Exploder Air conditioning

[morgfarm1]

Alrighty, So my little blue boat is giving fits with the AC System.

It's strange to me, and i've gotten 2 different answers from 2 different people i'v e talked to.

It's 99 Limited, Loaded, so it's got that fancy pants Automated Climate system.

Setting the AC to Max, temp at 60, and at idle, the AC Blows nothing but cold.
But, When I use throttle, usually at speeds over 35mph, The AC air turns warm, but cools off again at an idle.
If I'm super gentle on the gas, and all but coast it through town, the air stays, sorta, cold. but normal driving kills the cool air.

I can't for the life of me figure why this is. One fella i talked to suggested the vehicle may have a sensor that determines that if I'm driving rough, it'll kill the AC and divert that energy all to performance to keep from overheating, and that sensor may be bad.
My normal mechanic figures it could be the condenser being plugged.
It could even be overcharged, but I can't tell. I just lost my job last month so it's tight, and with temps in the 90s, I need my air fixed. Any ideas so I can attack this in one shot and have a pretty good chance at resolving it? Thanks ya'll, I appreciate what you guys do for us Explorer noobs :exp:

Oh, and I've watched the AC Clutch, There are days it'll run intermittently (As described by many, Runs for 10 seconds, takes a break, and comes back) last time I looked with AC topped out, it seemed steady for a good 30 seconds.

 

[my98nnj]

You need to put a set of gauges on it to see what's going on. Have you added refrigerant to the system? If so it could be over charged, if not it's probably under charged and kicking off on the low pressure switch when the RPM's rise.

 

[bobflood]

There is a Wide Open Thottle (WOT) relay in the compressor circuit that kills the compressor under WOT conditions. It is controlled by the PCM; you might try unplugging that relay and putting in a jumper wire to temporarily eliminate it from the circuit. And it's a free test - just need a short chunk of wire.

 

[morgfarm1]

Bob, I think you're on to something. I just fired the engine off with AC on full, put a moderate amount of throttle to it, and the AC Clutch released. Laid back to idle, the AC Clutch reactivated. I have the wire to do the job, What do I Jump to where? And if, after the jump and test, The AC Clutch stays active, what do I replace next?

 

[bobflood]

Acording to the wiring diagram, the AC relay is in the Battery Junction box. Looks like you should jumper terminals 3 and 5 together. If that resolves issue, first thing to do is replace that relay. It could still be that the relay is OK and something else is causing it to operate improperly - but the relay is most likely. Good luck.

 

[morgfarm1]

Just an update here..

One of my mechanics thinks that the symptoms I mentioned ( Along with what he saw on a set of AC gauges) that the Drier/accumulator might be full of moisture. Money isn't an option right now, and with the blend doors out, Not gona be even useful to fix yet, but it gives me a goal for next summer. thanks for the feedback.

 

[masospaghetti]

The drier could be full of moisture but that wouldn't have any effect on your symptoms. Diagnose the relay first.

One thing to watch for: The low pressure side of the a/c system will see lower pressures with higher RPMs because the compressor pump is running faster. It's possible you have a low refrigerant charge and when you accelerate hard, the higher RPMs are causing pressures to fall on the low side below the cutoff.

Does this happen in PARK if you just rev up the engine a little bit? Does vehicle speed affect it at all? Vehicle speed would indicate an issue with line pressure as well, since a fast moving vehicle causes the condenser to be more effective and therefore lower line pressure.

 

[my98nnj]

The dryer doesn't get full of moisture over time, it's a sealed system. Unless it's been opened several times and major components replaced, the dryer is fine.

 

[morgfarm1]

Does this happen in PARK if you just rev up the engine a little bit? Does vehicle speed affect it at all? Vehicle speed would indicate an issue with line pressure as well, since a fast moving vehicle causes the condenser to be more effective and therefore lower line pressure.

It happens at any state the vehicle is in -- park or moving.

As tested, leaving the vehicle parked and revving the engine to 2500 (which is about where it'd be doing 70 down the freeway) the compressor has been seen cutting out. Once the RPMs go back down, the compressor kicks on. I'll need to test a bit more once I find ways to correct the blend door, but the last test had the compressor kicking on and off even at an idle, windows down on a 90 degree day and the climate control set to 60.

I'm obviously not an AC System expert, so any and all feedback will be taken here. I know the power of the minds here at this forum so I can pretty much work with anything you guys throw at me.

@my98nnj: It's a used vehicle, no idea how many times the system has been accessed, if at all.
I do know i added SOME refrigerant to it when I first tried to run Air, but it didn't do much I don't think. (Probably because the AC Clutch kept kicking in and out)

 

[morgfarm1]

OOOK, So I think we found the culprit. Blend Doors.

When I went to troubleshoot what I thought to be charging system issues, I disconnected the battery while doing so. When I gave power back to it, and ran the truck, I could hear this annoying knocking coming from behind the glove compartment.

I stick my arm back there onto the black box behind the glove box, and felt the knock coming from there. Having heard of a 'Blend Door' issue in these, I assumed that's what it would be. My mechanic had be disconnect the power to that area, and, i'll be dipped if I don't have a decently working A/C now. Not 100% perfect, but it's worked fine the last 2 days with temperatures falling this side of 100.

New problem: Fixing that don't look fun. I have another thread that gave suggestions on that, and I don't liek it Thanks Guys!