Ac compressor won’t engaged unless using a wire

[GoToGuy]

Do you have power to the low press connector?

 

[Road Trip]

So can anyone help me figure out what’s going on because the compressor itself doesn’t have power no matter what I do unless I put a wire up to it and bypass all switches.

Starting in '96 the VCM is involved in engaging the A/C compressor clutch.

Taken from Vol. 2 of the '96 FSM:

You must be registered for see images attach

This is just the first page of 3 pages worth of A/C compressor clutch diagnosis charts. Don't
know if you are aware, but we've got a thread with links to all the GM FSMs (Factory Service Manuals)
for the GMT400s. Do yourself a big favor and download these at your earliest opportunity. ('88+ FSMs)

Betweens these manuals and the talent in this forum, you should have this sorted out in short order.

Cheers --

 

[chandlerstovall]

Starting in '96 the VCM is involved in engaging the A/C compressor clutch.

Taken from Vol. 2 of the '96 FSM:

You must be registered for see images attach

This is just the first page of 3 pages worth of A/C compressor clutch diagnosis charts. Don't
know if you are aware, but we've got a thread with links to all the GM FSMs (Factory Service Manuals)
for the GMT400s. Do yourself a big favor and download these at your earliest opportunity. ('88+ FSMs)

Betweens these manuals and the talent in this forum, you should have this sorted out in short order.

Cheers --

FOUND THE PROBPEM
IT WAS A SWITCH ON THE BACK OF TJE COMPRESSOR!!

 

[1madmouse]

Really don't need to yell, just saying.

 

[chandlerstovall]

Really don't need to yell, just saying.

Sorry sorry

But I’m having another problem. The ac after awhile it’ll be fine one day but another day it’ll have too much pressure inside the system and it’ll cycle.

 

[GoToGuy]

Try that again. How can it be normal one day then be overpressure the next? Are you servicing it in your sleep or someone sneaking in at night. How do you know it's overpressure? " It'll cycle " what ?
When there is demand for AC the compressor cycles ( operates, on , off ) to make pressure for the air conditioning.
Correctly serviced with refrigerant, there is a chart that has high and low pressure values corrected for OAT and humidity, in FSM HVAC section.

 

[Schurkey]

The ac after awhile it’ll be fine one day but another day it’ll have too much pressure inside the system and it’ll cycle.

If the compressor is cycling excessively, the usual problem is too LITTLE pressure in the system--low refrigerant charge.

Adding refrigerant to full capacity causes the compressor to run steadily--DEPENDING ON TEMPERATURE. The clutch is going to cycle when the temps are lower. Cycling the clutch is how GM claimed "better fuel economy" in the '70s; before that the compressor just ran constantly whenever the A/C was requested. "CCOT" stands for "Cycling Clutch, Orifice Tube".