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sixto 11-08-2006 01:10 PM

Caravan AC hisses when compressor disengages
97 Grand Caravan with front and rear AC - recently there's 5-10 seconds of hissing from the front and rear evaporators when the AC compressor disengages. Seems to work fine otherwise. What does this mean?

93 300SD

Nate 11-08-2006 01:22 PM

the switch is going out... they're all like that, i think...

no ideas on how to prevent it, other then with limited use. no ideas on replacement either


dkveuro 11-08-2006 01:24 PM

Equalization ...quite normal...although manufacturers try to reduce the problem...the orifice/expansion valve has a small hole and the hi side and lo side are balancing out.


sixto 11-08-2006 01:54 PM

Thanks for the replies.

Switch = could be the vaccum actuators but why would there be a corresponding sound from the rear evaporator area?

Expansion valves = you're saying it's not pending failure? It would be too much of a coincidence that both expansion valves degrade at the same time.

93 300SD

pwogaman 11-08-2006 02:22 PM

My 1996 was doing the same thing prior to my servicing it. I went through the troubles detailed in this thread:

After replacing the expansion valves and the properly charging the refrigerant the problem was gone. I suspect you are getting low on refrigerant or your expansion valve is not closing tightly enough.

gmercoleza 11-08-2006 02:51 PM

The TXV hiss is "normal" however oftentimes a low charge condition will cause it to be more pronounced. You might want to check your charge.

sailor15015 11-09-2006 11:27 PM

My mom has a '99(I think) Town & Country, which is essentially the same vehicle, and hers started to hiss and a few weeks later she complained of it not getting cold enough. I put my gauges on it and I think I remember adding at least 2 twelve ounce cans in there and all was good with no more hissing. I'd check the charge.

kmaysob 11-09-2006 11:45 PM

as stated above its normal. "pressure equalization"

OMEGAMAN 11-11-2006 06:38 PM

Expansion valves never close off completely. There is always some type of small bypass hole to allow refrigerant to continue to flow because it carries the oil for the compressor.

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