Our '99 Civic's air conditioner blows warm when car is idling. Shop said it needs new "A/C thermostatic switch", and said that, until replaced, a work-around is to keep engine above 2000 RPM when stopped. They said they couldn't replace that switch because it's been discontinued by Honda and other manufacturers.

Sounds like it might be a switch that turns on the condenser fan when at idle, but I'd like to be sure, so I can find a used one. Anyone know what this is?

Extra bonus points for a picture, diagram, or OEM part number. Thanks!

-- Jeff

 

If your thermostatic switch were bad, revving the engine would NOT help.

Find a shop that knows what they are talking about.

 

Listen to mk.

Does the condenser fan run when the A/C is on?

 

MK - It is possible the shop mechanic is mistaken.
Ron - Yes, the condenser fan runs when the A/C is switched on, even when sitting at idle, and the fan turns off when the A/C is turned off. Driving down the road, the air blows cold, but warms up noticibly after stopping and sitting at idle, or when driving in very slow traffic. Put it in neutral and get the RPM up above 2000, and it gets cold again. This is after new compressor, new dryer - prior to that, it would only get cool at best, even when fully charged. From your diagram (Thanks!!), I bet the mechanic was referring to the A/C thermostat. That would fit w/ what he told me - the OEM part number for that is 80430S01A21, and four different parts distributors show that item is discontinued by the manufacturer. To MK's point, I don't know how it would be affected by idling, but then I don't know everything that goes on inside the computer module.

So, I think I have the answer I needed - I found drawings of that part and know where it's located on the vehicle, so now I can hunt for a working unit and make my wife happy by giving her all the cold air she wants.

I'll definitely keep an eye here in case you have any feedback or anything else to add. Thanks again for your help.

-- Jeff

 

All day, every day.

As mk stated, a bad thermostat is unlikely to cause the symptoms you describe. Be very skeptical about what the mechanic tells you.

When the A/C blows warm, does the fan stop running and does the compressor clutch disengage?

I fear you'll be disappointed by the outcome. Did the same mechanic replace the compressor?

 

Did the shop replace the drier and expansion valve when they replaced the compressor?

 

Ron - When the A/C blows warm, the condenser fan keeps running. Haven't watched for compressor clutch disengagement - I'll check that tomorrow.
Ron & CK - The shop replaced the compressor, condensor, and expansion valve.
All covered by 24-mo warranty (parts & labor), and told me that they'll put the "thermostatic switch" in if I find one, but, since they've left me with more questions than answers, I think I'll make time during lunch one day to run over there and see if they can shed some light here.

Y'all are the best, and I appreciate your help.

-- Jeff

 

The A/C thermostat is a simple on/off switch, [turns on compressor and condenser fan] if it was the problem then the condenser fan would not be running when air is warm.
FYI it is behind the glove box it's capillary is pushed into the evaporator through the evaporator box.
Shop should have known they did not have to use a Honda one, there are more then a few universal ones that would work, but then again it is not the problem.

The only things that produce those symptoms are either a low refrigerant charge, a bad compressor, a bad expansion valve or an air flow problem.
A fan in front of condenser or even cold water hosed over the condenser when at an idle will tell you if it is an airflow problem.
A set of A/C manifold gauges will tell you if it is a low charge, the expansion valve or the compressor, the shop should have known that.

Was it an OEM or OEM replacement compressor, a new compressor or a remand compressor ot one of those cheap made in China copies?
Also was the accumulator/filter replaced I did not see that on the list.

My guess is the problem is the compressor, not compressing properly at the lower RPM. 94

 

I visited the shop & spoke to the technician. First, I should note that, before they even worked on it, the A/C was blowing warm at idle. It also wasn't cooling very well even at best, though, and two shops told me it was the compressor. So, the 2nd shop did the work - replaced all the stuff I listed (accumulator/filter isn't listed among the items), and it blew nice and cold. During test drives, though, they found that it was warming up during idle. The tech said they narrowed down the cause as either a faulty ECM or thermostatic switch (and verified that "thermostatic switch" = OEM P/N 80430S01A21), and that the switch was far cheaper than the ECM, so best to try it first.

Tomorrow, I'll take a look and see if the compressor clutch disengages at idle.

Perhaps a different shop could've pinned down the cause exactly, but I found that switch on Ebay for $15 w/ a 30-day return policy, so it'd be pretty inexpensive to try it and see if it solves the problem, even if a long shot. . From your input and Ron's circuit diagram, though, it's looking a lot more likely that it's the ECM.

-- Jeff

 

Study the circuit diagram carefully. A bad ECU or thermostat would yield completely different symptoms, again verifying that your mechanic is either incompetent or a scammer. You decide.

 

The ECU will drop out the compressor if proper idle speed can't be maintained. This helps avoid the worse situation of the engine stalling out. If that is what is happening there is an engine problem not an A/C problem.