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Questions and Answers

Cadillac Deville A/C Doesn't Work

Q. Dear Sir, I have a 1994 Cadillac Deville 4.9 liter V-8 engine. My problem is this, I have changed my A/C unit, replaced the evaporator, expansion valve and receiver dryer and took it in to recharge the system with 134A. The blower comes on but blows hot air. The problem is that I'm not getting any power to A/C unit to have the clutch engage.

Cadillac Deville A/C Doesn't Work

I check the relay switch and the fuses current is going through those areas but not to the line that runs to A/C clutch unit. Your help in this matter is greatly appreciated.

Eddie

A. Power for the A/C compressor clutch comes directly from fuse B7 (10 amp) in the under hood fuse box. The A/C relay turns that power on and off and is powered by fuse A3 (10 amp) in the under hood fuse box. Power from the fuse goes through the A/C Low Pressure Switch, to the A/C High Pressure Switch, to the A/C relay and then to the PCM.

The PCM decides when to turn the A/C on or off based on various inputs such as throttle position and electrical load.

You can check fuse B7 and the orange wire from the fuse to the A/C relay and the dark green wire from the relay to the A/C compressor clutch.

Then you can check fuse A3 and the pink wire from the fuse to the A/C low Pressure Switch and the dark green wire from the A/C Low Pressure Switch to the A/C High Pressure Switch. Check the dark blue wire from the A/C High Pressure Switch to the A/C relay. From there the dark green/orange wire to the PCM.

If you ground the dark green/orange at the A/C relay and the A/C compressor clutch kicks on, then the problem may be in the PCM or one of it's inputs. If it doesn't, then you know for sure the problem is in the circuits I mentioned.

I don't know if you have manual A/C or Automatic Climate Control so this is the best I can do for you at this point.

Additional Information provided courtesy of ALLDATA

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