95 Camry AC comes on for awhile, then compressor shuts down.

[lhiga]

Could it be low on freon?

[ACProf]

How long is "awhile"?

After it shuts down, what do you have to do to get it to come on again?

Could be a low R-134 situation, but depends on answer to first question. What are the low and high side pressures when it is running? If it isn't low and you charge in more refrigerant anyway, you'll increase the level , complexity, and costs of repairing the system.

Could be worn and pitted contacts on the AC Compressor Relay.

Could be the clutch gap is worn too wide and the clutch is dropping out when it gets hot. When the AC stops, while the engine is still running, tap the front of the pulley clutch toward the compressor and see if momentarily re-engages.

Could be a slow or stopped condenser cooling fan motor(s), causing the condenser to overheat and the high pressure to go up with it and trip out the high pressure sensor.

Does the system cool adequately when it is running right?

ACProf

[lhiga]

For the questions asked:
1. When we went out to retest this system it did not shut down. The system kept running.
The compressor was turning but there was no cooling.

2. "How long is "awhile"." approx.30 minutes.

3. "What are the low and high side pressures when it is running?" Low 40-50psi, High=??? When cooling stops low side pressure drops to zero psi.

4. "Could be a slow or stopped condensor cooling fan motor(s), causing the condensor to overheat and high pressure to go up with it and trip out the high pressure sensor." Low pressure slowly decreased as time elapsed. Down to 25 psi after driving a mile.

[ACProf]

3. "What are the low and high side pressures when it is running?" Low 40-50psi, High=??? When cooling stops low side pressure drops to zero psi.

Low side is too high for any real cooling to occur. Should be 25-30 when the compressor is engaged. High side pressure reading will confirm if its a charge problem or something else. Autozone will lend you a manifold guage set for a holding deposit. Compressor needs to be engaged when taking pressure readings. If the clutch hub isn't turning the pressure readings won't mean much.

4. "Could be a slow or stopped condensor cooling fan motor(s), causing the condensor to overheat and high pressure to go up with it and trip out the high pressure sensor." Low pressure slowly decreased as time elapsed. Down to 25 psi after driving a mile.

"Down to 25 psi" is a good thing. It means the evaporator is cooling down which reduces the pressure. UNfortunately, when it gets LOWER than this (a sign of a possible undercharge) the automatic system will cut out the compressor to prevent the evaporator from icing up. This WILL cause the low side pressure to drop to ZERO until the compressor cuts back on.

GET THE GUAGES. Report the pressures here. There are people here who can then direct on the PROPER course for repair.

DON"T ADD ANY CHARGE WITH "LEAK STOP" or "SEAL CONDITIONER" unless you're prepared for a complete rebuild down the road!

ACProf

[lhiga]

"Low side is too high for any real cooling to occur. Should be 25-30 when the compressor is engaged. High side pressure reading will confirm if its a charge problem or something else. Autozone will lend you a manifold guage set for a holding deposit. Compressor needs to be engaged when taking pressure readings. If the clutch hub isn't turning the pressure readings won't mean much."

When I first turn the AC on hi=250, lo=56. After 20 minutes hi=290, lo=50. After 30-35 minutes hi=250-290, lo=0. NOTE: The compressor is still running(engaged) but no flow indication on the dryer(sight glass). Air in the vehicle is warm.

[cm5400]

When I first turn the AC on hi=250, lo=56. After 20 minutes hi=290, lo=50. After 30-35 minutes hi=250-290, lo=0. NOTE: The compressor is still running(engaged) but no flow indication on the dryer(sight glass). Air in the vehicle is warm.

With high side that high and low side in vacuum, you have a blockage somewhere preventing the refrigerant from returning. Check to make sure that the expansion device (o-tube or txv) is functioning properly.

[lhiga]

Could it be moisture in the lines freezing when the AC is running then defrosting when the system ain't running. This would seem to explain the symptoms better. How do you check an expansion valve?

[Tom Greenleaf]

Moisture CAN cause erratic reading for sure but what opportunity did any have to be introduced?

Any expansion device should be warm before it and cool/cold after it. If same on both sides there indicated an problem there,

T

PS: A shot at a fix could be to evacuate this system and meticulously recharge to exact spec/weight of charge. Leave in vacuum state for as long as you can - hours if practical....