ac compressor not turning on
ac compressor not turning on I was doing an evac on my ac system and when I tried to give it a charge I noticed that the ac compressor was not turning on.I replaced the compressor about a year and a half ago.I pulled the connector on the compressor and noticed the voltage on the connector was 30 mv with the ac on. I swapped the fuel pump relay and the compressor relay and no change.
Does somebody on here have a wiring schematic for the ac wiring or diagram?What should I try next? What voltage should I see on that connector with the ac on and on max?Any suggestions? It is a 2000 pontiac trans am 5.7
Does somebody on here have a wiring schematic for the ac wiring or diagram?What should I try next? What voltage should I see on that connector with the ac on and on max?Any suggestions? It is a 2000 pontiac trans am 5.7
Ac compressor won't engage until the low side and high side have minimum safe operating pressure. The clutch will not engage unless you have freon in the system
Voltage typically goes from high side switch to low side switch, to the fan, and then to the compressor
Voltage typically goes from high side switch to low side switch, to the fan, and then to the compressor
I changed the o rings because the ac system was leaking.When it had a charge I never heard the compressor turn on a few days ago.Don't you need the compressor to turn on to suck in the 134 into the system?There is a fuseable link or something in the wiring above the ac compressor connector.I figured that I would check the voltages at the relay and see if there was something there.
Checked the voltages on the ac compressor relay. On the relay #30 0 volts #87 12 volts
Those 2 pins are the switch side of the relay #85 ground #86 no voltage with the air conditioner switch on.There is no power to operate the ac relay.What Should I check now?
Those 2 pins are the switch side of the relay #85 ground #86 no voltage with the air conditioner switch on.There is no power to operate the ac relay.What Should I check now?
Last edited by transwiz; Jun 20, 2017 at 12:19 AM.
Joined: Nov 2003
Posts: 11,328
Likes: 345
From: Jacksonville, FL (originally from Toronto Canada)
The AC system (and particularly the relay) is not directly controlled by the dash switch. The switch merely provides an AC Request signal to the PCM which then manages the relay by providing ground to the coil side through the dark green/white wire. That would be either pin 85 or 86 on the relay (the schematics show the connector pin numbers not the standard relay terminal numbers). Both the relay coil and the relay switch sides are powered through a pink wire from the AC/Cruise fuse in junction block #2 under the hood.
That means that it is extremely unlikely (almost impossible) for you to have power on terminal 87 but not on 85/86 - they both get power from the same place. The only way that could happen is if there was a break in only one pink wire someplace between the splice where the two split and the relay socket. I suspect you aren't measuring correctly... you need to put the positive probe to the relay terminal and the negative to a good ground such as a chassis bolt. Measuring across the terminals will always read near zero because you are measuring the voltage drop rather than the source voltage.
First, pull the relay and check for power in the socket. You should find power on both pins with pink wires. Next, leave the relay out and use a jumper wire to connect one pink with the dark green (your 87 and 30 terminals). If the AC clutch engages then you know the problem is either the relay itself or the PCM not providing ground to the relay coil to activate it. You can determine which by swapping a known good relay from one of the other positions in the junction box.
That means that it is extremely unlikely (almost impossible) for you to have power on terminal 87 but not on 85/86 - they both get power from the same place. The only way that could happen is if there was a break in only one pink wire someplace between the splice where the two split and the relay socket. I suspect you aren't measuring correctly... you need to put the positive probe to the relay terminal and the negative to a good ground such as a chassis bolt. Measuring across the terminals will always read near zero because you are measuring the voltage drop rather than the source voltage.
First, pull the relay and check for power in the socket. You should find power on both pins with pink wires. Next, leave the relay out and use a jumper wire to connect one pink with the dark green (your 87 and 30 terminals). If the AC clutch engages then you know the problem is either the relay itself or the PCM not providing ground to the relay coil to activate it. You can determine which by swapping a known good relay from one of the other positions in the junction box.
once the ac system is evacuated {to under 1000 microns pressure} then anything having a higher pressure than what the ac system is at will flow in to it. So all you would have to do is connect a bottle, or can, of r134a which would be at 70psi @ 70°F. so no, in this case you don't need the compressor running to suck refrigerant into the system
I replaced the ac pressure sensor switch on tone of the lines. Evacuated the system and everything looked good. Re charged the system with 134 and so far so good.The compressor
turned on and took the charge. The next day I checked the lines with a black light and found that it was leaking from the lower compressor hose.All the charge leaked out. I ordered a new hose and when it comes in I will pull the compressor and install the hose with new o rings.Then I will try it again.
The electrical connections checked out on the relay.What A pain this has been.
turned on and took the charge. The next day I checked the lines with a black light and found that it was leaking from the lower compressor hose.All the charge leaked out. I ordered a new hose and when it comes in I will pull the compressor and install the hose with new o rings.Then I will try it again.
The electrical connections checked out on the relay.What A pain this has been.
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I had an issue with my 95. The datalogger showed no pressure reading coming from the AC pressure switch. Replaced the sensor and still had the issue.
Turns out the pins inside the plug were bent not making contact with the sensor.
Turns out the pins inside the plug were bent not making contact with the sensor.
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