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high side pressure 450 and going up

paradiddle1 on Tue April 12, 2011 7:26 PM User is offline

Year: 1997
Make: Dodge
Model: Caravan
Engine Size: 3.8
Refrigerant Type: 134a
Ambient Temp: 85
Pressure Low: 60
Pressure High: 450
Country of Origin: United States

I am having problems and checked ac pressure from cold start at 85 deg ambient. I am getting over 450 on high side and climbing after 1 min and engine not up to temp yet.

I replaced compressor and drier about 2 months ago. Flushed Vacuumed and refilled to proper weight and had nice pressures of 245/40 with 45 deg out the vent.

I think something must be clogged down stream. I did not change the expansion valve. What can cause that over pressure?

GM Tech on Tue April 12, 2011 8:22 PM User is offline

So what is the cooling fan doing? Should be on at or above 175 psi....

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......

paradiddle1 on Tue April 12, 2011 11:06 PM User is offline

never mind - Its that damn rad fan relay that wouldn't come on. It brought the numbers back down to previous. Those Mopar electronic rad fan relays are junk and I have replaced 3 already. It also maybe because they are aftermarket. I had even replaced the computer thinking that it couldn't be 3 relays. The relay comes on at depending upon many factors and I can follow them by checking voltage from 5V temp sensor. It usually kicks on without ac at 2.0 volts and cuts out at 2.2. With AC on it forces the fans on unless the 5v temp is too high like 2.4 volts. Someone gave me a chart once on volt - temp. ex: 2.0 volts = 225 deg. 2.2 = 200 deg. But I'm guessing without digging thru my files.

Edited: Tue April 12, 2011 at 11:12 PM by paradiddle1

JACK ADAMS on Wed April 13, 2011 12:05 PM User is offline

Chrysler has had a problem with those fans drawing to may amps and melting the plugs to the fans. Check your pigtail just to make sure. Good luck.

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