View Full Version : House AC Problem Update

Russ Filtz
03-16-2010, 4:30 PM
Got a tech to check things out. Capacitor and transfer switch are good supposedly, but the thing is drawing 138 amps when trying to start which pops the breaker naturally. He said it's the compressor unit, which is integral w/ the compressor motor. True of most units or is the motor separate typically?

I don't want to replace a compressor at $1200-1500 if possible (short selling the house soon). It's a Goodman 5-ton unit. As we were walking out to the unit, it seemed to be trying to start itself (you could hear a short hum) even though the thermostat was in the OFF position! :eek:

Dave Johnson29
03-16-2010, 6:31 PM

It is possible the compressor is full of condensed freon or oil or a mix of both. Maybe not full but enough at the top of the stroke to prevent the piston going through the compression stroke.

An AC service man should be able to drain, vacuum and refill for a lot less than 1200-bucks.

Russ Filtz
03-16-2010, 7:45 PM
How do you tell if this is the case vs just a bad motor or short? Is this even more likely when switching from heat pump mode to cooling?

OK it's even weirder. When I flip to heating mode, the breaker never pops, then outside compressor fan runs, then every minute or so it sounds like the compressor tries to kick on with a whine, then I see a spark near the ground wire and cover plate that's over the capacitor, then the cycle starts over. Fan keeps running throughout. Breaker doesn't pop like it does on cooling mode though. Was getting some heat out, but not sure if it's coming from the emergency electrical element inside or the heat pump itself.

Dave Johnson29
03-16-2010, 8:41 PM

Heating and cooling is the same to the motor and compressor. It just reverses the direction of flow. That's a simple explanation but basically the condenser becomes the evaporator and the evaporator the condenser.

The click and stall is still the compressor. It may be a bad motor or compressor, but I'd get a guy to drain, vacuum and test cycle. If it turns OK, then refill.

It's hard to imagine the motor is faulty and even less likely the compressor, whether it is vane type or piston.

If the motor has a start capacitor or a run capacitor or both it may be that one or both are shorted or open.

Too many "ifs"

Not something that can really be diagnosed via a keyboard. Replacing motor and/or compressor would be about 2 weeks down my list.

Tom Godley
03-17-2010, 12:12 AM
You should not be getting any sparks on start up. This sounds like the start or run capacitor being bad.

The hum is the motor inside the compressor body trying to start -- the thermal overload opens in an attempt to save the windings. The motor and compressor are sealed -- they are one unit. What you are describing is a very common failure of the compressor.

Removing the refrigerant will not change anything -- ?? And if it was just low the start cycle would not trip the beaker

The hum you may be hearing is more than likely the compressor heater -- it is on when the compressor is idle

Sometimes the compressors can get stuck and the motor is not powerful enough to overcome the force - this often happens when you try to start an older unit for the first time. You can add what is called a hard start kit to the unit -- this adds an extra jolt to get the compressor going - they can often extend the life of the unit. I have even heard of hiting the compressor with a rubber mallet .

Al Willits
03-17-2010, 8:25 AM
If your in Florida, I doubt it's freon locked, in fact I'd bet on it, also for it to be oil locked someone would have had to added a lot of oil to the system.

You got sparks, you have more problems than a hard start kit can cure.
A tech should be able to ohm out the compressor to see if the motor iside is shorted or check to see if the pump is locked up.

Get a second opinion if you don't trust the first guy, don't tell him what the first tech said, and see what they say.