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Old 03-06-2007, 12:22 PM   #1
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Join Date: Oct 2006
Posts: 20
Fuse for dash AC Georgetown MH

My problem: no AC in 1999 Georgetown M-265 motor home equipped with a 7.4L (454) Chevy drive train.

MY observations: The unit is as new, The AC compressor is labeled DELPHI, has not been bastardized. There is some pressure in the system, At this time I do not have PSI,

What happens: When AC is called for there is no power to the compressor. If max Air is called for the AC AUX fan on the front of the radiator does not operate. The blower fan does work in all modes and in the heat mode. When I toggle the AC switch I hear no sounds of relays.

My SWAG: Blown fuse, bad relay

My question: Where? I can not find the relay. I have tested all the fuses under the dash as OK, I can not find the relay associated with the Acc fan .

Thanks in advance for the help

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Old 03-06-2007, 09:13 PM   #2
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Location: Prairieville, Louisiana
Posts: 1,927

The first thing I'd do is to jump the two wires attached to the Low Pressure Switch(or pressure switch) which is mounted to the Accumulator Tank(also know as the Receiver-Dryer).

Purpose of the pressure switch:
The pressure switch senses internal pressures and can cycle the compressor off and back on based on minimum and maximum pressure limits. Pressure switches also turn on or off you condenser fan or Radiator Fan.

It is possible for the normal automotive A/C unit to leak up to 12 oz. of refrigerant per year. If by jumping the pressure switch, the A/C compressor clutch engages, the unit is most likely low of refrigerant, or the pressure switch is defective.

I have run across many defective low pressure switches.

In addition, the A/C relay is usually mounted in the engine bay, on the passenger side.

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Old 03-07-2007, 08:49 AM   #3
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Join Date: Oct 2006
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Thanks for the input, you are right on the money. I by passed the low pressure switch and got the AC to run, So I am off to have the system recharged.

Still havn't found the fuse for the AC system or the relay for the fan, but I'll have the guys at the shop point them out to me.

Again Thanks for the help.
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