Pontiac Repair: intermittent A/C 2003 pontiac montana, pontiac montana, car parts stores

Question
QUESTION: The A/C on my montana is intermittent. I have a good Charge, have bypassed the clutch relay (clutch engages when relay jumped). What wiring or sensors should I check? I see a pressure switch under the air cleaner and some wires going to the rear of the compressor. what else can I look for? When the A/C works, it works well.

ANSWER: Hi John:

well My first guess would be the pressure sensor on the Hi side line that has 3 wires on it. If that sensor is bad and sending the wrong pressure reading to the ECM it will inhibit a/c clutch opertaion. That is my first guess. If it wuns when you jump the relay the cut out swaitch on the back of the compresser is good. that is a hi pressure limit switch/cutout switch. Does this have any service engine soon lamp on? If so some DTC's will inhibit compressor opertaion as well. Idealy you need a scan tool so you can see what the pressure switch in the line is reading if the reading is correct then you could possably have a bad ecm that is not allowing the relay to turn on or a wining issue between the relay and the ECM. These vans had wire harness rub thru issue at the radaiator core support on the lft side of the van take a look at the harness and see if it's pinched or rubbed through right by the rdatiator attachment bracket on the top.
Good luck :)


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

QUESTION: I located the trouble near the pressure sensor. The 5v reference wire was damaged. My next question is, what scan tool can I use to check the values on the A/C system. I checked the local parts store and they stocked actron code readers, but they only appear to read engine codes. I appreciate the help!

Answer
You need a full bloan scan tool which are expensive! code readers will not do what you want. You can do a google/ebay search and find inexpensive scan tools that will work with a laptop/net book computer those are around $200.00 or so and they will do what you want. some of the BIG BOX car parts stores have tool rentals they may rent scan tools call around and see what they have to offer. You need one that will work on a OBD II computer system which is 1996 and newer car/truck.