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Ron, ASE Certified Technician
Category: VW
Satisfied Customers: 35026
Experience:  ASE Certs.
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No power to the ac compressor, No voltage at all at the

Customer Question

No power to the ac compressor
JA: Is the power loss consistent, or does it fluctuate?
Customer: No voltage at all at the compressor plug with ac on
JA: What is the model/year of your VW?
Customer: 2000 Jetta gl 2.0
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: Yes want to work it out myself far I replaced Cts and the pressure switch
JA: Anything else you think the mechanic should know?
Customer: My fans don't come on when ac is on at all but they do come on while regular driving
Submitted: 9 months ago.
Category: VW
Customer: replied 9 months ago.
I also installed a new fan control module...but compressor witch is brand new still did not have power .and it made my rad. Fans spin at hi speed even with the engine off so I Had to pull the top fuse to the left of the other two green ones on top of battery
Expert:  Ron replied 9 months ago.

Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here. Providing the system is full and the pressures are correct then in order to determine why the compressor is not engaging you are going to need to do some testing. I have enclosed the steps in the link below.

Customer: replied 9 months ago.
Hi Ron thanks for the help ...i just tried to use the dropbox link you provided and it does not go anywhere
Customer: replied 9 months ago.
It has a 404 error
Expert:  Ron replied 9 months ago.

The post time out over time . I have reposted it. Be sure to print it out so as to not loose it.

Customer: replied 9 months ago.
Thank you do I get duty cycle with a multimeter? I heard it possible if a duty cycle meter is not available
Expert:  Ron replied 9 months ago.

You can ready a duty cycle by using the AC mode on your meter.

Customer: replied 9 months ago.
Should the plugs remain connected while doing the testing?
Expert:  Ron replied 9 months ago.

which plug are you checking?

Customer: replied 9 months ago.
The 14 wire connector on the fcm
Expert:  Ron replied 9 months ago.

Okay then it needs to be plugged in while testing

Customer: replied 9 months ago.
Ok...right now I'm trying to determine where the open circuit is .Because my fans work when I turn on the ac but compressor does not work ,unless I jump it with 12 volts
Expert:  Ron replied 9 months ago.

Are you working on a manual Ac system or is this an automatic. I look you up a wiring diagram. Let me know.

Customer: replied 9 months ago.
I think its manual , because it has all the ac controls and stuff on the dash
Expert:  Ron replied 9 months ago.

Yes that would be correct , see the system wiring diagram in the link below to see if this will help you trace the open .

Customer: replied 9 months ago.
Thanks for that diagram...i got delayed a bit because my heater hose broke ...i keep getting a 3 on the multimeter when checking the grounds , is that about right?
Expert:  Ron replied 9 months ago.

If you checking a ground you should not be reading any voltage on the ground circuit.

Customer: replied 9 months ago.
If the fcm is good...should there be a constant 12v at compressor, or does it switch on and off during ac use?
Expert:  Ron replied 9 months ago.

The AC compressor will normally cycle off and on during normal operation to avoid the system freezing up.

Customer: replied 9 months ago.
Would you help me with step 11 in the first link you gave me ? i'm not quite sure what it means
Expert:  Ron replied 9 months ago.

What type of help are you needing, I am limited with what I can do from here.

Customer: replied 9 months ago.
It says to cut the ecu signal wire...but what is the wide open throttle about?
Expert:  Ron replied 9 months ago.

The system is designed to shut the AC compressor off during wide open throttle operation to cut the load on the engine.