Ford Expedition 2004 5.4 2V AC Compressor Does Not Engage / I tried everything I know

[denizkaya]

Hi. Please help us on what we can do to fix my truck's AC. It hasn't been working since I bought it and I'm determined to fix it now. Let me explain what I did so far:

-New AC Compressor Clutch Relay (didn't work)
-Jumped both the switches in the pressure lines
-Checked all the fuses and relays related
-Checked AC compressor socket (it is getting 12V)
-Jumped AC compressor with 12v, clutch engages
-Checked the diode, it works
-There is enough pressure as far as I see. Regardless, jumped all the switches so the compressor is supposed to run whether there's pressure or not (I guess)
-Jumped ambient temperature sensor
-Checked the digital panel button, it works. AC compressor clutch socket gets 13v when AC is open and 0v when it's closed




When I jump 30 and 87 in the AC compressor clutch relay, I don't get voltage in the AC compressor socket.

The radiator fan starts to work as soon as I start the truck. I don't know why.

I haven't checked any amperage on the cables. Can that be an issue?

If I'm getting 13v on the socket, why doesn't my compressor engage? And why does it engage when I jump it through the battery?

I'm about to lose my mind. Please help me lol

 

[whtbronco]

So it appears you have checked everything except maybe the wires. A voltage drop test seems to be in order here. I'd start with the wires at the compressor and work out from there.

Voltage Drop Testing Explained | Technician.Academy

Voltage drop testing is a diagnostic strategy that uses a digital multimeter (DMM) or a similar tool to test actual circuit voltage and compare it with a desired circuit voltage.

technician.academy

The fan being engaged at startup with a mechanical clutch is normal. They usually disengage after a few minutes depending on the temperature. Only electric fans are directly tied to the A/C.

 

[AWAR]

Check the ground on the wires to the compressor.

 

[denizkaya]

Checked

So it appears you have checked everything except maybe the wires. A voltage drop test seems to be in order here. I'd start with the wires at the compressor and work out from there.

Voltage Drop Testing Explained | Technician.Academy

Voltage drop testing is a diagnostic strategy that uses a digital multimeter (DMM) or a similar tool to test actual circuit voltage and compare it with a desired circuit voltage.

technician.academy

The fan being engaged at startup with a mechanical clutch is normal. They usually disengage after a few minutes depending on the temperature. Only electric fans are directly tied to the A/C.

We'll try it. We were thinking maybe the connector is bad since we are getting 12v from the connector head, but still we get no power to the compressor. We jumped the compressor from the battery, clutch engages. Then we tried to jump the cable that runs to the connector, we saw no power still. What do you think?

Check the ground on the wires to the compressor.

I physically checked and it looks fine. Is there a way to test it through multimeter?

Thank you all guys

 

[AWAR]

Yes, but use a test light on the ground to give it a little load. A meter applies zero load, that is why you use them on computerized circuits.

 

[whtbronco]

The other option is the voltage drop which will test both power and ground wires.

I don't use an actual test light anymore, there is a load, but I was told and proved that it's a very minimal load. An LED test light is likely near worthless since the power required is so low. What I was told was to make a test light from a turn signal or brake light. I took an old brake light connector and lengthened the wires. The brake light bulb applies enough current draw to prove that the wires can support a legitimate current draw.

It certainly sounds like you have narrowed the failure to the wires to the compressor though.

 

[Dustin Gebhardt]

I commuted into Mexico 4 to 5 days a week. Sitting and idling in the border line for hours at a time in the summer heat were miserable as my AC couldn't keep up. So I added 2 electric fans to the front of my condenser. They were powered through a relay, which got the on/off signal from the power wire going to my AC clutch. I mention this because if your AC clutch is getting power, then it should engage the clutch. As others have said, a bad wire can limit current, which can prevent the clutch from engaging. You may want to splice into your clutch power wire and apply a jumper direct to your battery. If the clutch engages, then that section of wiring (from the splice to the clutch) is good. You can then create a new splice further up the chain and retest.