A/C Compressor Doesn't Cycle Just stays On

[b_f_c_99]

Hello I have a 92 XLT R-12. My compressor turns on just fine, but it
doesnty cycle at all, just stays on until it overheats (I think) then it shuts
off. The yellow light on the control knob stays on. If you toggle the control
off, wait a few minutes and turn it back on the compressor starts back up
and everything is fine, for a while then it shuts off. When I aquired the vehicle
4 years ago the A/C was doing this so I had it recharged and serviced but the
problem persisted. Any ideas?

Greg

[Jason94sport]

Bad pressure switch. It's the thing that is screwed into the dryier. Should have an connector on it.
Or
Bad blower motor relay. It's in the fuse box under the hood.

[b_f_c_99]

Thanks you for the info! Where is the pressure switch? Will the system have
to be discharged or is it just something that pops off and on? Thanks for the
reply, this problem has been ongoing for 4 years and my wife is really sick of it
BTW all the fan speeds work fine, could it still be the relay?

[shamaal]

Greg[/quote]

Originally Posted by b_f_c_99

Hello I have a 92 XLT R-12. My compressor turns on just fine, but it
doesnty cycle at all, just stays on until it overheats (I think) then it shuts
off. The yellow light on the control knob stays on. If you toggle the control
off, wait a few minutes and turn it back on the compressor starts back up
and everything is fine, for a while then it shuts off. When I aquired the vehicle
4 years ago the A/C was doing this so I had it recharged and serviced but the
problem persisted. Any ideas?

Greg

From the description, I'm a little confused about whether it shuts off or not, The first question is: Is it cooling?

The pressure switch is located on the accumulator on the passenger side, just below the LP service port. It is visible behind the tube in the picture. It screws on and off hand tight; no discharge required.

The compressor clutch should come on at start up. It will run until the the pressure drops from the compression of the refrigerant gas. When it stops the pressure begins to equalize until it rises sufficiently to turn on the clutch again. There should be a corresponding idle change. The amount of time the clutch engages is dependant upon a number of factors including ambient air, amount of charge and heat removal from condensor. On a hot day (+90F) in my driveway the compressor does not cycle off. As soon as I start moving it begins to cycle. At 93F ambient I draw 45F at my vents on the highway. The yellow light and switch indicates that you want A/C, it remains on as long as the switch is on; it does not indicate A/C clutch engaged or disengaged.

If there is a problem, the switch could be bad, the system could be overcharged, or there could be a blockage. The first step is determining whether it's blowing cold air.

I note that you say it is an R12 system, R12 is difficult to get, should the system have to be opened for repair.

I draw your attention to the stickies at the top of the page, feel free to ask questions.

[Turdle]

I just happen to have a pressure switch off a 97, if it will work it's yours
Just hook me up with a spot to catch a nice rainbow.

[b_f_c_99]

Shamaal, yes I get cold air, and the fan works at all speeds, the idle changes when the
compressor engages. BUT, you can be driving along highway, intown or just idle at a stop
light doesnt really matter. You hear the compressor switch off and then it never comes
back on, well on occassion it turns back on by itself but it is rare. I've driven around
for over a half hour without it coming back on. BUT if you toggle the switch to off,
wait a few minutes and toggle it back on, you hear the compressor click and everything starts running fine again. There is no real timing pattern to when it kicks off, seems to happen faster the hotter it is. I found the switch, it is all of a $10 part
and it just unscrews? Clockwise or counter?

PS: JT you can't hardly NOT catch fish around Missoula or the Bitterrot valley...

[b_f_c_99]

Sorry another thing, I almost never see anywater puddles from this vehicle. Normally
wouldn't there typically be a puddle of water if it was just sitting at idle in your driveway?

[Jason94sport]

Does air stop blowing from the vents when it happens? The fan will still work & your hear it going but little or no air comes from the vents?
Cause I had that problem after the X was driven for a while. A new pressure switch fixed it.
It unscrews counter clockwise as normal.

[b_f_c_99]

The air continues to blow like normal, it really acts as if you just toggled it off.
There is no difference on any of the panel settings either MAX A/C - Panel Floor ect.
All the fan and panel settings work correctly whether the air is off or on.
I'm starting to wonder if the problem isn't the switch itself. Could the compressor
cycle like normal but the switch just not be sending a signal to turn the
compressor back on? Or could the system be overcharged and the pressure gets to high and the system shuts down? If that was the case wouldn't it turn
back on itself when the pressure fell? It does occassionaly turn itself back on
but in most of the time you have to toggle the switch off, wait a few minutes
and toggle it back on. If you just toggle the switch off and then back on without any wait it doesnt restart the compressor.

Greg

[shamaal]

FWIW, The switch is normally open at or below 24.5 psi; it is normally closed at or above 43.5. There is no high pressure cutout switch. There is a high pressure relief valve on the refrigerant line manifold, but that's not a nominal use.
The switch just unscrews anticlockwise.
I understand what you are saying now, I must have been dense before.

