Speaking of auto A/C 94 Caravan Compressor cycling

[BobReeves]

Easy one right, it's low on Freon! Wrong, it is full of R134 (over full at one time), the pressure switches (high side and low side) have been checked and double checked, even bypassed to test, the compressor relay is good, the vacuum lines and actuators have been vacuum tested but the darn thing still cycles the compressor just as if it were low on charge.

This is a 94 standard Caravan with the 3.3 engine (226,000 on the clock), no rear air or anything fancy. Bypassing the compressor relay will allow the compressor to run and it cools fine, also the radiator fan cycles along with the compressor so something is telling it to cycle but darned if my retired mechanic buddy and I can figure out what. Have a Hanes manual but it's all but worthless..

Anyone ever ran into anything like this?

 

[Soundguy]

Did you do a check on head pressure?

Soundguy

 

[orezok]

I had a similar problem and it was a partially blocked expansion valve.

 

[Bird]

Bob, be sure to let us know what you eventually find out that corrects it. How do you know it's full of freon? Sight glass? Or are you going by the head pressure? I'd be checking the head pressure first thing, as recommended by Soundguy, and if it's a partially blocked expansion valve, as mentioned by orezok, I'd expect that pressure to go up in a hurry. I think they've got the right diagnoses so I'll look forward to hearing whether it's correct or not.

 

[BobReeves]

We had gauges on it when we were doing the troubleshooting, don't remember the readings but when the compressor was running both hi and lo sides were close to normal. Seem to remember Tom saying something about the high side being a little high but not bad and bypassing the high side cut-out switch didn't make any difference..

Is there something else in the system that would make the compressor cycle if the expansion valve were blocked?

Thanks, this is more info that we were able to come up with..

 

[Soundguy]

If the exp valve was blocked.. I'd expect to see abnormally high pressures.. etc..

Soundguy

 

[orezok]

Read my message. It didn't say blocked, it said PARTIALLY blocked. It caused the head pressure to momemtarily rise until the high pressure switch opened and then the partially OPEN expansion valve bled off pressure until the high pressure reset resulting in a start stop situation.

 

[BobReeves]

Read my message. It didn't say blocked, it said PARTIALLY blocked. It caused the head pressure to momemtarily rise until the high pressure switch opened and then the partially OPEN expansion valve bled off pressure until the high pressure reset resulting in a start stop situation.

Understand but bypasing the high preasure switch on my van had no effect, it still cycles.

 

[Soundguy]

Blocked.. partially blocked.. either way it would be obviuos on a gauge.. that was the point of the message. If he's not seeing abnormal head pressures.. it's probably somewhere else..

Soundguy

Read my message. It didn't say blocked, it said PARTIALLY blocked. It caused the head pressure to momemtarily rise until the high pressure switch opened and then the partially OPEN expansion valve bled off pressure until the high pressure reset resulting in a start stop situation.

 

[tallyho8]

If the radiator fan is cycling on and off with the compressor, it is evident that it is not in the refrigerant system but in the electrical system. (sensors, computer etc)