Trane X Heatpump only works in emergency.

Greetings all,

Hope everyone had a nice Christmas.


Tried searching everywhere, including here, and have not found my exact problem happening.

A little background first;

Hunter programmable thermostat
Trane Xsomething compressor
Trane XL air handler

Summer before last, compressor capacitor was replaced by HVAC service company.
Last summer, 5 amp fuse for Thermostat blew.

NORMAL SEQUENCE OF OPERATION:
Set temp, Thermo goes click, stage 1 and 2 lights start blinking, fan and compressor come on, comfort ensues. Stage 2 light on thermo may or may not go off, depending on what the system is doing.

Now for my problem.

Set Thermostat for heat or auto heat, and temp to a level that turns it on. Hear Thermostat go click, see light for stage 1 start blinking, but not stage 2 ,hear click, all lights, including display backlight shut off and stage one light just blinks. No fan, No compressor noise. Put it in Emergency Heat mode, Stage 1 light lights up red as it should, fan comes on, expensive heat blows, Wife doesn't freeze.

The Thermo manual says the blinking means it is in a "Hold Mode" that the thermo has to prevent rapid cycling of the compressor. The troubleshooting section of the manual just says to replace the thermo if heat does not come on. I thought the batteries might be dead, even though they are only for backup, so I replaced them. When I removed the thermo from the wall, I blew the fuse on the air handler that feeds the thermo. All circuit breakers for all units are good and reset, no change.

Since the fan works in Emergency mode, and the fuse blew, I am leaning towards it being a Thermostat problem, not a unit one. Luckily, I am installing a programmable thermostat in my Mom-in-laws home today, and will be able to use her old one to test my unit.

I just thought I would run this by everyone here and see what anyone thought, or they have had this exact problem.


Thanks in advance,

Chris

You removed thermo wothout disconnecting any wires? Could be there is exposed wire in cable, movement of thermo caused it to contact another "hot" wire blowing fuze. Could be control wires in contact that don't blow fuse but "confuse" thermo. Check connections to thermo for tightness and over stripped insulation allowing cross connections.

Not familiar with your system, we recently installed heat pump, only electrical strip, "expensive" heat would come on. Even the pro couldn't figure it out. Contacted factory rep, he too was unfamiliar with new thermo. We put him on speaker phone while he rummaged thru all sorts of manuals etc. Turned into conference call with engineer. With me inside, tech outside, everybody on conference call we swapped wires, and all sorts of stuff. Wife inside reading small owners brochure complaing of heat coming on going off AC sporadically shooting cold air, then she sez, " Did anyone tell thermostat there was a heat pump?" Huh? Yup, had to go 12 steps into "set up" on thermo an click "Yes" when display said " Heat pump?"

I 'spect a HVAC pro should come along here soon with a real answer. Let us know if replacing thermo works.

No, thermo didn't work. Old one was heat pump specific, new one is switched to heat pump and electric. Bought a new one after all, same problem. I hope it's not a control board, those things are expensive!

Well, ended up replacing blown transformer, no change. When it is powered up, but off, the green CFM LED flickers more than blinks, then goes off, the starts the flickering again. It does this rythmically, so I know it is trying to tell me something, but the flicker is impossible to decipher. The green FAN LED stays off, and two other unlabeled green LED's on the side are dimly lit constantly. What does this mean? I cannot find any info on diagnostic codes or status indicators for this air handler. TRANE 4TEE3f31A1000A. Why is that?

Well since your not getting any answers here..I hate to do it, but try here.

http://hvac-talk.com/vbb/forum.php?

Thank you so very much!

inspectorD said:

Well since your not getting any answers here..I hate to do it, but try here.

http://hvac-talk.com/vbb/forum.php?

Click to expand...

90+ views, 0 replies over there. They don't like DIY'ers over there, so I tried not to sound like one in my post. Maybe I failed?

Hey, it sounds like your heat pump is being locked out for some reason. Have you tried running the system in cooling to verify the outdoor unit is operational at all? If the cooling works you can factor that possibility out. If its locked out it may be because it is below the LTCO (low temperature cut out) or the the balance point. When its in hold mode its gathering information from the system components to see which steps to take to provide what you are asking from it. It does this based on how the system is set up through the thermostat options and the various dip switches and setpoints at the heat pump. System setpoints and tstat setup may want to be gone through again, the tstat may not be communicating with the heat pump. Hope you get it figured out!

Sorry, should have come on here to tell of my resolution sooner, but between work and home, I just forgot. It was, after all, the control board. Or, more correctly, a combination of control board and transformer. I had the transformer fuse blow last summer, and again when I was troubleshooting. I believe that was indicative of the transformer's impending failure. Turns out the secondary coil burnt out, so no 24VAC. After popping in a transformer of the same rating and voltages I just happened to have on my shelf in the garage, she fired right up. Thank you Bunn Coffee maker company for specing a transformer identical to trane's, albeit slightly larger.

Thank you, those who tried to help!

Chris

Another thing. I called several parts houses, here in Fredericksburg, up in the DC area, and even down in Richmond. Prices varied between $126 to $159 for the teeny,tiny board, and no one stocked it. A quick Internet search led me to a place in Pennsylvania, where I got it for $45 postpaid to my door! I had it 2 days after it shipped.