2nd Gen Non-Engine/Transmission A/C quits blowing cold air during acceleration

[Dodoro]

It's pretty HOT here in Nashville TN, and I could use some help diagnosing my A/C problem. I understand that the system only cools the interior about 25 - 30 degrees from the outside temperature. Last week it was not cooling at all so I checked the low side pressure with one of those refill cans sold at the auto parts store, and it was about 25 psi. So following the directions carefully I added some to bring up the number. All was good until today 104 degrees outside and it felt like 110 in the truck. I checked the pressure and it was about 42 / 43 psi. It seems as if when I accelerate using more than a quarter of throttle it shuts off the compressor. No matter how quickly I get up to the posted speed limit the compressor won't blow cool/cold air for 3 or 4 minutes. Just enough time to feel miserable in the non AC cab.



I know the quicky fix cans of coolant is not the proper way to repair the AC, but what is causing this on and off again problem.



1. If I let out some freon will that stop the on and off issue ?



2. The radiator/inter cooler/condenser fins are clean. ( cleaned them 3 weeks ago and rinsed them out again tonight )



3. I do have that pesky oil leak between the power steering pump and vacuum pump problem ( didn't know it that would be related somehow )



4. I have 220,000 miles and all of the AC system is factory original.



5. I am on a tight budget as I own / operate a one man lawn care business and we are drying up fast around Middle Tenneessee so I won't have much money to throw at it until fall.



Thanks in advance

Dave D.



I can't think of anything else to provide you more info than that.

 

[HHhuntitall]

Is the clutch fan engaged when it gets hot? It has to help pull air through the condensor to help cool it. Also, if you overcharged the whole system, the compressor will build excessive head pressure quickly, making it turn on and off in rapid turn. Have you confirmed the clutch is spinning the compressor shaft and not slipping? Has the compressor gone the way of common sense in politics?

 

[Dodoro]

Thanks HHuntitall, yes the clutch fan is engaged when coolant temps are 200+ via the factory temp gauge. The compressor does not engage/disengage on the max setting. It stays engaged. Obviously with the engine running the pulley and clutch is turning, but I have no idea if it is slipping. My knowledge is pretty limited on the a/c system.



The last few days if I don't floor it, it seems to continue cooling. I have not noticed it intermittently turning off.



Any clues or, ideas ???

 

[MChrist]

I'm not much help here, but I remember on gassers, the a/c compressor would cut out on full throttle acceleration, then re-engage once you let off. But you say yours does it at 1/4 throttle?
Sorry, not much help.

 

[HHhuntitall]

At 220k, there are a lot of possibilities... ... You say you checked the pressure... was that with the truck running, A/C on high? That's where the pressue is most important. And it should stay close to 35, then come up when the compressor cycles off, then go back down somewhat slowly to 35, and then go cycle back off..... SHOULD... It sounds like the refrigant is low again, it's overcharged, or the compressor clutch is slipping. All are very likely, so I'd say watch the front of the compressor and make sure it is turning. Only the belt pulley should turn with the compressor off, leaving the front plate, which is the clutch assembly stationary. When engaged, the whole assembly should turn, and stay turning for at least 20-30 seconds, and at an idle, with that kind of mileage, it may stay turning for several minutes, even with proper charging..... Regardless, if it's turning, it should pull the refrigant level down a little from where it was with it disengaged, and that level should be AROUND 35psi... . The only proper way to charge it is by weight, but that's not where we are at this point... . The Dodge systems are pretty fogiving, but it needs to be somewhere in the neighborhood to even work half-way... ... take a look and let us know... .



As a side note, it is possible that you have too much refrigant in the system. That can effect it's operation, as well, especially if you somewhat overfilled it in mild weather, and now that it's hot, it's REALLY overfull..... R-134 typically is boiling and evaporating at an exponential rate at room temperature, if not under pressue... . it takes more pressure the higher the ambient temperature to keep it liquified... ... anyway, take a look and give me a few more details.....