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.
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Czr1760
July 28, 2012.




I guess I'm not understanding then, I'm sorry. Should I try and follow the ground on each of these plugs to find out where it is grounded? Or are you saying that nothing will have power until I have enough charge into the system? I'm not sure that I understand what you are saying with a dead short either. Sorry, please explaing. Thanks.

Tiny
Czr1760
Jul 28, 2012.
Alright lets this again the black wire with a white strip is supposed to have a ground it. That is the ground for the ac relay when the switch is tripped it turns the ac clutch off from the relay side. Also the ac compressor isnt going to come on or stay on till there is enough pressure in the system like I said in a earlier post.I hope this makes sense now?

Saturntech9
Jul 28, 2012.
But isn't power initiated from the control head? Should I not have power to the plugs? I have no porblem ground anything directly to the damn frame at this point, I jsut want the ac to work. I can't put freon into the system without any power, because when I tried that before, the low pressure just kept going up. If the compressor doesn't cycle then I can't keep putting freon into the system. That's why I tried to jump the compressor. I'm about to run a switch to battery power and hook it up to the compressor or just jump the thing again. At least when I did that the compressor would turn on. I'm still curious how I'm supposedto find out where the ground issue is at and why I don't have any power. Now it's too late in the day to head to the junk yard to find a new head unit. Ugh. This is so frustrating and I feel like I'm getting no where at all!

Tiny
Czr1760
Jul 28, 2012.
Great, now we have a wonderful Florida monsoon! Ok, do you have a procedure for checking power to the system? Should I start at the control head (key on/ key off) and report findings.

Tiny
Czr1760
Jul 28, 2012.
Your not getting it there is now power to those pressure switches. They have a ground feed and when the switch is closed it supplys the ground to the ac relay. If there is a pressure issue high or low it will take the ground away from the ac relay. Its normal for the low pressure to go high like a 100psi or so while the ac is being chargee that pressure will starting dropping when the ac system gets more charge. How much charge have you put in so far?It will probably take a can or so in the system just to get the ac clutch to come on and start cycling. Also about 2-3 cans before the ac clutch stops cycling. As far as jumping something to charge it I have never had to do that or would do that. Iam certainly not going to tell you how to do something I wouldnt do or think is unsafe. Start the engine with ac button pushed and the blower fan on high. Then start charging the ac system thru the low side the ac compressor will start cycling while its charging. Keep charging it and the compressor will stay on solid.I have done this too many time to count. Even with the ac buton sending the signal too the ac relay the ac clutch will not engage until the pressure switch see the correct pressure.
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Saturntech9
Jul 28, 2012.
Ok, I took your advaice and I worked! 3 cans and I've got 48 lbs. Low side and 195 lbs. High side. The reason that I was questioning was becuase I tried the same thing before and the low prssure side just kept going up and the compressor NEVER cycled. That was another compressor that I had purchased from Advance. I took it back and ordered everything online to save some cash. Maybe I just had a "bad" new compressor before. That's why I've been so puzzled and why I didn't want to keep throwing money away. No matter what, it's working now and I'm so happy. Thank you so much for all your help. I'm glad that I didn't go get a new control unit to boot.

Tiny
Czr1760
Jul 28, 2012.
Your welcome thats what were here for. Iam glad you finally listened I have been working cars since I was kid.I really try not to waste peoples money also looks like one more 12oz can of charge and you will have a full charge sine yours holds 3LBS or 48ozs. Also I hope you added some dye like I said in case you have a leak somewhere?Glad to hear it worked out you just needed a like guidance.

Saturntech9
Jul 28, 2012.
You think I should add one more can of freon? Even though I had 49 lbs low side.

Tiny
Czr1760
Jul 29, 2012.
The system without rear air holds 3Lbs I always put in what the system holds.

Saturntech9
Jul 29, 2012.
Ok, I'll pick up another can and install. So just put the 4th can in and don't worry if my low side pressure goes up? Is there a pressure that I should consider too high? Thanks.

Tiny
Czr1760
Jul 29, 2012.

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