For anyone who has been folowing my previous thread about the compressor clutch:
I finally got moms car in my shop tonight. Good news and bad news, the good news is the compressor seems fine and I wont have to mess with refrigeration lines. The bad news there is no electricity going to the compressor. I hate electrical problems. Where to start? I checked the simple things like the fuses and they seem ok. Tomorrow night Im planning on looking at all the underhood wiring to make sure the wires all look good. Other than that Im gonna need some good suggestions on what to do next. Theres a fuse box mounted to the passenger fender and theres a fuse and relay for the A/C. Both of these have power going to them. Im gonna trace the wires to see where they go since my Chilton book doesnt have this in their wiring diagram. As a last resort I suppose I could wire a toggle switch to the compressor but Id hate to become "one of those guys".

 

Try disconnecting the connector on the low pressure switch (on the drier) and jump the two pins in that connector together. If the compressor comes on then you probably need to replace the low pressure switch. You can replace the switch yourself without any freon lose, just unscrew it and screw the new one on, reconnect the wire and your good to go.

 

Gr8ride,
Heres what I found tonight. There isnt anything electrical going to the drier or the receiver. But there is a 3 pronged electrical switch on the pressure line near the receiver. I found one of the 3 prongs to have approx 5 volts and when I jumped it with one of the other prongs the radiator fan turned on. When I jumped the other prong nothing happened. Could this be the pressure switch you were thinking of? My next step is to get into the switch at the dash and see if its functioning properly. Everything else seems to be checking out.

Edit: Ok after lookin at my 99 F-150 I see the pressure switch on the air drier that you are talkin about plus the one on the pressure line simular to what I found on the Monte Carlo. My F-150 has the A/C parts out in the open and easy to access. It seems Chevy likes to hide things. There must be another switch somewhere on the Monte Carlo. I will look harder for it and probably tear into the dash switch any ways.

 

Oh yeah...Who da man? After rechecking all wires and fuses and looking into the control switch on the dash (which turned out to be a complex circuit board) I tried jumping the relay again. Apparently last time I tried that I wasnt making decent contact but this time the compressor kicked in. Now my next question, what kills relays? Do they die of old age or is it protecting a more serious problem?

 

Glad you found the problem.
I am use to playing with fords and older chevys, so I guess they have changed things up a little lol.
As for the relay, they really aren't designed to protect the system, they are just on off switches that handle more power. Relays do go bad, some times from a magnet that's become weak or from dirty contacts inside. Try cleaning the connections in the plug and on the relay really good and then see if it works, sometimes that's all it. If that doesn't work replace the relay and see what happens.

 

Bad news. I replaced the relay and the A/C still doesnt work. I also noticed, which I shoulda checked before, is the 2 slots in the control panel are always hot with and without the A/C on. Would it be ok to "permenately" jump the slots at the control box and do without the relay so the A/C is always on?

 

I dont think jumping the relay is gonna help. For one its hot all the time even when the car is off so I figure if the compressor clutch is constantly getting power its gonna just kill the battery. And second even when jumped and the compressor turning there isnt any freon circulating. There must be another valve or something controlling the system. I hate Chevy's!

 

So you are saying that with the relay jumped out and the compressor clutch engaged you are not getting any cold air from the vents? If that's the case then the system must be low on freon. Other than that I can't come up with anything. Tell your mom to buy a ford. lol

 

Yeah Ive tried to get her to buy a Ford but thats another story. Im takin it in tomorrow to get an alignment since I put new struts on it. Im gonna have them check out the A/C too. I will let you know what the outcome is.

 

Ok update:
After takin moms car to the alignment shop I was almost spot on with the struts. They made one slight adjustment at one tire to get it within tolerance. The A/C...thats another story! Im no A/C expert and info on the subject is hard to come by. Also it seems the techs at the shop I went to are in the same boat as me. Of course I didnt get to talk to an actual tech but I got friendly with the guy at the counter who got that job because he thinks he knows it all. Any way I wanted to know why the compressor doesnt come on...simple question right? Well the tech went straight into lookin for leaks and whatnot. He bypassed all the the other stuff and got the compressor to run to locate the leaks. OK now I pretty much did all that to begin with except leaks were the least of my concerns. Basically from what the guy at the counter told me was there is a little resistor that I wired incorrectly and that was causing fuses to burn out. WTF? I never once had a fuse problem and now the tech is poppin fuses? Ok these guys have less of a clue than me. After spending 70 bucks for a diagnostic test and whatnot I would think they could tell me something useful. But no they want to do all this and that and charge me 275 just to get to the point where there are no leaks and the system holds freon. This still doesnt fix the problem with the compressor not receiving any voltage to engage the clutch. So to make a really long story shorter its cheaper to replace every part in the system than it is to take it to a so called expert. I refuse to let this chevy kick my az. Im gonna fix it one way or another and not spend a fortune! Im open for suggestions. Tomorrow I plan on goin to the gm dealer and gettin this magic resistor thing and also gettin a high side pressure switch that I think does double duty as an air drier/pressure switch.

 

Case closed on the compressor issue. Lack of freon in the system means there isnt enough pressure to turn the compressor on. Good thing I figured this out before I bought a new one.