Trane Central Air Unit

[Mrwag]

I have a Trane heat pump.  It has been cycling on and off continuously for a couple of weeks.  I had an a/c man out to look at it and he said the condensor coils needed to be cleaned.  Wanted $500.00 to take the coils out and clean them.  I got some of the professional coil cleaner from an a/c acquaintance and cleaned them myself without taking them out.  The air quit cycling on and off but now the outside unit keeps running even when the inside unit kicks off.  If I turn it off at the thermostat and then turn it back on the inside unit kicks on with the outside unit.  It seems to be cooling o.k. but this morning the floor around the air handler and the door to the air handler seemed unusually cold. It was working normally for a couple of on and off cycles this morning but this afternoon the outside unit won't shut off on it's own some of the time.  The unit is about 8 years old and I admit I have not had it serviced as often as I should have.  Does this sound like something I can take care of on my own.  I am a novice when it comes to air conditioning but am mechanically inclined in other ways and able to follow directions.  Hope someone can help me with this. 

[hvacdrd]

Can you tell if it is just the fan running or the compressor as well? If the outside unit is running without the inside fan running it would surely ice up the coil inside in a hurry.

Turn off power to the unit outside and set the tstat to off. Remove the access panel on the heat pump and look for the contactor (image attatched) - see if the contacts are stuck closed. With all power off and no call for cooling they should not be closed. If they are it will be time for a new contactor.

contactor.bmp

[Rrey199]

 I don't think the AC guy was going to take the coils out either. His plan was to do what you did, but for $500.

The contactor getting stuck closed from the contacts welding is a possibility, but that's usually a one time thing, rather than a recurring problem.

Make sure the wire to the reversing valve (O from the stat and usually orange) isn't tied to the wire to the condenser contactor (Y from the tstst and usually yellow) This is a common shortcut by the guys who don't really know heat pumps, and a quick fix if you have a bad wire. If they are tied together, the condenser will come on when the stat is set to 'cool' event when there is no call for A/C. The condenser will shut off when you set the stat to 'off' or 'heat'

Give that a try.

Rusty

[Mrwag]

Thanks for the response.  There was black burn marks on the contactor.   It has been cooler so I left the air off for a few days and then I replaced the contactor with a new one.  Now the outside unit runs all the time.  The inside one kicks off and on as it should but the outside never kicks off.  I bought a new thermostat today and am going to replace it tonight.  Someone told me that the outside unit runs a few minutes before the inside one kicks on and a few minutes after it kicks off, is this true?   

[hvacdrd]

Hold off on the thermostat for a minute, let's narrow down the problem first. Is the contactor pulled in while the unit is on outside with the tstat set to 'off"?

[Mrwag]

Checked the contacts and they are not stuck closed.  They move very freely. 

[hvacdrd]

OK - now if you turn on power to the A/C does it come on with the contacts not pulled in?

[Mrwag]

When the A/C is set to off and the fun is running outside the contacts are not pulled in.  When I turn the A/C on the contacts pull in.  The condensor my be on inside.  I don't hear it but the air handler door feels cool to touch.

[hvacdrd]

So if I am understanding this correctly the condenser (unit outside) fan runs continuous when power is on even if the contactor is not pulled in?  Can you hear the compressor running as well? Does it seem like the fan is running at full speed? Follow the three wires coming from the condenser fan motor and tell me where they connect to relative to the contactor. Two of the leads may go to the capacitor.

[Mrwag]

The orange wire connects at the bottom end connection of the contactor then goes to the capicator.  The heavy duty red wire goes from the compressor to the contactor and then hooks to the capicator.  The same end black wire goes from the compressor to the relay and the opposite end of this relay switch is the house current.     

[hvacdrd]

Since I was a bit confused by that I figured a picture is in order. Here is how it should be wired (or some variation of this) as long as the wires all connect in some way to match this configuration. There may be more wires to the capacitor than shown if it is a dual capacitor (serves the compressor and condenser fan motor). For now lets disregard any wires going to the ccompressor and focus on the 3 wires going to the condenser fan motor.

contactor.bmp

[Mrwag]

I think we have it figured out.  It seems that we had the wrong contactor.  We bought a new one that had two contacts and the one on our unit had only one contact.  We replaced the contactor last night and everything seems to be working fine.