Mechanics

NO AC LIGHT COMPRESSOR NOT ENGAGING

1997 Chevrolet Suburban • 175,000 miles

I am trying to get my 97 K1500 Suburban AC working. When I purchased the truck, I new that the AC did not work. The previous owner told me that the compressor locked up, so he changed to the shorter belt and moved on. Now that I've moved to FL, I need the AC. While changing out everything I found that the rear ac has been disconnected and the shared pressure hose obviously changed out. I bought all new parts (accumulator, compressor, condensor, low pressure switch, high pressure switch and orafice tube filter). I'm not gonna worry about the rear air, I'll just be happy to have the front ac working at this point. Now that I have everything installed on the truck, I vacuumed out the system and it holds. The problem that I'm having is that my dash light is not coming on and the compressor is not engaging. I checked and I have no power at the low pressure switch. Checked all fuses and relays, everything is good. I'm not sure where to go next. I've read several things about checking the control head in the dash, which I may try next. This may also be relavent, the 1st and 3rd settings don't work on my fan settings.
AD
Avatar
Czr1760
July 28, 2012.




So they just ran a hose for a vechile without a rear air to bypass the rear air?Also how much charge did you put in the system?

Saturntech9
Jul 28, 2012.
Yes. They just removed the original hose that split and installed one for the front only. I only installed a partial can before stopping for the night. If I were filling front and rear ac, the system is supposed to hold almost 5 lbs of freon and 11oz of oil. Since I'm only charging the front, I figure my charge should be much lower. Freon isn't cheap and once I started to get some low side pressure to rise I stopped because the compressor didn't engage. If the compressor doesn't kick on, my low side pressure is just going to spike up. That's when I checked the low side switch and found that I have no power to the switch.
AD

Tiny
Czr1760
Jul 28, 2012.
Ok, let me write this again, since I did once, made a donation and my reply was gone. I "upgraded" with the donation this time, so hopefully this will work. Swapped out lights, so now the ac light on the dash works. Jumped the ac relay and was able to have compressor cycle. Tried filling the system, but the ac switch in the back of the compressor blew out. Now I'm starting all over again. Have to vac out the system. I read about a transistor on the control head that I could replace, but it has a differnt number than listed on the internet. Should I try this or just go to the bone yard and find another control head, but nothing saying that one from the yard will work anyway. Please help, I've made two donations to this question now. Have spent way too much time and energy already. I'm guessing that these problems were always present and the previous owner knew about all of them and just didn't tell me.

Tiny
Czr1760
Jul 28, 2012.
Iam going to be asking you alot of questions so did you replace both hoses to the rear evap core to bypass the rear air?My main concern is the rear air was bypassed correctly. Also what model do you have the C1500 C2500 K1500 or the K2500?When you replaced the ac compressor did you do what is called a oil balance procedure on it?11 ozs would be a full oil charge when only replacing part of the ac system you would only add part of that. Also the compressor wont kick on fully untill you add a couple of 12ozs cans or so a half of can isnt going to kick the ac compressor fully. Also you replaced the drier condensor orfice tube compressor and pressure switch?You mentioned the compressor blow valve on the back of the compressor blew off the brass one?If so why did the ac compressor kick on and the pressure went too high and it blew off?Also what are your concerns with the control head itself?

Saturntech9
Jul 28, 2012.
K1500. I did not hook up the rear air hoses. The low pressure line is broken at the rear of the truck. I only jumped the ac relay because I have no power to low pressure switch. I assume that the cycle switch blew out because I didn't have the snap ring all the way in. Or it blew because I put too much pressure on it while adding freon, because it wasn't working properly.

Tiny
Czr1760
Jul 28, 2012.
Alright you answered some of my questions the blow off valve both pieces screw in I dont see a snap ring. Also just the can pressure without the ac cmpressor shouldnt cause that valve to blow off. You need to replace that blow off valve if it blew off. My question is so its set up hose wise etc just like the system that doesnt have rear air?Both those hose going to the rear have been changed?Also please answer the other questions I asked you iam flying blind here. The info you give me is all I have to go on. Also dont jump the pressure switch thats your safety to keep you safe and your ac system safe.

Saturntech9
Jul 28, 2012.
Ok. I filled aprx 4 oz of oil into the compressor. The hoses going to the rear have not been changed, they are disconnected and not being used. I installed all new switches. Low pressure on dryer, high on top of hose on compressor and cycle switch in the back of the compressor, that's the one that blew out. I pulled the ac relay and jumped the connection to make the compressor cycle. No power at the low side switch and don't think I have power at the cycle switch either. I thought the head, because I read about transistor going out.

Tiny
Czr1760
Jul 28, 2012.
How much oil did you get out of the old compressor you changed?Your supposed to measure the oil you get out of the old compressor then put that much back in the new compressor. If no oil comes out you put in 2 ozs also if there was oil in the new compressor that should have been drained out. Was there metal in the ac system like the orifice tube etc from the compressor failing?Also you said the hoses are disconnected to the rear I hope new hoses were installed to hook it up like it should be for a none rear ac system?Also the a/c high pressure cutout switch on bottom rear of the ac compressor and the ac compressor cycling switch on top right of the ac accumulator. Those switches the black wires with a white strip go to ground thats why there is no power there switches. If you had power also you would have a dead short to ground.

Saturntech9
Jul 28, 2012.
Let me ask, do I need to hook up the rear ac lines, because I wan't planning on it. They are currently disconnected in the engine bay. The low pressure line is broken at the rear of the truck where it goes through the floor. Can I just not hook the front using my existing hoses? Also, no oil came out of the old compressor, it was locked and fried, who knows for how long. I didn't see any metal anywhere when I replaced everything. No oil in new compressor. And I'm sure I lost half of the oil that I just put in when the cycle switch blew out. I'm going to remove the compressor and re-install the switch now. I'm pulling the compressor off, because I want to make sure that the snap ring is seated all the way and I can't do that with the compressor installed. Then I can hook everything up and vac out the system. Let me know where I should go from there.

Tiny
Czr1760
Jul 28, 2012.
How much oil have you put in?I guess your just not understanding what I was asking it doesnt matter if the rear is unhooked. My concern is that the hoses etc are now hooked up like a none rear air ac system?If it is were good there.

Saturntech9
Jul 28, 2012.

AD