Strange AC issue....

[Lockdown]

Hello all; I've been using this forum through Google searches for many different issues over the last few weeks, so thanks to all for the volume of information.

I recently picked up a mint 2004 Ford Explorer Limited 4x4 4.6L V8. For an 11 yr old truck, it's in better-than-great shape and has 109,000 on the od. Through this forum I've been able to work out some of the kinks the truck had, and two remain... one I'm working on with someone at the moment (fuel gauge works in reverse order).

The subject presently is the AC. When I bought the truck it worked perfectly. That was two weeks ago. Now, about every 5 days, it starts to blow warm air. This may last a few days or only 24 hours. When it is blowing warm air, the AC compressor is not kicking in, so that's why it's warm air... BUT, again, I don't know when it will start blowing cold again.

I've cleaned out the low pressure connector; that fixed it the first time.

I've had a mechanic clean out the wire connector that's on the compressor; that fixed it the next time.

Yesterday, the AC went out on it's own again. This occurred after driving it around town on and off for about 50-75 miles (my wife normally takes this to/from work only - about 40 miles round trip). I played with the low & high pressure wire connectors, no luck (you can hear the engine idle change as I unhook the connectors). I let it sit overnight, and this morning it was working fine again. A few trips around town with the truck being turned on & off, and the AC quit again (only blowing warm air).

I cleaned out that connector on the compressor, no luck.

Soo... any ideas why the compressor will work perfectly for days on end, then simply stop? I have an appointment for next week to have it looked at, but even though it's October, here in Naples, FL; it's still 88 degrees outside!

 

[Bobmbx]

Your compressor clutch coil (the electromagnet) may be bad, and working intermittently, or the clutch is worn and doesn't have enough friction to turn the compressor.

Have you had the Freon pressure checked? That's usually the first thing to do when the AC gets wonky.

 

[Lockdown]

Your compressor clutch coil (the electromagnet) may be bad, and working intermittently, or the clutch is worn and doesn't have enough friction to turn the compressor.

Hhhmm... that would mean I'm waiting until next Tuesday to have the pro look at it... would it seem normal for this condition to allow the AC to run fine for days?

Have you had the Freon pressure checked? That's usually the first thing to do when the AC gets wonky.

I was going to pick up a can of R134 w/ the gauge, but it didn't seem to make sense to me if it would run for days, at least 45 minutes at a time, without issue. If it was low on Freon, wouldn't the low pressure make the compressor not kick in at all?

 

[Number4]

Could be an issue with the fan clutch as well.

 

[Lockdown]

I also just ran my hand along the wiring harness described as the cause of a similar-sounding problem in a similar truck: http://www.explorerforum.com/forums/showthread.php?t=287097

My wire harness felt intact; although I couldn't see the entire length of it, I could feel the protective covering was intact.

 

[Bobmbx]

Hhhmm... that would mean I'm waiting until next Tuesday to have the pro look at it... would it seem normal for this condition to allow the AC to run fine for days?



I was going to pick up a can of R134 w/ the gauge, but it didn't seem to make sense to me if it would run for days, at least 45 minutes at a time, without issue. If it was low on Freon, wouldn't the low pressure make the compressor not kick in at all?

If the clutch coil is working intermittently, yes, it could work for days, stop, then start working again. When an electrical component starts to do that, the causes are generally limited to an open wire (broken) or a short. Of those two, the open is more probable. It could be that as long as the engine/metal mass is below a certain temperature the wire is whole, but once everything warms up, the wire physically moves into the open state. That's just a guess about what may be happening to you.

You can test the coil by holding a screwdriver near the coil body and see if the magnet grabs it. Put the system on MAX AC with the fan on high. If the coil isn't grabbing the screwdriver when the compressor should be running, next step is to test power to the compressor itself using a multimeter.

You could also jump 12 volts directly to the compressor to activate the coil to test it.

 

[Lockdown]

That all makes sense; as I drive the truck more in the same day, it gets warmer. The prolonged drives seem to kick the problem off.

I think it is a wire issue. I just ran out and put the AC on the coolest setting with the fan on high. No compressor kick in. I then used a 36" metal rod to tap the wire harness on the compressor, and it kicked in immediately. Here's the harness I think the issue is with:

 

[Lockdown]

Guess I'm going to have to replace that connector... anyone have any idea what that's called or a part number?

 

[Joe in NY]

Pull it out and see if the pins are dirty/corroded. It might just need a cleaning.

Also, really inspect the wiring harness. The spot it goes bad is right above the oil filter drain shield. Mine at 60,000 miles was through the harness cover and starting the wires... I taped it and bent the bracket up to pull it away from the sharp edge of the shield.

 

[Number4]

I also just ran my hand along the wiring harness described as the cause of a similar-sounding problem in a similar truck: http://www.explorerforum.com/forums/showthread.php?t=287097

My wire harness felt intact; although I couldn't see the entire length of it, I could feel the protective covering was intact.

For this issue, look at the filter drain catch (black plastic piece.) if the harness is near it, it's a good possibility. On my '04, the harness is secured a good distance from the drain. Don't know why some are free hanging and others aren't.

 

[Joe in NY]

it's not that they are free hanging...

On the early builds the bracket they used secures the harness right above the sharp edge. It is supposed to be there. Just over time the harness sags that extra little bit and touches the sharp edge and starts wearing through. Just have to simply bend the bracket up and the harness is more than clear.