleration time from 0 to 60 is not the same with or without A/C. A/C takes power away. Not with the NSX, it senses full charge and the PGM FI computer will not allow for the A/C compressor to run. Have you ever noticed on any other HONDA at idle, if you switch on the A/C and the compressor engages, there is a noticable drop in engine idle speed? Not with the NSX, the PGM FI computer will enrichen the mixture or switch over to a higher idle RPM, so that when the clutch engages there is no difference in idle RPM.

But this doesn't fix my problem ;)

I have a constantly grounded relay... let's start measuring. :(
 
i've been having this exact same problem as of late but it has been somewhat intermittent. i have yet to troubleshoot the system at all but i have looked over the schematics for the compressor clutch circuit. i was hoping that the compressor clutch relay had a sticky contact but i will need to investigate further. please post any findings as it would be very helpful. -paul
 
All Hondas have the airco clutch controlled by the fuel (PGMFI)computer, this is mostly done for the problems when idling.I do not know about the full throtle system, not on a legend ...
Maybe someone can try this??

Have you tryed running the engine (AC switched off),disconnect the wire to the clutch (Near front cylinder bank), then switch on AC.
Does the idling RPM increase?

Second test: what happens if you switch the relay for the fan relay.Does the fan keep on turning??

Third thing, maybe the high pressure switch in the AC is defect
 
after doing a lot of reading/searching, i have not yet found a similar thread for an a/c problem with these symptoms. i have found numerous threads talking about failed capacitors but the symptoms appear to be a little different (blower motor, display, etc). could this still be a capacitor issue but maybe a less common one? -paul
 
unfortunatley not, i have pm'd back and forth w/ BrianK to help diagnose it but have been unsuccessful thusfar. i tried one of BrianK's upgraded boards and it made no difference. where we left off was the possibility of the refrigerant (R-12) level being low which may cause this odd condition. have not recharged it yet.
 
I don't believe its a low R12 issue. My compressor was replaced due to a leak and my system recharged and the problem is still there. I had someone suggest that it was my ECU but I am not sure about that.
 
There could be some truth to the ECU failure potential. I haven't looked at the the schematics in the manual in a while but I believe the a/c on signal goes from the climate control board, through the ECU then to the a/c compressor clutch relay. There was another prime member that had a similar problem and he fixed it by swapping over a component that failed in his ECU, his symptoms were similar but not exact. I did have a ZIF socket installed in my ECU a while back so it has been opened up. The only way to know for sure is to find the infamous "known good ECU" mentioned in car manual troubleshooting sections to swap it out and test. I have been meaning to try to borrow one locally from someone who may have one floating around but never started asking around. I have been pulling my a/c compressor clutch relay when at the track to make sure the compressor doesn't load the motor when it is not supposed to.

HTH,
Paul
 
The compressor run signal goes from the CCU to the fan controller and then to the ECU and then to the compressor clutch relay. The fan control uses the signal to know when turn on the condenser fans and it also will cut the signal if the Freon pressures are too high or to low. The ECU uses the signal to know when the compressor is running so it can modify its idle control for the increased load on the engine and it may also cut the signal at full throttle to increase performance.

For this problem the fan control is the most likely area where the signal is getting messed up. IMHO
 
I looked into the faq, and did a search... (see how scared we are to start a new thread..... ) :-)

A/C compressor doesn't stop. even with the airco-computer switched off, the relay stays powered.
This means that the first 100miles everything goes great, but than the system starts to freeze up and no air is comming out the outlets anymore. That's how I found out about this problem.



Anyone had this problem before?


thx,

I have just started to have this problem... Anyone know the root cause of the issue???? I'm thinking about replacing the ac compressor relay to start.
 
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