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High side problems

xcrunner0 on Sun May 31, 2009 11:52 PM User is offline

Year: 2003
Make: Nissan
Model: Xterra
Engine Size: 3.3
Refrigerant Type: 134a
Ambient Temp: 75
Pressure Low: 55
Pressure High: 400
Country of Origin: United States

Hey guys I could use some help on this one.
Here's the situation. The compressor is cycling on and off at what appears to be a high side cut off. I believe it is a restriction or clog in the O tube but I wanted to get some second opinions. When the a/c is engaged the system runs at about 41 low and 175 High with the vent discharge at 49deg and the evaporator line temp at 40.2 degs. It will hold like this for about 5 minutes until the high side slowly starts to climb, and then rapidly moves to around 400psi and the vent temp increasing to 56deg at which point the compressor starts to cycle. This process takes about 10 minutes. The cycling is about 5sec on 5 off. So I started by cleaning the condenser real well, which did not appear to have any effect. I also hosed down the condenser when the pressure increased, which did not appear to decrease the pressure at all. So this is making me think its not an airflow problem but a restriction. I wanted to know what you guys thought and if I was on the right path, and if anyone's had any experience with this vehicle/ engine.
Thanks in advance.
Alan

TRB on Mon June 01, 2009 10:25 AM User is offlineView users profile

If you know the refrigerant level is correct I would check for cold spots in the condenser. This is a classic case of over charge, air flow or condenser issue. Both low and high side readings are high for this vehicle.

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xcrunner0 on Mon June 01, 2009 6:24 PM User is offline

Yes it does seem high, whats your take on the slow increase in pressure from 41 L and 175 H to 55 L and 400 H? I don't have a whole lot of experience on what that is characteristic of. Wouldn't the air flow and condenser issues be ruled out with the water test. Even if part of the condenser was blocked wouldn't you see some drop in pressure when water was applied?
Correct me if I'm wrong but will a blockage in a metering devise appear as high high side and a low lowside, since the refrigerant cannot move?
Thanks for the help.

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