A/C problems - complicated

I'll try to make a long story short. 1998 GTP with dual climate controls. Had a new A/C compressor installed in June this year, the old one was leaking. At the same time a new accumulator and orifice tube were installed and the rest of the system flushed. All was well for about 2 months when the A/C would intermittently blow hot air and a few minutes later begin working like nothing was ever wrong. I returned the car to the guy who did the work and he was stumped but was working on it as he had new ideas but the law stepped in and he is no longer a free man so I got my car back but now A/C doesn't work at all. The compressor clutch never engages. The A/C relay is good but not getting a signal to activate the clutch. If I jumper out the relay the A/C will work for a few minutes but them start blowing hot air. At the time it blows hot air I felt the line to the evaporator and it was HOT. Today I just put my gauges on the A/C and the low side started out at around 35 psi and the high side at around 175 psi. After about a minute of running the low side was down to 25 psi and the high side was reaching 275 psi and climbing when an o-ring blew out on my gauge set. I shut everything off there. I'm guessing something is plugged, orifice tube? The A/C compressor not coming on is a separate issue I think. Anybody have an idea what is going on? I am no A/C expert.

What was the actual ambient temperature when you ran the gauges on the low and high sides?

The 25 low and 275 is definitely abnormal and off the ABCD charts. Orifice is a possibility but you might consider adding more R134a refrigerant. Due to the low charge the A/C compressor may not engage or cycle properly. The PCM uses the lo/hi pressure switch for compressor turn on via the A/C relay. That switch is located by the accumulator.

thanks for the reply. I'll try putting some more refrigerant in and see if the compressor comes on then. I have a question, how much pressure is required for the compressor clutch to engage? I started out at 70 psi low side before I forced the clutch to engage. Any idea what the cut out setpoints are for the low and high pressure switches? thanks again.

Is the radiator cooling fan coming on when the AC is on? If not, that would make the high side run excessively high.

Is the radiator cooling fan coming on when the AC is on? If not, that would make the high side run excessively high.

That an interesting suggestion but confusing to me. Refrigerant pressure is what governs fan turn on. See below.


There are three basic modes for the fans (total two): OFF, Low-Speed, and High-Speed. These modes are controlled by the Powertrain Control Module (PCM).

Fans OFF:

* When the coolant temperature is less than about 220°F (104°C) or
* The A/C refrigerant pressure is less than 190 psi (A/C off).

Low-Speed:

* When the coolant temperature is between about 220°F (104°C) and 230°F (110°C) or
* The A/C refrigerant pressure is more than 190 psi (1310 kPa) or
* When car is turned off and the coolant temp is more than about 284°F (140°C) and system voltage is more than 12 Volts. Fans will run for about 3 minutes.

High-Speed:

* When the coolant temperature is above about 230°F (110°C) or
* The A/C refrigerant pressure is more than 240 psi (1655 kPa) or
* When certain DTCs are set.

What I meant by this was:

If for some reason the cooling fans were not coming on, the high-side pressure would rise rapidly and become too high. The AC performance could be diminished as a result.

The condensor is where the refrigerant reverts back to a liquid as it is cooled. If the condensor is blocked by dirt or bugs, if the radiator is too hot, or if the condensor cooling fans don't come on, the heat will not be properly removed from the refrigerant. (I'm speaking generically, of course).