A/C cycles on off constantly

bert32068 · 09-21-2008, 03:59 AM

004 Forester ac blows ice cold then compressor cuts off then back on all within 10 secs. This is a continous process.Pressures are fine,refrigerant is full. any ideas? thx

adc · 09-21-2008, 05:03 AM

If it is indeed cycling too much. Its either cycling on LP cutout or high pressure cutout.

If its cycling on High Pressure it means that you are overcharged or the heat load is too high or a combination of both.

I suspect that you are going out on low pressure cycling. Try changing the filter and then just to see what's going on..operate the fan on a higher setting in combination with adding a bit of heat. That will keep the pressures up a bit.

Other than that..possibly a low or high pressure switch is defective.

scubadoober · 09-21-2008, 05:21 AM

Is this with the climate control on? Does this happen immediately after turning on the A/C or is it after it has been running for a few minutes?

bert32068 · 09-21-2008, 12:41 PM

Quote:

Originally Posted by scubadoober

Is this with the climate control on? Does this happen immediately after turning on the A/C or is it after it has been running for a few minutes?

With climate control on or off. Yes it takes a couple of minutes to start the process but then continues.

Sylvia · 09-21-2008, 04:11 PM

The a/c system cycles to control low side pressure. It shuts off at about 20 psi (low). If it didn't cycle, the evaporator would freeze and no air would get through. The fact that it is cycling suggests to me that it is working as designed. If it didn't cycle it's either REALLY hot outside or the system is undercharged.

bert32068 · 09-21-2008, 04:16 PM

Quote:

Originally Posted by Sylvia

The a/c system cycles to control low side pressure. It shuts off at about 20 psi (low). If it didn't cycle, the evaporator would freeze and no air would get through. The fact that it is cycling suggests to me that it is working as designed. If it didn't cycle it's either REALLY hot outside or the system is undercharged.

You are correct but this cycling is so often that the system blows cold air and then not which doesnt let the car cool down at all.

Tau137 · 09-21-2008, 07:06 PM

Quote:

Originally Posted by bert32068

You are correct but this cycling is so often that the system blows cold air and then not which doesnt let the car cool down at all.

How frequent is the cycling, anyway? If you get some cold air (i.e., frequency is very low, it doe work for a some time before switching off), it might be not the AC system itself but the climate control (electronics/sensors) issues.

bert32068 · 09-22-2008, 12:55 AM

Quote:

Originally Posted by Tau137

How frequent is the cycling, anyway? If you get some cold air (i.e., frequency is very low, it doe work for a some time before switching off), it might be not the AC system itself but the climate control (electronics/sensors) issues.

My thought exactly, Im thinking that temp sensor in cabin is malf but wanted to know if any one else had same prob before spending money.

adc · 09-24-2008, 02:44 PM

Quote:

Originally Posted by bert32068

You are correct but this cycling is so often that the system blows cold air and then not which doesnt let the car cool down at all.

Could be low in pressure.

09-21-2008, 03:59 AM	#1 (permalink)
bert32068 Join Date: Sep 2008 Location: florida Posts: 4 Gallery: 0 Feedback Score: 0 reviews	A/C cycles on off constantly 004 Forester ac blows ice cold then compressor cuts off then back on all within 10 secs. This is a continous process.Pressures are fine,refrigerant is full. any ideas? thx

09-21-2008, 05:03 AM	#2 (permalink)
adc Contributing Member Join Date: Aug 2007 Location: Elizabethtown, Pa. Posts: 3,214 Gallery: 82 Feedback Score: 0 reviews	If it is indeed cycling too much. Its either cycling on LP cutout or high pressure cutout. If its cycling on High Pressure it means that you are overcharged or the heat load is too high or a combination of both. I suspect that you are going out on low pressure cycling. Try changing the filter and then just to see what's going on..operate the fan on a higher setting in combination with adding a bit of heat. That will keep the pressures up a bit. Other than that..possibly a low or high pressure switch is defective. __________________ Be careful what you wish for.

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09-21-2008, 05:21 AM	#3 (permalink)
scubadoober Join Date: May 2008 Location: Nashville Posts: 1,475 Gallery: 0 Feedback Score: 4 reviews	Is this with the climate control on? Does this happen immediately after turning on the A/C or is it after it has been running for a few minutes?

09-21-2008, 04:11 PM	#5 (permalink)
Sylvia Join Date: Mar 2008 Location: San Jose, CA Posts: 85 Gallery: 0 Feedback Score: 0 reviews	The a/c system cycles to control low side pressure. It shuts off at about 20 psi (low). If it didn't cycle, the evaporator would freeze and no air would get through. The fact that it is cycling suggests to me that it is working as designed. If it didn't cycle it's either REALLY hot outside or the system is undercharged.