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High Pressure Relief Valve

89chargedbird on Sun August 24, 2008 1:02 PM User is offline

Year: 1993
Make: Dodge Truck
Model: D-250
Engine Size: 5.9L Die
Refrigerant Type: R-12
Ambient Temp: 80.00
Country of Origin: United States

Hey all,
I charged and flushed this system about 1 1/2 years ago and the AC was working like a champ, nice cold air all the time. However, the other day I was at a stop light, the motor was at idle and then the High Pressure Relief Valve opened to let some of my expensive R-12 out. It didn't a few times and now I can see lots of bubbles in the accumulator window and the air is now warm.

Here is my question, what would cause this to happen? What is the high fail item? I am thinking about replacing the High Pressure Valve and the expansion block.

Any comments or questions will be greatly appreciated.

Thanks in Advance

mk378 on Sun August 24, 2008 1:33 PM User is offline

I suspect the condenser overheated because the fan clutch is about dead. You could add a HPCO switch if the system doesn't already have one.

GM Tech on Sun August 24, 2008 2:05 PM User is offline

At idle at a stop is the key-- condenser needs airflow- yours is lacking-- new clutch fan is needed or an operating electric auxilliary fan.

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

chris142 on Sun August 24, 2008 3:43 PM User is offline

I agree. Clean the bugs out of the condensor while you got the hood open.

89chargedbird on Sun August 24, 2008 7:54 PM User is offline

I replaced the clutch/fan about 2 years ago, what are some tips to make sure I need to replace it? How can you tell its bad, my motor water temp is normal.

mk378 on Sun August 24, 2008 11:19 PM User is offline

Was it a OEM fan clutch or a parts store knockoff? Recover, evacuate, and recharge to the specified weight of R-12. If the high side is too high, about the only thing that can cause that is inadequate condenser cooling. Usually the A/C performance will suffer long before the engine starts to overheat.

chris142 on Sun August 24, 2008 11:19 PM User is offline

With it running see if it's spinning fast enough to move any air. If you let it run at a fast idle with the radiator mostly covered it will get pretty warm the fan clutch should hook up and roar

89chargedbird on Mon August 25, 2008 8:57 AM User is offline

Purchased the clutch/fan from it could be bad..

What I did was charge the system with enough R-12 to make the bubbles go away in the accumulator window.

The high side went to 155 with the amb temp approx 78 with about 40% humidly

The system worked like it did before the high pressure valve opened up, I let the system work at idle for 30 minutes with no problems.

The fan is moving air because I can fell the air being drawn in from the front of the truck.

Could it be possible the a plastic bag or something was blocking the air and feel off before I got home?

At what pressure does the high pressure relief valve open?

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