A/C intermittent problem

Joined
15 September 2004
Messages
137
Location
RI
Help! My A/C compressor keeps shutting down (91 5 speed). I can drive about 1/2 hour and then the compressor shuts off. Then it is on for a short time, maybe 5-15 minutes, and then off for about the same amount of time, and will cycle like this. The other day I drove on I95 for 35 minutes with it working fine, cold air, then it shut off and started cycling. It was only about 70 degrees.

The local mechanic recently found two leaks and fixed them, but it still has the problem. I think the system is charged properly now, but the problem persists.

I did a search but at this point I need some direction on how to troubleshoot this problem. I have a copy of the shop manual.

A few years ago Brian K did the capacitors for the climate control unit, as a precaution, I had the dash apart and figured it would be a good time. The fuses for the condenser fans are good, and they seem to work right.

Any direction on this issue would be helpful.
 
when your at idle with a/c off when you press the A/C on
do you here a click behind you, then your rpm's will go up a little?

then your a/c compressor is working,

while the a/c is on, walk in front of the car and put your head down under both headlights, do you here the fan/fans going? there are 1 fan on each condensor so total 2 in the front if one or either are spinning then your fans maybe bad.

when the a/c in on is one side colder than the other?
then its not fully charged.

when the system is low only the passenger air volume will be cold and the driver side warm.

check those and report back
 
It could be a number of things but is likely just one. before you start hopping around the problem like Bugs Bunny I suggest you start by using the manual you have. (good idea having one):wink:

The climate control unit has a self diagnostic circuit check feature.
It can point you to a faulty component in the system chain.

Go to pages 22-12 and 22-13 of the service manual. Read it carefully and perform the test procedure and decipher the results using the legend on the bottom of the page.

See what this finds, if anything, and go from there.
 
Ok, I started the car this morning and the a/c compressor would not turn on.

Then, I did the self diagnostic tests as Joe advised, and the system functioned properly (including turning the compressor on), there were no faults indicated.

I checked the condenser fans as Shaun advised, and they were running at the same time the compressor would run, so they seems to work ok. Both sides of the dash had cold air. The compressor was now running properly, cycling on and off for maybe 15-30 second intervals.

It seems strange that the self diagnostic test made the compressor work properly, or maybe just a coincidence. I could try to duplicate this again. That is, run the car until the compressor stops working, run the diagnostic test, and see if the compressor starts working properly again.

Thanks for all your help so far.
 
I dont see how putting it in self diag mode fixed anything?
you said its working proper now. so wait and see if the prob returns.

Pbassjo knows his stuff so it worked, problem solved

so anyone with out the service manual here is the quote from those pages.

" The Automatic climate Control System has a built-in self-diagnosis feature. To run it, Turn the ignition switch ON and turn the fan switch
to AUTO postion. Wait for atleast one minute on each temp display 18C(64F) 32C (90F). Then push both the AUTO and OFF buttons on the control unit at the same time. Any Problems in circuits "A" through "I" listed below will be indicated by the respective indicator coming on.
The climate control unit does not memorize which self-diagnostic indicator lights come on. If you turn the ignition switch OFF, the indicator light memory will be lost"
 
Update, the problem returned. I tried the self diagnostic test again and it did not restart the compressor, so that test probably didn't have anything to do with the problem.

Brian, I'll try to isolate the problem at the inputs to the fan control unit.
 
I have see some strange issues caused by the fan control. My own car has the compressor runs all the time problem. Re-soldering the connector pins on the fan control unit board helped but I still suspect connection issues in the connector.
 
I have the exact same problem. Started the car, turned on AC, nothing. Drove for about 10 mins, AC turns on. I can hear the condenser fans going. Everything was good. 10-15 mins later, AC stops but the AC is still "ON" according to the CCU. All condenser fans are off.

Not sure what is going on here. My CCU has been repaired.

Brian, when you say re-soldering the connector pins on the fan control unit board, are you referring to the board behind the fan knob?
 
I have the exact same problem. Started the car, turned on AC, nothing. Drove for about 10 mins, AC turns on. I can hear the condenser fans going. Everything was good. 10-15 mins later, AC stops but the AC is still "ON" according to the CCU. All condenser fans are off.

Not sure what is going on here. My CCU has been repaired.

Brian, when you say re-soldering the connector pins on the fan control unit board, are you referring to the board behind the fan knob?

Brian is referring to a fan control unit behind the passenger seat. It's a small control unit which is like a commander for the fans and a/c compressor. I disconnected it to get at the connector, and can access inputs like the triple pressure switch. I plan on monitoring some of these inputs to try and figure out what the problem is, with a vom.

Stay tuned.
 
It turns out that the "connection" to the fan control unit is quirky. With the AC set to "OFF" on the CCU, the AC turns on and off (the condenser fans spin) when I jiggle the fan control unit connector wires. I have yet to remove the unit and open it up to see the connections inside.
 
It turns out that the "connection" to the fan control unit is quirky. With the AC set to "OFF" on the CCU, the AC turns on and off (the condenser fans spin) when I jiggle the fan control unit connector wires. I have yet to remove the unit and open it up to see the connections inside.

Interesting. I will have to try that. You need to take out the center rear speaker section to get at the fan control unit.
 
I'd consider trying the tests on page 22-59 for the pressure sensor.
 
Last edited:
Ok, problem solved. I replaced the fan control unit with a new unit from acura. Ran the car several days, enough to know it is working properly. I do not have the skills to get into the internals of this unit, so replacing was the option for me.

Tried several tests, but the most convincing was playing with the connector while the car was running, and was able to shut the compressor off and on, but only intermittently, like the problem itself. One test was as Joe suggested was to see if the hi/low switch, part of the triple pressure switch was working ok. I was able to test with a VOM at the fan control unit and it proved to work ok, when the compressor was not running.

dablackgoku, you seem to have the same problem and solved it by repairing the fan control unit. As I said, this is beyond my skills, but importantly, we have identified a problem which may be similar to others on this board, or potentially, in the future.

Briank, if you want, I will send you my old fan control unit (free). Maybe it would help others as as a core unit for future replacement.

I don't think I could have solved this problem without the help of the board members. NSXPRIME rocks:biggrin:
 
Nice job. You diagnosed the problem and then repaired it instead of throwing parts at the car until something worked.
A big "atta boy" and congratulations to you.
 


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