QuestionQUESTION: On A 2002 Ford Escort, I drained the system, put a vacuum on it and recharged it. The problem is I can't get the compressor to engage. I checked to see if there is fire to the electrical connector but there is none. On any other vehicle I've ever worked on the compressor will engage after one can of refrigerant. I can't figure this out. Really would appreciate it if you could help me out, thanks.
ANSWER: Rick,
I believe that you will find that there isn't enough pressure in the system to close the contacts in your low pressure switch. I want you to check there first. With a jumper wire, the key in the run position, and the A/C switch on... unplug the wiring harness from the switch and jump the wires inthe plug. If your compressor clutch still doesn't "snap" do a follow-up with me and I will talk you through the schematic from there.
I hope this response helps a bit. If not... as I said let me know and I will run you through it.
Thank you for the question and good luck in everything. Please remember to rate this answer.
---------- FOLLOW-UP ----------
QUESTION: David, I did as you said and jumped the wires in the plug and the clutch still did not kick on. I did notice a change in engine RPM when I did this. Thanks.
AnswerRick,
When you jumped the low pressure switch, the only time it should have changed the rpms at all is if the clutch engaged. That is odd... But I have pulled up your wiring schematic and am looking at it now. For some of these tests, you will need a multimeter.
Ok, first things first. Check the A/C fuse. You should have only one fuse for your A/C system. It is located in the passenger compartment fuse box. It is a 15A. Is this fuse good?
From there voltage splits to your WAC relay contact (normally open)and your selector switch. If you set your selector switch to MAX A/C... Voltage then travels to your Low pressure switch Orange wire. The low pressure switch is located in the right front of the engine compartment on your accumulator. Do you have voltage there? You should read 12 volts on your multimter. If you do not... the problem lies in your selector switch. If you do... plug this back in.
Voltage now travels to your high pressure switch green and red wire. The high pressure switch will be located on your high side line in the left front of the engine compartment. Do you have voltage here? Should be 12 volts. No? Go back to your low pressure switch and jump the terminals in the plug. Now do you have voltage on the green/red wire? From here voltage travels to the PCM (Powertrain control module) located below the center of the dashboard. Let's assume this is good so you don't have to pull it out and check. From there it travels out of the PCM on the Blue/Black wire back to your WAC relay
only this time it hits the coil portion of the relay. This relay is located in the the relay box in the front left of the engine compartment. Unplug this relay and check the socket connector that has the blue/black wire connected to it. You should read 12 volts. If you do not... go back to your high pressure switch and jump the green/red wire to the green/black wire. Now do you read 12V at the blue black wire where it connects to the WAC relay? No? The problem is inside your PCM. Yes? Plug the relay back in. Did your clutch engage? No? Check your compressor ground wire to make sure it is tight and has no corrosion that would prevent it from grounding. If you have a good ground... unplug the relay again and jump the connectors with the white wire to the connecor with the blue white wire. Did your compressor engage? Yes? Replace your WAC relay. No? The problem lies in your clutch itself.
Now jumping back to the first time we plugged the relay back in (7 lines above). If your compressor engaged... Un-jump your high pressure switch and plug it back in. Is the clutch still engaged? No? replace your high pressure switch, the contacts are open when this is supposed to be a normally closed switch. Clutch is still engaged? Unjump your low pressure switch and plug it back in. Clutch still engaged? No? Check your refrigerant charge one more time. If you have at least 30PSIG inside the system replace your low pressure switch, it is not closing its contacts when you have enough pressure in the system.
And that is your entire A?C schematic. I tried to be as user-friendly as possible, but if there is something in there that I need to clarify (I tend to confuse myself when I get to typing about voltage checks) I will be more than happy to do so. But with the checks above, the only thing I didn't go into is the PCM itself, because that is very in-depth. And a mistake in checking it could result in "frying" it. If you narrow it down to this being the fault, take it somewhere and have them check it out.
I hope this helps. If you can read schematics and follow the flow of electricity, I can send you a copy of them to an email address if you like. Just make sure you post that follow-up as private so the world doesn't get ahold of your address.
Again, thank you for the question. If I can do anything further now or inthe future, do not hesitate to ask. Or if you would like me to send a copy of the schematics, feel free to ask. Good luck in everything, and once again... please remember to rate this answer.
