a/c compressor stalling
 

What will cause the a/c compressor to stall? It has always been a problem, but as long as I run the fan on low it seems to work. However I flushed the system this spring, and recharged with enviro safe 12a. Real cold air now 34 degrees. After about an hour of highway driveing the compressor stalled. Could smell the clutch so turned if off. pulled over, could turn the compressor so it did not lock up. I am assuming there was just to much load on it, but why?

Does it ever cycle off? And it sounds as if the clutch is going/gone bad if you smelled it and you can spin it by hand easy.

Too much head pressure. Check your fan clutch. If your fan isn't working well enough, the system will over pressurize and lock the compressor. If your fan is OK, just let a little R12 out until it doesn't do it any more.

Are you sure you werent smelling the belt slipping around the pulley?

Charge weight is critical. Too much and you'll slug liquid...and the Sanden compressor in my 91.5 was about the cheesiest, most fragile design of any automotive a/c compressor I've ever had apart. Also, make sure you have the RIGHT amount of the RIGHT oil for the refrigerant type.

My 93 has never ran that cold you must have put a lot of freon in it my truck only run at 45 degrees but it has never been charged sence it was new.Thinking you have to much pressure??

Did you add a/c oil when you flushed it?

I have the same issue... I charged mine with freeze12 and it says to use 10% less freeze12 than r12. I'm @36oz and my truck says 38oz. Not sure 1.8oz would do it? My oil was measured in so I know it wasn't that.

I think I put 32ozs in. Did not write it down, wish I had. It is a bit cool (about 60degrees outside)to test pressures right now, maybe later this week when it warms up I can can run some tests. It seems like overfilling is the general consenses.

Will I be able to tell if it is overcharged by the suction, and discharge pressure? our do I need to evacuate, and weight the charge? If I evacuate does the oil charge get messed up? I do have a recovery machine, and a recovery tank.

what are the pressures after the system has run for 5 min or so? should be in the neighborhood of 30-ish on the low and 200-250 high, but the high side will/should be more dependent on the ambient temp and the amount of airflow thru the condenser.

High head pressure is the problem. As was said earlier, a high head pressure basically means liquid is ran through the compressor. Since you can't compress liquid it stalls out. If you put 32 ounces in , you likely are over filled.

High head can be caused by several factors, over charge just one of them. They are over charge, bad expansion valve and air flow across the condensing coil. Two thing to always do, wash the evaporator out very well every year. I use engine cleaner followed by dawn dish soap, it works well and theres no oily residue to collect more dirt. You can also buy a coil cleaner that foams from most A/C places, just don't let it get on the paint. Bugs, road grime and dirt reduce the flow. You cant really diagnose a problem until simple stuff is removed. Second, even with a good clutch fan the air flow across the coil at idle is very low, to help get a better reading set a box fan in front of the radiator while your checking pressures.

I'm not sure of brand of refrigerant you put in but as a rule most run between 35% to 40% of the original in weight.

Now that you mention cleaning the condenser, it has been a while, will do so. I did replace the trans cooler after a rock hit with a generic unit, and it is in front of the condenser now. perhaps this is dumping to much heat to the condenser. Had not thought of that. Next warm day will check everything.

By the way no fan clutch, it is a direct drive with a flex fan.

I moved the trans cooler under the bed. It had been leaking just a little so made a very oily mess of the a/c condenser, and was covering about 1/3 of it.

a/c pressures is about 200-210 on the high side 80 degree outside temp. By the way looks like I put 16 oz in of enviro safe r-12a. Counted used cans in the trash. Used their oil. Vent temp on low fan dropped to 10 degrees, low 30's with fan on high.

Have not driven with the air on for any amount of time to see if moving the trans cooler and cleaning has cured it yet.

High pressure will drop as cab cools off as well. Cleaning is very important, we all over look it at times.