DIY Home Improvement Forum banner
1 - 20 of 22 Posts

·
Registered
Joined
·
8 Posts
Discussion Starter · #1 ·
My Lennox HP29-030-1P AC keeps shutting off the cooling and repairman is lost for answers. They've been out 5x's, pressures are normal. Some days the system will cool for 12 hours and other days under 2 hours. I;ll turn off system and let compressor cool and then it will turn back on. Techincan has never seen this problem. They called Lennox but they said they didnt know. Curious, can you replace the thermocoupler on the compressor (just a guess that's the problem)? What else could be wrong?
 

·
Hvac Pro
Joined
·
23,688 Posts
There is no thermocoupler. Does the compressor get so hot that you cannot touch it? Has an internal overload inside but that usually takes 6 or more hours to reset. Did they check the capacitor to see if it is weak?
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #3 ·
Yes the compressor get very hot. Technicain ran water from outside hose on it to cool off so he could work on it. Yes, the capacitor was weak and was replaced, plus they added a "start cap"...all meter reading and pressures seems right on. Note: the technician has not worked on system when is was not working since I had reset the system by the time they had arrived. I will not reset next time. One tech has 32 year experience and is clueless at this poiont. I keep worrying its the compressor that's going bad. Once it quits cooling the interior thermostat has to be turned to "off" position and I typicaly wait 30 minutes to turn back on (some days it may take 3+ hours fo the the sysytem to start cooling).
 

·
I'm Your Huckleberry
Joined
·
5,884 Posts
There is no thermocoupler. Does the compressor get so hot that you cannot touch it? Has an internal overload inside but that usually takes 6 or more hours to reset. Did they check the capacitor to see if it is weak?
If you run continuous water over the compressor from a garden hose, 15 minutes max.
 

·
Hvac Pro
Joined
·
23,688 Posts
If it is overheating the condensor fan may be stopping in mid cycle but that usually blows the internal relief valve which sounds like a rifle being fired. If the fan is slowing down it may overheat the compressor. I don't do heat pumps but have heard that a faulty reversing valve can cause it to over heat??? Marty are you out there. We have some heatpump techs here.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #6 ·
Fan appears to be working fine. Any chance it could be my thermostat? I've been tracking the problem for the past week...based on ambient temps the system seems to quit cooling on days greater than 80 degrees but have found nights in the 70's affects the system similarily. The system always works (fan, blower) just the ac quits cooling. Last thought, the time it takes for thr sysytem to begin cooling again takes anywhere from 30 minutes to 4 hours. I have found the longer the I keep the thermostat in the "off" cooling positon (once the cooling stops) the longer the ac works once it turns back on.
 

·
Hvac Pro
Joined
·
23,688 Posts
Thermostat is not the problem. Sounds like it is a cumulative effect/heat buildup in the windings of the compressor. Hang in here and maybe one of our heatpump guys will know about the reversing valve possibility.
 

·
Registered
Joined
·
1,407 Posts
You can test a reverse valve using a small magnet.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #9 ·
Thanks. I'll have them test tomorrow. AC been cooling great past 6 hours blowing out 55 degree air. Unfortunalely in a few minutes or hours out it will stop cooling. Thanks for all your help!
 

·
Registered
Joined
·
8 Posts
Did they check your pressures? Sounds like it could be a plugged condenser coil. It might not looked plugged, but dirt and cottonwood can get caught in between the fins causing the compressor to overheat and trip out on high head pressure.
 

·
Registered
Joined
·
2,362 Posts
If everything works right when he's there then I'd suggest concentrating on the txv . Ask what the superheat is when they come out next time.
 

·
HVAC
Joined
·
40 Posts
By resetting the outdoor unit you can be clearing any fault codes that can assist the technician. If your unit has a high pressure switch that should be keeping the compressor from shutting off that way. If it has a high pressure switch but is still shutting off by thermal cut off it would most likely be due to not enough superheat keeping compressor cool. If problem persist and you dont have a high presssure switch maybe one could be installed on the defrost board and this would help in diagnostics.


KAVF
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #13 ·
Manufacturer rep came out today to tell me compressor is dying. It appears my capacitor instead of failing continued to provide low power to the compressor for at least past 6 months most likely wearing out compressor. Having high 90 degree weather and compressor hots overlead and stops cooling aobut every hour for 5-10 minutes.

Question, this system is 10 years old...new system is $6000-6500 and new compressor $1600. Cash poor right now and thinking of just replacing compressor hoping AC will work for at least the next few years. Am I wrong to replace just compressor?
 

·
Hvac Pro
Joined
·
23,688 Posts
I would get the compressor replaced and that is a reasonable price. Some Lennox units had 10 year warranty on compressors and some had 5. Did they check. If you have the owners manual and papers it should be at the back of them. Post the serial # and I can give you the date of manufacture. They will give you 6 months past it if you have no bill of sale.
 

·
Registered
Joined
·
1,407 Posts
If the general condition of the AC is good ( evap coil, Condenser coil, funrnace ) you have more than 10 years.
 

·
Hvac Pro
Joined
·
23,688 Posts
reread my post I added to it. compressor may have a warranty.
 

·
Hvac Pro
Joined
·
23,688 Posts
I found the owners manual on Davenet and it has a 10 yr limited warranty on the compressor and 5 on parts. Unless it was marketed or sold differently in your area. Cannot post the link as it is blocked for out of production units. Post the serial #. Talk to the district manager if necessary.
 
1 - 20 of 22 Posts
Top