A/C compressor is not turning on

Never mind fan is on, but still 2 wires at compressor are showing ground

Hi,

At the compressor, you should have a black wire (which is ground) and a black wire with a yellow tracer (which is power).

If you disconnect the connector from the compressor, with the engine running and the AC turned on, do you get power to the black/yellow wire? That wire comes from the compressor relay and should power the clutch coil, so it engages.

Check that and let me know what you find. As far as the wires, if you have continuity to ground via the black/yellow, pull the compressor relay and recheck. If it still shows ground, the wire must be pinched or broken and is shorted to ground.

Here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-check-wiring

Also, I attached the wiring schematic below of the A/C system for your reference.

Let me know what you find

Take care,

Joe

See pics below.

I am having a problem recognizing where the A/C clutch relay is. I thought about removing the compressor's wire and checking for power and ground but didn't do it. Will do that first.

Removed the wire, there is ground, there is no power but sometimes i get a reading that isn't power cause the probe doesn't light or beep and it reads 9.9.

Hi,

Is that 9.9v? If it is, the light should turn on. Do you have a different way of testing it other than the test light? You could use a voltmeter or multimeter. Also, you indicated the 9.9v is sporadic. How much of the time is it non-existent?

Let me know.

Joe

Didn't say 9.9v just 9.9 no beep or light and not always there. I am using a probe and if its volts/power it would beep. I have a regular test light as well.

Okay, I'm not familiar with the tool used that provided the 9.9. However, if you used a test lamp and it never turned on, it can't be getting power.

By chance, have you checked for voltage at the relay?

Joe

It's a regular probe. I don't know where the relay is or which one in the box and how do i test it or jump the wire to see if the compressor kicks on?

Hi,

According to the manual, the relay is mounted on a bracket behind the engine. If you want to test it, here are the directions for checking a relay.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Let me know if this helps.

Take care,

Joe

Do you know where behind the engine? Some videos show it behind the fender liner.

Hi,

Check behind the coolant reservoir. It should be located in the constant control relay module. Keep in mind that some of these relays are integral. If that is the case, the module would need to be replaced. And based on the model year, that may be the case. I attached what the CCRM looks like on the newer Mustangs. See if this is what you find. And as far as the relays are concerned, they are integral. I believe you can take it apart, but the relays are usually soldered onto a printed circuit board.


Let me know.

Joe

Replaced the relay module and all is good. Thanks

Hi,

You are very welcome and thanks for the update. I'm glad to hear it's working.

Take care of yourself and please feel free to come back anytime in the future.

Joe