Air Conditioning - AC compressor overheats and no cool air

I have a Janitrol AC unit (about 8 years old, not sure of tonnage, it's not a heat pump - I have gas heat) which runs for about an hour and then trips the overload. With a clamp-on, I measured it drawing only 5-6 Amps. Also, when the unit DOES run, the air coming from the registers is not really cool. Is it possible that the overload is due to a lack of freon? I figure if it was binding mechanically, it would draw more current, right? The motor and compressor are the same unit (as I guess most are). When it runs, the "piping" FROM the house is hot and the piping going TO the house is relatively cool. I'm thinking that the compressor is liquid cooled and the lack of freon is why the motor thermal overload is openening, as well as the reason for the lack of cool air. Am I on the right track? What does a recharge cost?

You should have two copper tubes going to the condensing unit. One should be larger than the other. The larger of the two should be cold & sweating. The smaller copper tube should be warmer than the outside temperature by about 10 degrees. Compressor motors are cooled by the flow of refrigerant past the motor coils. Refrigerant is drawn through the motor and into the suction side of the compressor. When you are low on refrigerant the cooling of the motor is compromised. That is the reason for having a low pressure cutout switch installed on the condensing unit. You could very well be tripping that switch if the refrigerant level is low. That also could be the reason you aren't getting much cool in the house. You mentioned the compressor current draw of 5 to 6 amps. That doesn't sound excessive to me at all, but sounds like a compressor under a much lighter load than maximum. I'll bet you are hitting the low pressure cutout after the A/C unit has run for a while. The only way to tell for sure is to put a gauge set on and measure the high & low side pressures. If you can't do that you'll have to call someone in. Assuming that the diagnosis IS low refrigerant levels don't let the tech get away by just adding charge to your unit. You almost certainly have a leak, that's why the charge is low. Fix the leak first THEN recharge. There's no way to tell how much such an operation should cost because there's no way to tell just what might be leaking. A leaking coil will cost more, a loose line coupling will be cheap, assuming the contractor is honest.

I'm kinda thinking like Jug. Are you 100% sure it's the internal o/l ? Or a pressure switch.

Yeah, I'm absolutely sure it's the motor internal overloads that are opening. I put a Fluke across them to verify. The motor is a single phase with two windings (start and run) with a third leg that has the thermal overload. The motor, drawn out, looks like a simple Y-connected motor, with the third phase having the switch instead of a winding. I know the Cap is good because the fan motor runs of the same Cap as the compressor. To tell you the truth, I thought that it might be a low pressure switch at first, but I found the schematic tucked inside the unit where the contactor and Cap are and found that there is no low pressure switch! Strange. Anyway, I have a tech coming Saturday to hook up meters and gauges and stuff (I'm an electrician, not a mechanic : ) and I'll see from there. I'll post what I find. Thanks for the help!! :)

It could be an "el cheapo" condensing unit and the designers figured that the motor high temp cutout would substitute for the low pressure switch. The current measurements you posted implies that your motor isn't overloaded. My bet is that the tech will find a low side pressure (assuming R22) of between 0 and 25 psi. The cause of the out of spec low side pressure could be a simple loss of refrigerant OR you could have a restriction in the line set somewhere, perhaps a plugged filter/drier in the liquid line. Post back and let us know if our prognostications are accurate.

The motor is a single phase with two windings (start and run) with a third leg that has the thermal overload. The motor, drawn out, looks like a simple Y-connected motor, with the third phase having the switch instead of a winding.

The big copper line has to be cold and wet.The small line warm. if not can be low freon like said.

As you are a electrician you can try and be there when the compressor starts and pull the start wire off after its running. If it keeps on running then get a full start kit for it with a potential relay. Years back there was a whole line of compressors. That after a time they would take out the fuses. After we put a start kit on that had a potential in it all of them just ran and ran . They had a small short it the start to run field.
my .02 cent have had to put up with Frances and jeanne here . Think I got it right

ED :eek: :eek:

I have a guy coming (a friend of a friend) who will do a high / low pressure test. I checked the coils as someone suggested and they are not frozen up, so if there was a leak, it's all gone by now :cool: . The large pipe is not getting cool as it should, but the small pipe does get warm, but not as warm as I would expect (80 - 90 deg?).
If the tech suggests a new compressor due to a winding problem, I'll try the idea out about disconnecting the start winding (after starting) and look into the kit you suggested.
Thanks to all the tips, I definately learned alot more about AC's than I probably should know by reading these and the many posts from other peoples problems too. I'll post tomorrow what my tech finds out. I'm guessing a leak somewhere. I hope that's the case anyway, It would be cheaper than a new condensor unit.
By the way, it's a Janitrol, and yes, I think it's cheap. The private community I live in consists of 160 homes all built within a year. I'm sure savings were "made" somewhere.
Thanks again.