A/C cycles on and off

[jmden]

Hi,

I've got a 1997 Explorer that we purchased with 18k on it. Anytime the temps are above 70F or so and the a/c is on and I'm stopped at idle, the a/c compressor is constantly cycling on and off about ever 6-7 seconds or so. This only happens in the above specific conditions. If the a/c is on and it's 60F, the pump won't cycle. If we are using just defrost any time of year, the pump won't cycle like this. It's very specific conditions as to when it constantly cycles.

This rig has been at the dealership for this many times. One time we left it there for a week. It was left with an a/c specialist shop for a few days at one point as well. Didn't change a thing.

Could it be that I'm low on coolant? This would take 134a, right?

Thanks for any ideas,

Jon

 

[my98nnj]

The compressor will run when it's above freezing on any setting except vent and floor.
The compressor will cycle to maintain evaporator temperature. That's normal operation.
The reason for running the compressor is to dehumidify the air coming into the cabin.
Excessive cycling may indicate a low refrigerant level.

If you think it's cycling excessively and doesn't seem to cool properly in the summer, then chances are the charge is low. If it's cooling nicely, then it's operating normally.

 

[jmden]

The compressor will run when it's above freezing on any setting except vent and floor.
The compressor will cycle to maintain evaporator temperature. That's normal operation.
The reason for running the compressor is to dehumidify the air coming into the cabin.
Excessive cycling may indicate a low refrigerant level.

If you think it's cycling excessively and doesn't seem to cool properly in the summer, then chances are the charge is low. If it's cooling nicely, then it's operating normally.

The a/c system does seem to cool properly in summer, but I have never heard or witnessed a vehicle's compressor cycling this often. Probably every five seconds, now that I think about it, and this occurs continuously while at a stoplight until the vehicle starts moving again or the a/c is turned off. People around the Explorer, even folks in other cars, start to look at the car like something is wrong it is so obviously noticeable and loud when the a/c compressor cycles on and off every 5 seconds. This is not normal.

Any other Explorer owners here that have this happen to them or any of their other vehicles and consider it normal?

 

[jmden]

http://www.doityourself.com/stry/what-to-do-when-car-ac-compressor-cycles-on-and-off#b

Talks about a bad computer being the problem...

Or, a pressure switch? This guy is having similar problems to as my vehicle, but in a differnent way--fast cycling when the car is moving and the problem didn't change after a service:

http://www.justanswer.com/subaru/2eozc-air-conditioner-fully-charged-short-cycles.html

Or, overfilled:

http://www.bsntech.com/bsntech-blog...ycling-on-and-off-in-car-air-conditioner.html

 

[deweyville65]

Is the engine fan coming on. If not, there is not enough air coming through the condenser at idle, the condenser is getting hot, causing high pressure and cycling the compressor. Just a thought, because the cycling goes away at speed, correct? Or maybe it is cycling at speed, and you just do not notice it? In that case, I would bet on low refrigerant, and yes, R134A.

 

[Dave 1955]

18k for miles..dang that's low!

 

[koda2000]

18k for miles..dang that's low!

i think he's saying it had 18k on it when they bought it. not now.

 

[1992fordgreen]

18k...i was gonna say...

 

[jmden]

Well...after cleaning the idle air control valve and the mass air flow sensor (my guess is the main culprit was a dirty idle air control valve as idle was when the annoyance occurred), so far this summer this annoying cycling of the AC on and off in warm temps while at idle has not occured! Simple fix or what? As mentioned before, this rig has been at the dealer several times to try and figure this out to no avail. It's also been to an AC shop for days to no avail. 20 minutes of cleaning the idle air control valve. Who knew? Thank the Lord, this rig is running better than it ever has with 190K on it...