GMC Repair: Air Conditioning, pressure switch, freon

Question
QUESTION: I have a 1995 6.5 turbo diesel... the air conditioning will not work.. have checked the freon and it is good... just will not get cold in the cab...

ANSWER: Hi
Is the compressor running? Does it turn on when the switch is depressed?
Is the Fan inside the cab running at all speeds?
If all these are OK, you need to have the freon level checked AGAIN.
If not on the inside fan, that system will need to be diagnosed.
If the inside fan is running, and the compressor IS NOT, there is a low side pressure switch mounted on the Accumulator, it COULD be at fault.
There is also a High side pressure switch located on the Compressor.
The clutch may be at fault.
Please follow post back.
Thanks
Pawl

---------- FOLLOW-UP ----------

QUESTION: Pawl, thanks for getting back to me... I think it is one of the switches how do I know witch one???

Answer
Hi Charles,
jump the two wires together, using a very small wire.
I would start with the low pressure switch, the one located on the side of the accumulator.
If you need to replace this one, evacuation and recharge of freon will NOT be necessary.
If it ends up being the one on the compressor, evacuation and recharge of freon WILL be necessary.
I will also tell you, I have only replaced 2 high side switches (the on on the compressor)BECAUSE of a bad switch,  in ALL my years of working on cars.
I hope this helps.
Pawl