'84 GSL with converted 134a A/C. The compressor's been replaced within the last few years, but here's the problem.

It's fully charged (it's got plenty of 134a in it) and was blowing nice and cool yesterday morning. It took me about 45 minutes to get to my destination. All the while, the A/C was working just fine. I'm at my destination for, oh, 3-4 hours (maybe a little more) and when I leave, no A/C/. The clutch on the compressor would not come on. I pull over, make sure it's not seized up, check all the connections, fuse, etc, and I get nothin' but a bunch of hot air. I kill the car several times trying to "reset" it (yeah, I'm a computer guy by trade) hoping that might resolve the problem... nothin'.... So, I get to my 2nd destination, leave the car for another 3-4 hours (checking it around the 2 hour mark and it still wasn't working)... but when I left around the 4 hour mark, it worked immediately and started blowing cold again!
What gives?!?!?

This is the 2nd time it's done this to me, although last time, after I just started to go ahead and take off, it started working then... but this time, I don't know what it was.

Any ideas on what I should check? -- Oh -- and by the way... it's worked all morning on my almost 1 hour trek to work too. (now you see why I titled this thread "Tempermental" A/C problem)

Thanks in advance,

Jeff

 

Guess most people don't know anything about the A/C system? If you do, please throw in your 2cents worth!

 

Faulty AC relay mabey?

 

Mine does the same thing dude.

 

Here's another thing I have noticed.... if I'm driving down the road sometimes it will go out just for no reason and sometimes I can shift into neutral, floor it into redline, and it might come back... coincidence perhaps?

Also, might it do this if the system is overcharged?

 

Some things to try.

Do you have a DVM? Test Light?

When it stops working check the line going to the compressor for +12. This will let us know if it is Electric or the compressor. And we can go from there.

 

Maybe the AC just doesn't like hot weather?

Seriously, when it's a problem like this, it's pretty much gauranteed to be electrical.. I like the relay suggest, as Many relays will act that way when they're on their way out...

 

Dodge place thought the Same thing on My Dakota, PCM and 5 days of work later, they still had not found the problem. It had to large an air gap between the Pulley and the clutch, I spent 10 minutes trouble shooting the system and took out one Shim and fixed the problem.

 

Yes, an overcharged system could behave this way, except for the part about taking hours before you could use the AC again.

Do you have an electric fan or belt driven? Reving the engine with a belt driven fan will increase the air flow through the condenser, which is the radiator looking thing that is in front of the radiator. Increasing the air flow will remove more heat, and lower the high side pressure. This symptom is an indication that the high side pressure may be getting too high. I don't remember if there is a high pressure cut off switch, but I think there is.

Another important part is it took several hours before you could restart the AC. If the problem was only a cooling issue, the pressure would drop soon after the compressor shut down. Your system would cycle on and off. Maybe run a few seconds, and then shutdown for a few minutes. Even an overcharged system would cycle over a period of minutes, not hours. This symptom and the above point to a restriction, such as a stuck expansion valve. A faulty high side switch could be the problem too.

Does the behavior have anything to do with time of day/outside temperature? Higher outside temp means higher ac system pressure. You can put a box fan in front of the car while it is idling and increase air flow through the condensor. You can also spray some water on the condensor and drop the pressure, but its a bit messy.

Get your wiring diagram out, and either a volt/ohmeter, or a test light. Familiarize yourself with where stuff is, specifically the switches on the freon lines. You'll find them on the passenger side, just before the freon lines go in and out of the firewall. Then you can use the test light to determine what is turning the compressor off. Do some testing while things are working, and when they aren't, and compare results.

I think you can do a lot of testing with the key on, but engine off. With the engine off you can safely use a jumper to jumper out the pressure switch, and see if power is getting to the compressor. Don't do this with the engine running, or you may damage the compressor.

A set of gauges is a good investment too. Even an inexpensive gauge would be useful. You want to see if the pressure is truly high.

If the compressor was actually locked up, you would have heard a belt squeal, and really bogged the engine down. I recently replaced a locked up compressor on my wife's Windstar. On a coworker's Blazer, a seized AC compressor bogged the engine down to the point the engine stalled out.

And spend a little time on the ground in front of the car. Are there any restrictions to airflow through the condensor? Are a bunch of the fins bent? Straighten them out, spray some water through to clean things up. This can't hurt, but the part about taking several hours to run again kind of rules this out.

Hope this helps.

