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Lou P.
Lou P., Technician
Category: Classic Car
Satisfied Customers: 4959
Experience:  I currently own a 1969 and 1972 CAMARO and have 15+ years of training and knowledge!!!!
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I have a 1971 El Camino SS with the Ls5 454. The car is a

Customer Question

I have a 1971 El Camino SS with the Ls5 454. The car is a restoration that is 95% finished. My problem arises with the A/C electrical. Keep in mind all the wiring is new but original relays ect. The compressor is a factory rebuilt with new clutch.
The problem..... when the air is turned on, the compressor clutch slightly drags or not at all. I disconnect the two wire connector off of compressor and check voltages. The hot side measures 13-14 volts, however when it's connected to the compressor it measures only 2-3 volts. Thus not giving the clutch enough voltage to engage. I have tested the clutch by putting a jumper from the battery, and the clutch locked up every time and is cold. I don't want to be just a parts changer to find my problem.
Please help.
Submitted: 1 year ago.
Category: Classic Car
Expert:  Lou P. replied 1 year ago.

Hello, my name is***** and i will do my best to assist you.I am going over your story now and will reply back soon with some info,thanks!

Expert:  Lou P. replied 1 year ago.

ok so when you disconnect the connector i want you to measure from the ground wire to engine ground and tell me the resistance, it should have very close to 0 ohms. if any. lets make sure the ground side is good.

Customer: replied 1 year ago.
It measures .3 ohms . As I mentioned before, using the factory ground on the connector and using a jumper directly to the battery. It locks up the clutch fine. Crazy thing is , un-plug the harness I have voltage. plug it together I have 2-3 volts. Then un-plug its back to 13-14 volts.
Expert:  Lou P. replied 1 year ago.

ok so it is possible the meter is switching to voltage drop, you said the wiring is new correct? what about the other end does that wire go to a switch ? i have to see if i can find my diagrams.

Customer: replied 1 year ago.
Please review your diagrams. There are switches and relays ect.
Expert:  Lou P. replied 1 year ago.

ok i see a black ground and a dark green power wire at the compressor ? confirm?

Customer: replied 1 year ago.
Correct
Expert:  Lou P. replied 1 year ago.

OK GOOD DEAL

Expert:  Lou P. replied 1 year ago.

it goes to a thermal switch and comes out a tan wire.

Expert:  Lou P. replied 1 year ago.

so lets bypass that switch and see if the compressor works , we can have a faulty or weak thermal switch.

Customer: replied 1 year ago.
The two wire ambient switch has green and light blue wires.
Expert:  Lou P. replied 1 year ago.

then its the wrong switch, follow where the dark green power wire of the compressor goes. there is a thermal switch that opens the circuit when the wiring gets hot from compressor activation.

Customer: replied 1 year ago.
I contacted the mfg of the harness. The two wires green & light blue are correct. The tan is a error on Gm's documents.
However, jumping the switch made no difference.
Expert:  Lou P. replied 1 year ago.

ok, so far so good. then after that the wiring goes to the ac switch on the panel. the lever that you slide to get the ac on. we need to bypass there as well, and see, this is the only way we can determine where the voltage or amperage is lost, what kind of fuse does it use? the oem glass fuse in the fuse box?

Customer: replied 1 year ago.
The switch on the control register is being replaced due to being damaged. But it's connector is jumped and shows the same voltage drop.
Expert:  Lou P. replied 1 year ago.

OK, so far so good we are at least eliminating items. all news is good news.

Expert:  Lou P. replied 1 year ago.

let me as you this, when you are testing the available voltage when the compressor is hooked up are you checking from the positive wire to the chassis ground on the engine or are you testing across the connector pins positive and negative?

Expert:  Lou P. replied 1 year ago.

what if you wiggle the connector on the compressor, maybe the terminal is the issue right there at the compressor, another test would be to get a light bulb socket or light bulb and use that as the load, lets see if we get the same issue with something else connected to that connector, do you know where i am going with this?

Customer: replied 1 year ago.
Both ways. Hot side , tested to ground bolt, connector, and to the battery. All the same
Expert:  Lou P. replied 1 year ago.

ok, so do the test i just posted, lets see if a light bulb would be dim or bright, just to confirm its not the compressor and its the vehicle side.

Expert:  Lou P. replied 1 year ago.

http://www.elcaminocentral.com/articles/wiring/69/69wiring.jpg

here is the diagram i am referring to , it does say 68 but should be for all models of that era.

Customer: replied 1 year ago.
Still not working
Expert:  Lou P. replied 1 year ago.

Sorry I will opt out and let another expert help.