A/C Compressor always running (not cycling off)

[Greg Gibbs]

I'm having an A/C issue with my 2002 Explorer Sport Trac 4x2 with 153K miles. I've read lots of posts about A/C issue, but nothing quite like my symptoms.

My A/C works normally most of the time, but will occasionally blow warm air when I'm in stop-and-go traffic or after idling for a few minutes. When I get back up to speed, it seems to operate normally. I had similar symptoms a couple years ago and a local shop added some refrigerant, which helped. This time, I bought a can of A/C Pro with the gauge with plans to add refrigerant myself. According to the can's gauge, it was within tolerance, but on the lower side. I added a little refrigerant (not very much), but it did not fix the problem.

The engine has never overheated and the engine temp gauge doesn't indicate any issues (stays left of center between C and H at operating temp). I've also replaced the fan clutch and water pump recently, along with the radiator cap.

While troubleshooting today, I noticed that the A/C compressor clutch is ALWAYS engaged when the A/C is on. (Most people have the opposite problem.) I'm accustomed to it cycling on and off with a loud clicking noise, but it currently doesn't turn off unless I turn the A/C to the off setting. (It also turned off when I pulled the A/C compressor relay as a test.) Since it was cheap, I installed a new A/C clutch cycle switch ($13) on the accumulator, but nothing changed.

I'm guessing the answer is to have it serviced by an A/C shop, but I'd like to know what could be causing this. Compressor clutch/coil? Expansion valve/orifice tube? Any other ideas?

Thanks guys!
Greg

 

[EddieS'04]

While troubleshooting today, I noticed that the A/C compressor clutch is ALWAYS engaged when the A/C is on. (Most people have the opposite problem.) I'm accustomed to it cycling on and off with a loud clicking noise, but it currently doesn't turn off unless I turn the A/C to the off setting. (It also turned off when I pulled the A/C compressor relay as a test.) Since it was cheap, I installed a new A/C clutch cycle switch ($13) on the accumulator, but nothing changed.

When my AC is on the compressor runs all the time, normal in the summer. The switch on the accumulator is to take the compressor out if you are low on freon, as so the compressor doesnt' get damaged. lack of enough freon flow will not carry enough oil thru for lubrication. The compressor will cyle momentarly with AC off our even with heater to keep the system lubed.
I dont see a problem. After replacing the switch did you pull a vaccum on the system before recharge? Ambient air in the system will create moisture. Moisture and freon creates hydrocloric acid and destroys the system from the inside.

 

[Greg Gibbs]

Even in summer, I thought the compressor should cycle on/off every few seconds. I can't recall it ever running constantly and never cycling off. Also, the tube from the accumulator to the compressor has condensation on it and creates a pool of water under the truck. I've never noticed that before. It usually drips only from the evap tube area.

Regarding that clutch cycle switch, I assumed (after a quick Google search) that it would have a Schrader valve to prevent loss of refrigerant during removal/replacement. I was surprised when it started hissing (leaking) when I took it off, so I just replaced the O-ring and put the new switch on as fast as I could. Afterwards, I checked the low-side pressure with the gauge on the can of A/C Pro and it still indicated that the pressure was good. (I realize opening the system is not good.)

Assuming the compressor clutch should remain engaged all the time, any other ideas as to why my A/C blows warm air after idling?

 

[EddieS'04]

I checked the low-side pressure with the gauge on the can of A/C Pro and it still indicated that the pressure was good. (I realize opening the system is not good.)

Assuming the compressor clutch should remain engaged all the time, any other ideas as to why my A/C blows warm air after idling?

If it starts cooling good while reved to 1500rpms. It might still be low.???IDK...Find something to put in the throttle stop, to hold about 1500rpms. Then take a low pressure reading. "Do not adjust the throttle stop". That would screw with the ECU idle control.

I have seen the gauges on the cans not read right. Try bringing the pressure up the border of good and too high. Dont go over. If you have a thermometer put it in the center vents. While on max air, high fan. Look for it to get to at least 45 to 50 degree's.
If it was still bleeding freon while you replaced the switch. You are probably ok. If you cant solve this. You need someone that has the gauge set to read the high and low side. To do a complete trouble shoot of what the system is doing. Your Trac is older than mine.
I See your located in a hot zone same as me. Im in the Houston area. Hot and humid. Ac's are working over time already. I hate to see august.

