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Old 11-08-2006, 01:10 PM
sixto's Avatar
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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?

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Old 11-08-2006, 01:22 PM
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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

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Old 11-08-2006, 01:24 PM
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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.

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Old 11-08-2006, 01:54 PM
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smoke gets in your eyes
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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.

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Old 11-08-2006, 02:22 PM
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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.

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Old 11-08-2006, 02:51 PM
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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.
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Old 11-09-2006, 11:27 PM
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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.

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Old 11-09-2006, 11:45 PM
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as stated above its normal. "pressure equalization"
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Old 11-11-2006, 06:38 PM
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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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