Another likely possibility is a low charge, it takes longer and longer for pressure to build up high enough to trip the A/C clutch on switch. Lack of condensate from evaporator, could signal a clogged evaporator drain or not enough cooling to cause condensation.

Electrically there is the console switch, the pressure switch, and the WOT switch. and connecting wires.

[b_f_c_99]

Ok, I started thinking about possible wiring issues, so I unplugged the
wiring on the compressor took a look at the connections, no problem that I
could see, plugged it back in. Pulled the connection of the pressure switch
was kinda a pain to get off but it came. Couldnt see any corrosion ect, plugged
it back in. Now the compressor cycles off and on just fine. When you first
turn on the AC you can hear it cycle off and on about every 5 to 8 seconds.
After a couple miles of driving this increases to every 15 to 20 seconds.
Bad connection? Wiring breaking down and I just happened to jiggle it around
so it works? I guess time will tell. If you have any other thoughts throw em
at me!!!

Greg

[shamaal]

Perhaps sticky switch?

[b_f_c_99]

So i messed around with the wiring again and the AC problem returned.
So I unplugged the wiring again and now it works correctly. Still might
be the pressure switch, the one that screws into the collector box right.
(your picture is kinda dark shamaal) If its the one I'm thinking of it screws into
the condesator/collector has a white maybe 1/2 hex bolt lokking thing on the screw in end? IF so are you SURE you can just unscrew it without losing the
refrigerant? Is there some sort of compression fitting that seals it off? The
people at the NAPA place seem to think it will discharge, but I'm more inclined
to believe the people that actually own explorers and know something about them.

Greg

[shamaal]

A better picture from the side and top of the accumulator and the switch. Yes, you can unscrew the switch, use the hex nut. The accumulator has a schrader valve at this port. There may be a short sputter, but you won't lose any freon
Remember it's plastic, so no excessive bearing down when tightening.
If the NAPA place wishes to expand their horizon, they can pull and look at a replacement accumulator to satisfy themselves. This is not a dig at the stores, there are literally thousands of car parts and configurations, but they have the resources to check.

[b_f_c_99]

Thanks shamaal, this was the switch I though you were talking about the
first time, thanks for the updated pic and info. I'm probably going to take
taht out and put a new one in. I'm pretty sure either the wiring is goofy there
or the connection. I appreciate all the info and help!!
Greg

[HardTech]

Had this happen on mine after getting the system fully redone after my compressor went out. Nothing like spending 300 bucks and it pulls the im on and cold, shut off to cycle and never comes back. In a 110 degree heat my truck almost found its way to a junk yard it ticked me off so bad.

But in the end it was a $5 part. Just screws off, and then you screw the new one on. unless what stops the A/C from coming out is bad, is should work the same as a tire. The quicker you get it off, the less chance it has to lose pressure, same for putting it on. It was a quick 10 mins fix inlcuding getting the part.

So good luck to ya, its just amazing the vital parts of our cars are up to a $5 part. Gotta love pressure sensors and T-Stats... both quit for a $5 part and leave you in heeps of problems :P

[b_f_c_99]

I dropped the 92 off at the A/C shop this morning and they tracked down
the problem to a bad clutch on the compressor. We'll see if they are right.
I still think it could be the wiring. I'll post results in a couple of days and
100 plus degrees here in Montana.

Greg

[HardTech]

I dont know, before ya droped it off a quick was to test it is the connect the wires that pluged into the switch. If it turned on every time it was the switch or low pressure. but if it came on in the first place when you started it up and just didnt work when it cycled than the pressure would have been fine.

I hope you trust them, a paper clip would have confirmed if the part was bad or not.

[b_f_c_99]

HardTech the ability for the compressor to come on wasn't the problem. It
just never cycled off and on properly, and eventually it would just cycle off
and the only way to get it to come back on was to toggle the A/C switch off,
wait for a few minutes and toggle it back on. The mechanic that replaced the
clutch said that the coil inside the clutch was just hosed and it couldnt' create
enough magnetic pull to rengage the clutch. He further explained that heat
tends to magnify the problem. And so far I'd have to agree with him because
it has worked just fine since. If anything else goes crappy i'll post.
Thanks for all the help and suggestions from everyone!

Greg

[CEO]

Originally Posted by b_f_c_99

Hello I have a 92 XLT R-12. My compressor turns on just fine, but it
doesnty cycle at all, just stays on until it overheats (I think) then it shuts
off. The yellow light on the control knob stays on. If you toggle the control
off, wait a few minutes and turn it back on the compressor starts back up
and everything is fine, for a while then it shuts off. When I aquired the vehicle
4 years ago the A/C was doing this so I had it recharged and serviced but the
problem persisted. Any ideas?

Greg