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1994 Sentra compressor going bad?

aliaZ on Sun August 17, 2008 8:25 PM User is offline

Year: 1994
Make: Nissan
Model: Sentra
Refrigerant Type: 134
Ambient Temp: 86
Pressure Low: 80
Pressure High: 175

The AC is not cooling very well. Do the pressure readings indicate a weak compressor? Or is the expansion valve stuck open? If the 134 level was low, I'd expect the low side to be 20-30. The condenser looks reasonably clean, and both fans are blowing pretty hard. The car has 204k miles on it, the AC has never been touched.


TRB on Mon August 18, 2008 1:09 PM User is offlineView users profile

Looks more like it is low on refrigerant and the clutch is not engaged. Some extra data would probably help determine what's going on. Like current refrigerant level?


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aliaZ on Mon August 18, 2008 1:28 PM User is offline

The clutch was engaged, and wasn't that makes me think the refrigerant level isn't the problem.

I don't know the amount of refrigerant in the system, but I could evacuate and recharge with the proper amount to be sure. She had taken it to a shop before I got my hands on it, and they told her the refrigerant level was fine. They thought maybe the compressor was worn out. This wasn't a dedicated AC was Kwik Kar, so I have some doubts about their level of expertise.

If the TXV was stuck open, would it cause the high side to be too low, and the low side to be too high?


aliaZ on Mon August 25, 2008 11:50 AM User is offline

OK...this weekend I evacuated the system and fully charged it, with no change.

High side is 175, Low side is 80, but drops to 60 if I rev the engine. Spraying the condenser with water made no difference in pressure. I notice that when I shut the AC system off, the High and Low side equalize within 3 or 4 seconds. The suction line is warm.

Any ideas?


mk378 on Mon August 25, 2008 2:51 PM User is offline

Try turning down or killing the evaporator fan (unplug it so you can leave the switch on and engage the compressor). That should make the TXV close down and lower the low side. If it doesn't budge, could be a stuck TXV. Could be a bad compressor either way.

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