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Ron
Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 34149
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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I have a 2002 ford f150 4.6 liter that the ac compressor

Customer Question

I have a 2002 ford f150 4.6 liter that the ac compressor will run for 5 second then shuts off. The system is full. I did an evacuation and recharge. The fuses in the the box is grounded like a bad fuse box (I'm using a power probe 3). The wires on the low pressure switch are ground also.
JA: Have you checked for a blown fuse?
Customer: All of the fuses are good If I close the relay the compressor will engage
JA: Are you fixing your F150 yourself? What have you tried so far?
Customer: Yes. I'm a Honda Technician trying to help a friend
JA: Anything else you want the mechanic to know before I connect you?
Customer: That's it
Submitted: 5 months ago.
Category: Ford
Expert:  Ron replied 5 months ago.

Hello. My name is ***** ***** I am happy to assist you today. Give me just a moment to review your post, and I'll be right back with the help you need.

Expert:  Ron replied 5 months ago.

Do you have access to a scan tool that can read the Pids?

Is this an automatic system (buttons ) or manual (knobs)?

Customer: replied 5 months ago.
Ok
Expert:  Ron replied 5 months ago.

Do you have access to a scan tool that can read the Pids?

Is this an automatic system (buttons ) or manual (knobs)?

Customer: replied 5 months ago.
It's a manual system. Can hook much maximus up and check the data
Customer: replied 5 months ago.
My maximus
Customer: replied 5 months ago.
The a/C pressure switch open (ok)
Air Conditioning Clutch off
Air conditioning cycling switch on
Expert:  Ron replied 5 months ago.

Okay see the testing steps in the link below for checking the clutch operation and I have also enclosed the wiring diagram for the system for testing reference. Have a look and see if these steps will help you get this resolved.

https://dl.dropboxusercontent.com/u/104923897/AC%20clutch%20Sept%209.pdf

https://dl.dropboxusercontent.com/u/104923897/Clutch%20wiring%201%20Sept%209.pdf

https://dl.dropboxusercontent.com/u/104923897/Clutc%20wiring%20Sept%209.pdf

Customer: replied 5 months ago.
The compressor works. Once the vehicle is first started the compressor runs for 3-5 seconds. If I send ground to pcm pin in on the relay the compressor will engage and high and low side pressures are within spec
Expert:  Ron replied 5 months ago.

The ground is supplied to the relay from the PCM and if the TP sensor is not stuck in the WOT mode then that usually means the PCM is at fault. Are you getting any fault codes?

Customer: replied 5 months ago.
I will check the to sensor now. It's a new pcm in it now that another shop installed it. I had to program new keys to it
Expert:  Ron replied 5 months ago.

Have a look at your TP voltage to be sure its reading closed throttle and that the voltage comes up when you open the throttle as well.

Customer: replied 5 months ago.
The tps is working perfect. It's ct at idle, pt when slightly depressed and wot at wide open.
Customer: replied 5 months ago.
TPS at idle is .0967742 volts
Customer: replied 5 months ago.
Throttle position rate is 1316
Expert:  Ron replied 5 months ago.

The TP looks normal . Okay then you loosing your ground from the PCM, I would suspect the new PCM is defective especially if the system cools properly with the relay grounded.

Customer: replied 5 months ago.
The underground fuse box has positive on fuses when off. When running the positive voltage pulsates on every fuse
Customer: replied 5 months ago.
Underhood
Expert:  Ron replied 5 months ago.

There are known issues with the windshield leaking on the 2002 F 150s where water leaked in and dripped on the interior fuse panel and the GEM module which mounts to the top of it, is the voltage steady on the interior fuse panel as well?

Customer: replied 5 months ago.
It's the same on the inside fuse box also
Expert:  Ron replied 5 months ago.

What is the voltage reading at the battery, is it pulsing as well?

Customer: replied 5 months ago.
Battery voltage when off is a steady 12.6 volts and battery voltage while running as a steady 14.1
Expert:  Ron replied 5 months ago.

Dose not make since if it pulsing at the fuse panels. Battery voltage at the fuse panels should read the same as the battery voltage at the battery.