Hi People!

OK I have a '94 with ~138K miles. On a cool morning like today (60 F), the A/C will come on and cool. The condenser fan turns on and I hear a loud click when I turn on the A/C. However as the day goes along, around 75 F or so, turning on the A/C results in the click and the fan turning on but just for a few seconds, and it goes back off. When I first got the car (summer a couple years ago) it worked ok, and as time went on, it got more and more problematic. My non-expert guess would be that the system needs to be recharged. But the ECU is a black box to me so..

Is that clicking sound the clutch of the compressor? or is that just the relay for the condenser fan? I can't tell visually if the compressor is engaged (don't know what I'm looking at). That is, I see the pulley spinning of course...

Now here's the really strange part, the recirculation and fresh air buttons both work fine and do what they're supposed to do. I can go back and forth between them and the redirection back in the dash happens as expected. Let's say it's set to recirculate and the A/C is turned on, but the condenser fan is not running (hot day, hot output air). If I push the recirculate button in, HARDer than normal, the A/C will try to kick on (the fan spins and i hear the click). Over the last year, doing this sometimes would get the system to stay on while I was driving, and other times it would just work for a little while. If I got it to work, then stopped somewhere, then within an hour drove it again, it would be more difficult to get it to work. More recently, I would have to hold this button in (and not just pressed, but you have to press it a little harder than you'd normally do) to keep the system working. Most recently, this doesn't work beyond getting it to make that initial click (and, I presume, the short period of the condenser fan spinning).

to get the functions for recirculate and fresh air to work, you only need a tiny bit of pressure. But again, on cool days, the system would work fine, although the output is not as good as it was 2 years ago.

BTW, I suppose this thing takes R12? Is the only way to charge it to go to an A/C repair shop? Where can I find low side/high side gauges for an R12 system? cost? I did just now get the service manual, so I will go through the steps of checking continuity and checking that switches are working before I do anything else. Just wanted to get y'alls' opinion.

 

If the fan doesn't run either you have a control problem. If it is undercharged the fan will run but the compressor will not engage. Most likely the control panel itself is defective since you could apply abnormal force there and make it work. There is also a thermal control on top of the evaporator box. If you remove the glove box you could tap on it and see if that makes the system work.

For future reference you can tell if the compressor is engaged by looking at the spring plate on the end of the unit next to the pulley. If engaged that spring plate will be spinning. If not engaged only the pulley will be turning, the spring plate will be still. You probably can't hear the relays from the driver's seat. The click you hear is the compressor engaging.

Your car should use R-134a. In the USA R-12 was discontinued after model year 1993 (and most of the 1993's are also R-134a). Do not just add refrigerant without measuring both the high and low side pressures before and during the charging process. Again this is for future reference. You probably need a new control panel inside the car.

 

Thanks for the reponse.

just to reiterate -- the extra pressure method does not work anymore. It will engage the compressor and fan but just for a moment then it won't usually come back. Is there a way I could eliminate or isolate the panel as the problem, say by disconnecting a harness somewhere and jumping across the pins?

Where do savvy folks like yourself find old replacement parts?

Also is it possible to tell if it's using R12 or not? The person I bought the car advertised it as having the older system (they said it was colder than the newer R134a systems). Will an R134a recharge can connect to an R12 valve?

 

I think it is just one wire from the control panel that gets grounded to engage the A/C. When the fan is on any setting other than off and the A/C button pressed, the wire is grounded. The recirculate buttons don't have anything to do with it. I don't have the diagram in front of me to tell which wire though.

As for whether you should use R-12 or R-134a if you need any, which I don't think you do, the valves are different. Locate the service valves on the lines at the condenser and unscrew the plastic cap. If there are threads on the outside of the fitting and a conical top it is a R-12 fitting. If the threads are on the inside of the fitting, the top flat, and a locking ring for a quick disconnect, it is R-134a. Put the caps back on to prevent leakage.

Someone may have been mixing and matching parts though. A 1994 would've definitely been equipped for R-134a if fitted with A/C when sold new. If it looks like someone has been mixing and matching you should go to a shop that has an analyzer and have them test to see what refrigerant is actually installed.

Don't recharge right out of those cans with a hose in any case. Buy a gauge manifold (about $75) to charge it yourself so you can watch both pressures and not overcharge it. Also never put in any sort of "high mileage" or "leak stop", that will cause a lot of trouble later.

 

gotcha.
Yeah I didn't think the circulation settings should have anything to do with it either. The AC buttons works too. the weirdness only happens if you push hard on the circulation button. If I learn more I'll post back

 

btw, I don't get why the system would engage the clutch and then disengage immediately.. the service manual only has 3 troubleshooting situations:
1) condenser fan not running (it does, for a second)
2) clutch not engaging (it does, for a second)
3) AC not working

I guess I fall into situation 3

 

First use proper gauges to test refrigerant pressures.

If refrigerant pressures are fine, you might want to test the thermo switch (and also pressure switch) as described in the service manual.