Hi folks I need some input from the forum. This is my first posting though I have lurked here a while.
Late last week I noticed that my downstairs AC (technical details provided a the end of this post) was putting out air at the ambient inside air temapture. I went outside and instantly noticed that while the blower motor in the condesor was running the compressor was not (it is a reciprocating compressor that makes an obvious though not loud noise when running). A also felt the suction line and it was the ambient outside tempature. So the inside and outside blower motors were on but the compresser was not. I sat there and "watched" it for a while and all of a sudden the compressor starts to groan and starts up but sounds like it is struggling for about 10-15 seconds. Further experimentation shows that the compressor will always start if the time between the last time it was run and the next time it is started is 10 or more minutes. Any less time than that and the compressor will start around 65-75% of the time (often making some odd protest noises). When the compressor doesn't start the outside and inside blower motors run and the compressor does eventually start with some protest about 5-10 mins. later. Once on the compressor stays on until the thermostat shuts everything off. My Chronotherm III thermostat has a 5-6 minute delay built in but that does not appear to be sufficient.
So I call the contractor I have used before to replace the upstairs HVAC equipement (and been happy with) and the earliest they could come out was today (Tuesday). Which is fine since I know they are busy. I turn off the downstairs AC since leaving a sometimes stalled compressor presumably powered seems like a bad idea to me.
So the tech comes out today and unfortunately I am out of town so my wife speaks with him. He says the compressor has a cracked valve and will "eventually" need to replaced (this was indicated by the refrigerent pressures being off as the low side was high and the high side was low) but that the intermittent compressor operation is due to our Thermostat and that is what needs to be replaced. He told my wife that it was okay to operate the unit and that there was no need to replace the compressor until it died completely. It does cool the house fine, though I did notice that as a heat pump it was less effective this winter than before (it seemed to run much more often and for great lengths of time between cycles).
So my questions are:
One I don't believe that the theormostat controls the compressor directly so I do not see how that can be the main problem. It is a high quality Chronotherm Honeywell installed about two years ago. If the thermostat was the problem, wouldn't it impact the inside and outside blower motors as well?
Two worrying about my theormstat when I have a "sick" compressor seems to me like a mechanic trying to sell me new tires for a car that has a dying engine :-).
Three I don't believe it is safe for my wife to run the AC with a compressor that is may burn itself out if it doesn't start.
Four the tech did mention that there is generally a 10 year warranty on compressor from Trane and this unit is currently 8 years old. How do I go about checking on this as the unit was installed prior to my purchase of the home and I don't have the paperwork.
A bit about my equipment, the condesor unit is Trane SEER 10 heat pump (I think XL1000 but I am out of town so cannot check). It was manufactured in the 1st half of 1997 and appears to have been installed on 7/17/1997 due to this date being scrawled on the back of it. The inside unit is a Trane gas furance circa 1986, original to the house. I assume the evaporator is original to that time but I am not sure. Based on the upstairs unit, the orginal heat pump was pobably an old GE from 1986. The thermostat is a contractor grade Chornotherm III (NOT the cheapened Home Depot version) that was installed about two years ago.
Sorry for the length of my post and I appreciate your advice.