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Lou P.
Lou P., Technician
Category: Classic Car
Satisfied Customers: 4085
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: 8 months ago.
Category: Classic Car
Expert:  Lou P. replied 8 months 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 8 months 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 8 months 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 8 months 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 8 months ago.
Please review your diagrams. There are switches and relays ect.
Expert:  Lou P. replied 8 months ago.

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

Customer: replied 8 months ago.
Correct
Expert:  Lou P. replied 8 months ago.

OK GOOD DEAL

Expert:  Lou P. replied 8 months ago.

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

Expert:  Lou P. replied 8 months ago.

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

Customer: replied 8 months ago.
The two wire ambient switch has green and light blue wires.
Expert:  Lou P. replied 8 months 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 8 months 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 8 months 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 8 months 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 8 months ago.

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

Expert:  Lou P. replied 8 months 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 8 months 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 8 months ago.
Both ways. Hot side , tested to ground bolt, connector, and to the battery. All the same
Expert:  Lou P. replied 8 months 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 8 months 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 8 months ago.
Still not working
Expert:  Lou P. replied 8 months ago.

Sorry I will opt out and let another expert help.

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