AC Compressor short cycling even with the heat on.

[revhardSHO]

Strange problem. With the climate control on and set to any setting (including 90* heat) the AC compressor will short cycle for about 4-5 seconds then disengauge for about 25-30 seconds and then repeat the above. The compressor sounds normal but doesnt stay on long enough for me to see if the AC system is working. Strange part about it is it will cycle like this even if I have the heat blasting. Im sure its terrible for the ac clutch so I would like to get it fixed ASAP. For now I just leave the climate control off. Im thinking the system is running low on refridgerant, but thats just an uneducated guess. Any brands to stay away from or is it all good? Should I run a bottle of stop leak in there too? Why on earth is the compressor cycling when the heat is on??? Any thoughts?

thanks!
Silas

 

[Mr Anonymous]

First thing you'll want to do it put a gauge on the low side and see what you have for pressure. Short-cycling is usually due to a low charge.

The A/C compressor will generally cycle in all settings except off, vent, and floor above a certain temp (~50 deg. F IIRC), this is to remove moisture from the air.

 

[revhardSHO]

First thing you'll want to do it put a gauge on the low side and see what you have for pressure. Short-cycling is usually due to a low charge.

The A/C compressor will generally cycle in all settings except off, vent, and floor above a certain temp (~50 deg. F IIRC), this is to remove moisture from the air.

Thanks. The low pressure port is on the ac line near the BARO sensor and above the computer? I assume I can buy a gauge at AZ?

edit: If it does need a recharge what pressure do you recommend for optimal effiecency? At what pressure will the compressor begin to short cycle?

 

[rangerj]

Put the A/C on and see if it short cycles. If it does it is usually a sign of low pressure, which indicates a low refrigerant charge.

An A/C system is a sealed system so that the only way the system can get low is for there to be a leak. Your 94 I assume uses R-134a refrigerant, which is relatively inexpensive. You can add a charge of refrigerant that has a small amount of oil and a conditioner, and hope that the charge holds.

The chemical compound "R-134a" should be the same no matter what the brand name is on the can. You can get it a Auto Zone, or Wall Mart. rangerj

 

[revhardSHO]

Put the A/C on and see if it short cycles. If it does it is usually a sign of low pressure, which indicates a low refrigerant charge.

An A/C system is a sealed system so that the only way the system can get low is for there to be a leak. Your 94 I assume uses R-134a refrigerant, which is relatively inexpensive. You can add a charge of refrigerant that has a small amount of oil and a conditioner, and hope that the charge holds.

The chemical compound "R-134a" should be the same no matter what the brand name is on the can. You can get it a Auto Zone, or Wall Mart. rangerj

Cool (no pun intended)
Yes it does short cycle with the A/C setting on.
From service records the vehicle had the AC system checked out at about 100K. System was recharged, IIRC. Does stop leak work well? Maybe I will try that too if the system does not hold a charge.