1995 Buick Riviera A/C

[GMC Man]

1995 Buick Riviera 3800 vin K. NO check engine light .A/c compressor pulley broke and also burned the coil. I have replaced the clutch assy including the coil and now I don't have power to the coil circuit. I checked for power at the pressure switch and none there also. There are no blown fuses.I checked 3 locations. Also now the engine cooling fans don't come on low speed. Only when the engine gets hotter than the normal temp, according to the gauge, then they run high speed. I was holding the throttle at about 3500rpm's to warm the engine and it would drop rpm's to about 2000, back and forth like the ecm were limiting the rpm. I had a similar experience 3 or 4 years ago and then the relay and plug had gotten hot and I had to replace them, but now no sign of heat there. Does anyone have a suggestion??

[Gus]

Looking at a schematic for a '98 Riv, there are three wires to the pressure sensor......the middle wire(grey) to the "B" terminal should have 5.0 volts......you can NOT jump this sensor to make the compressor engage.....

If there is a request from the HVAC, for A/C, to the PCM and there is enough pressure in the system, then the PCM grounds the compressor relay, providing power to the compressor....

[GMC Man]

Gus,
 The pressure switch I checked for voltage was a red one with 2 wires located on the back of the compressor. 0 volts to ground on either wire.  Where is the one you describe located?

[GMC Man]

Gus,
 Also my experience with this car is that '95 is unique to itself. '96 to '98 have a great deal of commonality, but '95 is different. Some OBD I some OBD II.

[Gus]

Unfortunately, I don't have a schemaatic for a '96......It's possible you may have the old system without the pressure sensor, the one that has  a pressure cyling switch on the accumulator(CCOT)....if so, check for power there....If you have power there, and you have good system pressure, jumper the harness and see if the compressor runs.....otherwise, we need a schematic...

Have you checked for codes? There are codes that will disable the compressor....

Have you checked the system pressure with gages? Should be equal to or greater than ambient temp, on a cold engine...

[GMC Man]

  Gus I have 13.5 volts at the sw. in the refrig. line and when I unplug it from the sw. ,the engine cooling fans came on. Engine running-a/c controls on.
  Which switch is the low press and which one is the high? It seems that if I open a control circuit that the fans shouln't come on. Am I incorrect to assume that the same control wire powers the clutch and the cooling fan relays?
  If I had a wiring diagram I could trace the circuit.
  I don't have a set of gauges, when it comes to that part of a/c I hire that out. All was working perfectly before the clutch broke while I was driving the car using the a/c. No Check engine lights.  No sudden release of refrigerant.  The pulley simply broke at the point that the face welds to the actual pulley.This burned the coil and there was no electrical continuity. I replaced the entire clutch assy.

[Jim Fairbanks]

Hey Gus...I don't know a lot about AC, but I can give you some diagrams....Jim

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[GMC Man]

Fixed. The refrigerant was low. I repressurized the system with refrig. and all is well now.

[JackC]

As my wife always says, check the simple stuff first.  She says that I think too much and look for difficult stuff before simple stuff. At 76 years old, I am still trying to learn.