 

[Phill R]

Check the fan clutch spring. I had one with a bad spring and the fan clutch would not lock in and cool. I spun it to always engaged and it was better after that

 

[Greg Gibbs]

I replaced the fan clutch and water pump a few weeks ago. I was hoping it would solve this issue, but I figured it needed to be done either way at 153k miles. Unfortunately, it didn’t help.

How do you spin and lock it as you mentioned?

 

[Phill R]

This I did on my Bronco 2. The spring pulled off the front of the clutch and I turned the center stem about a half turn and put it back on. When I revved the engine after that, you could hear the difference in the fan pushing more air.

 

[Greg Gibbs]

I'm going to inspect the a/c compressor clutch tonight and see if the air gap is correct. I know that usually the air gap increases over time and prevents the clutch from engaging, which can be corrected by removing a spacer or two. Wondering if my clutch has the opposite problem. I feel certain that the compressor's clutch should cycle it on and off every few seconds and mine just stays engaged (compressor running) all the time.

 

[Greg Gibbs]

Didn't get a chance to check the air gap, but I did some other minor troubleshooting. (I know it's all guess work unless I hook up some gauges or take it to a shop for inspection.)

1. While driving today to and from work, I listened to the A/C compressor and could hear the clutch engage/disengage periodically as expected. Air was blowing cold as long as the truck was moving. When idling at a stop light, the compressor never cycled off and the air was not quite as cold. I also tested it while idling/parked and it would only cycle off/on if I revved the engine to 1500RPMs or so. At idle, the compressor runs constantly and never cycles off. Occasionally, in stop-and-go traffic, the A/C starts blowing hot/humid air. I suspect the compressor is overheating from running too long and finally shuts off for a while.

2. I tested the compressor clutch by turning the ignition to the ON position (engine not running) and turned the A/C switch back forth from on to off listening for the A/C clutch clicking noise. I can hear the A/C relay clicking, but the clutch does not move and appears to be engaged (meaning the compressor would be running if the engine was running). I've watched several troubleshooting videos where the clutch should engage/disengage in this test. (Anyone willing to do that quick test to see if their Gen1 Trac does the same?)

3. I intended to get a voltage reading to make sure the coil is getting power, but the pins on my multimeter were too big to fit in the connector. I also wanted to test the coil's resistance, but couldn't access the connectors. I think I'll need to remove the driver side front tire to access the compressor connector more easily.

Based on what I've found, I'm wondering if this indicates that the clutch/coil is not working properly and should be replaced. (Autozone has the clutch/pulley/coil kit for $83.)

I *think* the refrigerant level is good, but that probably still need to be checked to be sure. The only other thing I can think of is that the orifice tube may be clogged. I've owned the truck since new and it hasn't been replaced. Any one have another suggestion?

 

[Todd Z]

Re do the engine off key test, this time try spinning the front pulley by hand and see if it is truly engaged.... then you will know if it was locked in.....
You may have a low or high pressure switch going bad, air in the system, clogged orifice tube or bad clutch coil......

 

[Greg Gibbs]

Removed the belt and re-did the test. A/C compressor pulley spins freely in both cases (ignition on, A/C switched on and off). Is that expected behavior? I'm assuming the clutch should lock when ignition is on and A/C is switched on. (I still need to verify that I actually do have power at the coil.)

 

[EddieS'04]

I dont think the clutch will lock, until the motor is running for 6 seconds. Controled by the ECU...

 

[Todd Z]

Eddie is correct, the engine must be running.

 

[Greg Gibbs]

Reviving this old thread with an update. My problem turned out to be a slipping clutch on the compressor. I removed one spacer (it was the only one in there) to reduce the gap and now my A/C works great. NOTE: This is the original A/C compressor on my 2002 ST (169K miles).

 

[Todd Z]

Great update. Thanks.

 

[Tylerxp2]

Reviving this old thread with an update. My problem turned out to be a slipping clutch on the compressor. I removed one spacer (it was the only one in there) to reduce the gap and now my A/C works great. NOTE: This is the original A/C compressor on my 2002 ST (169K miles).

Mine runs most of the time as well, when it cycles off it siunds like a simi's compressor when the tanks full. Big whoosh sound.