 

Oops: I may have steered you wrong on the location of the high pressure switch. I just looked at both of my cars. On my '82 GSL it is under the hood, on the passenger side, on the smaller freon line. On my '85 it must be under the dash, probably inside the plastic housing for the evaporator. Since yours is an '84, its probably like my '85. The AC relay should be under the hood on the driver side. The pressure switches interrupt the path to ground for the relay control coil.

 

WOW! That's a LOT of useful information... It's greatly apprecaited too! I'll see what I can find out.

As for it possibly being overcharged, I bought a can of that oil/seal-fixer-upper/134a stuff (again, because mine's converted) and it had a guage on it... I read it wrong when I put the stuff in and it showed that the reading was ON the line between the yellow (danger) and the red (pressure too high) marks.

Should I let some of it out? or do I have to "capture" it like you do the old freon (or like you're supposed to do.)

 

Before you let any out, see what the pressure shows on the gauge, especially the high side. Check an air conditioning type site and print out a pressure chart. If you are consistently too high, then you need to let some out.

If you "accidentally" let some out, try and do it slowly. You don't want to loose much (actually any) of the compressor oil. I've learned to error towards a slightly low charge rather than high. An overcharge can reduce system efficiency anywhere from 20% to 40%.

I use a digital indoor/outdoor thermometer as part of my AC test equipment. I stick the outdoor probe in the vent so I can see the air temp. After the interior has cooled down, I put the air on recirc, at low speed. As long as my air temp is consistently in the high 30's to low 40's, I leave it alone. If it dips below 32, then its time to add a little refrigerant. And if it is in the 60's or higher, its probably time to add a lot of refrigerant. I keep one with hi/lo memory in my wife's Windstar. That way I have an idea that the AC needs checking before she notices a problem.

 

I haven't yet tested the voltage on the switch yet, but the temp typically is in the 45-50 degree range depending on outside temp and engine RPM's.... But I have noticed that it's considerably worse in the afternoons, and typically it's hotter in the afternoons (which, of course, is when I need it most!)

 

I say you pull the whole damn air conditioning out of the car and reap the benefits of the weight and horsepower it was taking up. Then you can roll down your windows and make your own a/c :P.

 

Thought about it, and maybe if I lived up in WA, but down here in Texas, it's hotternhell most of the year.... !!!

 

On my 85 GS the high pressure switch was under the metal plate in front of the radiator mounted to the reciever/drier. There is a large rubber plug on the drivers side that you can pop off and view the sight glass. You should be able to see the switch and wiring from there. I just got done replacing my hoses and charged my system last week.

 

I also forgot to ask... where is the A/C relay so I can check it?

Thanks!

 

You need to trace back the power for the comp clutch. Depending on the model and options you may have one of 2 different systems installed in these cars. If you have power steering youll have an extra relay that cuts juice to the comp when the p/s unit operates (I dunno why). If you dont have ps, then that relay plug has a white cap on it which contains a jumper across 2 terminals. This relay and the A/C comp relay are on the drivers side of the engine compartment aft of the strut tower. You may just have a bad/ intermittent connection.

 

Did you find the problem?

 

Does anyone here go through the trouble of removing the whole A/C system and putting it back together each year for the summer time?

Also, why am I noticing cold 'smoke' coming from the vent when the A/C is on? It looks like condensation, but I've never seen it in any other car.

 

Zactly what it is...condensation when it's pretty humid out. I get it in my other cars as well.

 

Actually, I think I did.... I think it was a combination of engine bay heat and backed up heat from a clogged cat. I gutted the CatCon so now I just have the shell there (and a sh|tload of power back after doing that and removing the smog pump belt) and my engine temp NEVER gets above the 1/3rd mark and the compressor never shuts off for long periods of time anymore (it cycles like normal though).

So, the moral to the story is, when your A/C doesn't work, gut your cat! (no, not really).

 

Good to hear that you *may have* found the problem. I've been following this thread since the beginning, if only because 3 weeks ago I recharged my A/C system and it's blowing very cold right now.

Incidentally, about a week ago, I left work for lunch out and it blew cold the whole way (110d F day here), and on the way back, would not blow cold at all. Fan was working 100%, A/C lights inside looked good (compressor light), and the belt and compressor seemed fine, but the compressor clutch wasn't turning.

Turns out that the relay that controls the A/C clutch is located just under the driver's side hood corner near the windshield and is a 'double-wide' relay - this was stuck open and wouldn't engage the A/C compressor clutch, therefore, without the compressor turning, no high/low pressure differential, no cold air.

A quick 'thump' to the relay cleared the contacts and it started working again just fine.

Something to think about that may or may not be a factor in your case. HTH,