1996 Cadillac Deville Need some direction

Tiny
TRISTAN846
  • MEMBER
  • 1996 CADILLAC DEVILLE
  • V8
  • FWD
  • AUTOMATIC
  • 120,000 MILES
My brother and law has asked me to look at his Cadillac the A/C is not working. I do refrigeration in supermarkets, I do not usually work on cars. I could use some direction. This is what I have found so far.
On the dash the A/C controller will switch from heat to cool, but when you try to switch from Econ to Auto it will not. It always goes right back to ECON?

The system with nothing running static pressure is 120psi suc, and head, so I know we have some kind of charge in the system.

The LPS, and the HPS switches are all closed, but there are two other switches, they are on the liquid line, and it looks as if they are seperated by a metering device. I do not know why they are their, and I only have 4.9vdc coming to these switches when I unplug them and test.

Under the car on the compressor I do not have any power coming to the clutch.

I am not use to working on car units, and do not know if their is a control I missed to check, I find it odd the unit is stuck on the econ, becuase if it is like supermarkets we would be pulling outside air in and we would actually need automatic A/C on a hot pull down.

I would appreciate any direction. Thanks Tristan.
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Friday, July 3rd, 2009 AT 1:41 PM

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Tiny
FACTORYJACK
  • EXPERT
The two components in the liquid line are temperature sensors, they are 5-volt sensors, and yes there is an orifice tube in between them.

The fact that it is defaulting to econ, is a result of potentially false low refrigerant detection. The reason I say potentially, is a faulty switch or sensor can make the system think it is low, when actually it is not. You said static pressure was 120, at what ambient(outside) temperature were you at. If you were in warm ambient, the pressure could be that high in a low system.

Do this, press 'off' and 'warmer' together on the climate panel with key on until all the segments light and release. You just entered diagnostics and codes should display, you are concerned with ACM codes.

You can have two possible codes, a low and a very low. Not sure, but I think b1347/b1348 are the codes. If you push fan down, the dic should read 'PCM?'. Scroll with fan down until you reach 'ACM?' (Or ACP) and push fan up. You will open the ACM possibilities to read data, clear codes, etc. Display clear codes, after you've read and recorded them, and push fan up. Codes cleared, cycle key, and you should have compressor operation, at least for a short time.

With manifold gauges installed, watch your low side pressure, and cycle time. If the pressure drops rather rapidly, and the compressor cycles rapidly, it is low on refrigerant.
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Saturday, July 4th, 2009 AT 5:40 PM

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