Kind of an odd problem, and before I go tearing into things I thought i'd check here and make a post if I couldn't find any info on the subject. I asked around town a little bit but noone really had any definitive answers.

The Air Conditioning works for like 10 seconds, TOPS, sometimes less, then it starts blowing the hottest air possible. Even if I turn the A/C off it won't cool down at all and adjusting the temp. control does nothing. After the A/C quits working it quits for awhile, I haven't tested how long it takes to start working again but one of the times was ~a week in between trying.

I was talking to my dad and he said my grandparents van had the same problem and it ended up being some sort of control box mounted under the dash. Somehow it would get frozen (or something) when they tried to use the air conditioning and it would take like a week before it would start working again. He couldn't remember what it was called or what it did exactly, only that it was some sort of electronics mounted under the dash. I didn't think it would be the same problem because their van (while being a chrysler) is pretty loaded with creature comforts, mini-van style, and it was probably something to do with one of the crazy passenger temp control zones, but who knows.

Anyone else have this problem? or anyone able to point me in the right direction? I'd prefer to not have to pay a shop to figure out what's wrong, the dealership I got it from is willing to pay for the repair but I'm sure I'd get stuck with the diagnostics fee. Any help at all is appreciated!

 

Does the compressor disengage? It could be low on R134, which would cause it to kick on and then kick off when the pressure dropped below what the pressure switch says is the low limit. However, in this situation the pressure should come back up quickly and cause the compressor to cycle back on. The onnly instance I can think of when this would not happen is if the orifice tube was clogged, and the R134 could not get back to the low side. This could cause your situation, because the R134 would have to eaither seep through the orifice tube back to the low side, or bleed back through the compressor. Either of these would take the pressure a long time to come back up on the low side and keep the AC rom working because the low pressure switch says it shouldn't.
You really need to plug a set of gauges into it and watch the behavior of the compressor clutch. That will be very helpful in diagnosis.

Chris

 

Not sure about the 02's, but what it sounds like is whatever is controlling the temp door in the heater box is messing up. For it to go from cold to honest to goodness hot air means the door is going to its extreme.

If it were just lukewarm, ambient air temp air, I would think more along the lines of compressor, etc.

 

It definitly goes from ice cold to blistering hot, since it is cold for a second that lead me to believe it wasn't low on refrigerant.

Before I go searching later today about how much would a set of A/C gauges run me? I suppose I can stop by ricer-zone on my way home tonite and see if they have any for free-rental. If I can get my hands on a set i'll do a little more diagnosing and let you know what I come up with.

Thanks for the help guys,

James

 

Well I haven't had a chance to do anything, let alone get a set of gauges to check the pressure on the A/C system.

I thought i'd add one more thing that I just remembered earlier today though. It wasn't so much that the cold air didn't last very long, it seemed to work fine if I had it on the two lower settings. I never let it stay long enough on the lower settings and cranked it up to 3 and that's when it would always start blowing hot air. I haven't really been driving it at all lately but when I do i'm going to try it out again and see if I leave it on the lower blower settings if it will keep blowing cold air.

- James

 

Forget about the gauges.

Open the hood and put your hands on the refrigerant lines. The low pressure (big) line should be cold. If it is warm you might be low on refrigerant or the compressor has gone bad. If the line is cold you know the compressor is working fine and the problem is with the blend door (or control) in the cab.

 

Alright i'll check that later.

I took the truck to work tonite (a few blocks away) and on the way there the A/C was cold, and on the way to lunch it was cold as well. I just left it on the first notch both times and didn't try to make it push more air. When I get a chance to go on a longer trip i'll test this theory out again, then on the return trip try messing with the air speed controls.

 

Well the line was not ice cold but it was cool, but I don't think it's really an A/C problem anymore. Even lately with the cooler weather we've been having in the north if I turn the vents on it blows hot air, and only hot air. Doesn't matter where I set the temp it is still really hot. Im not sure why I was ever getting cool air in the first place but it certainly doesn't last long and without the A/C it won't blow cold air at all (unless the motor is cold)...

Anything else I should look into? I'm not familiar with hvac systems period so any help is appreciated.

- James

 

....this guy is the closest to your problem!

 

That or maybe the heater valve is stuck open causing hot coolant to circulate through the heater core all the time? If you think your HVAC controls might be bad I have a spare you can try.

 

No heater control valve on that truck....and the HVAC control is fine as it changes mode and temp ok at low fan speed.

 

I just went through this exact problem with my '98 Durango.

Empty out all the frean and put about 3 cans in it. Go to an AutoZone, or NAPA, wherever. be prepared to spend about $75. You need just a tool that hooks up to the low pressure side and shows you the pressure. It should have a port to screw in a freon can.

After you dump all the freon, or most of it (about 10psi in the system).

Turn the truck on and set the A/C to MAX re-circulate, and put the fan speed on high then keep adding freon. You should have about 40PSI on the low side at idle with the truck running and a/c on.


Merrick

 

I'm betting that if you remove the air door actuator you are going to find the adapter cracked... The actuator is trying to move the door, but with higher than "low" fan speed setting the airflow is actually pushing the door back. I still keep one in my tool box although I don't replace them as often as I used to.

 

Well at first I wasn't really 100% sure on all the specifics, and only thought it was an A/C problem. Now I think it's getting more obvious that it is not just a problem with the A/C and rather the HVAC system itself (somewhere). On low fan speed it still heats itself up to the warmest setting (or at least I hope that is the warmest setting, has me sweating bullets).

If I don't turn the A/C on it's always hot, but every now and then if I turn the A/C on it will briefly blow cold air. It doesn't matter if I leave it on low or high it does go back to blowing hot air again it just does it faster if I put it on a higher fan speed.

I think it probably is the blend door myself as well, it's just stuck on hot. Now if the issue is occuring at the temp controls or the motor itself that I don't know. How hard is it to get at this stuff? full dash removal? I don't have the time to properly diagnosis the problem let alone pull the whole dash .

Thanks for the help though, any more ideas keep'em coming! one of these weekends I'll probably be able to do some work on it.

- James

 

I think the A/C system uses vacuum actuated motors to open and close the doors. Either the door or the motor is malfunctioning.