How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Richard Your Own Question
Richard, Technical Manager
Category: HVAC
Satisfied Customers: 1514
Experience:  27 years of Experience, NATE Certified, professional trainer
Type Your HVAC Question Here...
Richard is online now
A new question is answered every 9 seconds

Lennox heatpump won't shut off. What should I do?

Customer Question

My heat pump won't shut off (heating). It is a Lennox m/n CB29M-41-1P unit controlled by a Lux PT 2110 thermostat. I've replaced the batteries on the thermostat and have changed settings (heat/cool/off). Nothing seems to work except for hitting the breakers on the heat pump. OAT is 62F. Thermostat reads 72F. Thermostat is set to 68F. Any ideas?
Submitted: 5 years ago.
Category: HVAC
Expert:  Richard replied 5 years ago.

Hello it sounds like the contactor welded itself shut. So to check this go to the out door unit turn off power and remove the control cover look for the contactor it will have a plunger in the middle. Push down and release it should move freely. If it is stuck you can break it free but you will need a new one. They run about 20 to 30 dollars. Once you check this let me know if that is or is not the issue and we can continue. Thank you Richard

Lennox Heatpump Contactor

Customer: replied 5 years ago.
Thanks for the reply. Obviously, this is going to take me a moment to get out to the unit, drop power to it and follow your other instructions. I'll check back with you once I've done this.
Expert:  Richard replied 5 years ago.
OK Im here for a while
Customer: replied 5 years ago.
No joy I'm afraid. I located the contactor you mentioned without issue. The plunger in the middle moves freely. After making sure it moves up/down or in/out freely, I turned reset the breakers on the heat pump and it instantly kicked on. BTW, I verified that the thermostat is set to "Off". Any more ideas?
Expert:  Richard replied 5 years ago.
Hello Ok no go to the thermostat ( turn power off first) remove the wire on the Y terminal and tape it off. Will the unit still run? If so go to the furnace and do the same thing. Lets narrow it down to the indoor section or thermostat. Let me know we are alsomost there. Richard
Customer: replied 5 years ago.
On it. I'll check back once I've taken these steps.
Expert:  Richard replied 5 years ago.
Customer: replied 5 years ago.

OK. I dropped power. Disconnected wire connected to Y terminal on the thermostat. Restored power. Unit still kicked on despite thermostat in "Off" position. Dropped power again. I'm in the process of trying to find the right Y terminal on the indoor unit to pull a wire from. Sorry it's taking me so long. This isn't exactly my field of expertise!

Expert:  Richard replied 5 years ago.
Hello take you time, you have a short somehwere if pulling the Y off the thermostat did not do it and the contactor is not welded shut. You can also go to the outdoor unit tere should be two thermostat wires going out there just disconnect one of them as well it should shut off. On the furnace there will be two wires on the Y terminal pull them both off then measure for voltage between Y and C if there is power 24 volts and you know the thermostat is off you have a faled relay on the board.
Customer: replied 5 years ago.
OK. I disconnected the Y terminal wiring from the Lennox Elite heat pump unit. The heat pump now responds to settings on the thermostate. Also, the outdoor compressor is running constantly. What does this tell you at this point? (BTW, I do not have a volt meter to check the power going between Y and C contact points.)
Expert:  Richard replied 5 years ago.

Hello Ok we are missing something in translation. You disconnect the Y which is the compressor wire from the termostat. Yet you say it responds to the thermostat but compressor is running all the time? It's one or the other either the unit turn on and off with the thermostat or it runs all the time.

Next when you say compressor do you mean the out door unit? condensor? or the compressor motor inside the condensing unit? Richard

Customer: replied 5 years ago.

Sorry I wasn't clearer.

I disconnected the wire from the Y terminal on the thermostat on the wall. There was no change in behavior. The heat pump and condenser both kicked on, regardless of thermostat settings.

I disconnected the wiring from the Y terminal on the circuit board within the heat pump inside. With this action, the heat pump now responds to thermostat settings. Also, the outside unit (condenser, not compressor -- sorry) runs regardless of thermostat settings.

Please let me know if you need more clarification or information.

Expert:  Richard replied 5 years ago.
Hello Ok that make more sense in the future lets call the outdoo runit the condensor and the indoor unit the air handler the system is a heat Makes it easier. So, with the Y wire off the air handerl we have a condensor that is running yet the contactor moves freely? correct. Next is we have a short most likely in the thermostat wire going from the AH to the condensor. With out a meter we are doing some guessing here. However tis is a simple repair you can try. First look at the wire and make sure nothing chewed it or thhere ar enot breaks or cuts in in. Next we will have to replace the wire can you do this? If you can get a volt meter this will make it much easier. Richhard
Richard and other HVAC Specialists are ready to help you
Customer: replied 5 years ago.

Got it. Forgive my ignorance and use of the wrong terminology.

You are correct. With the Y wire off the air handler the condensor is running yet the contactor moves freely.

I checked out the wiring running to the condensor outside. The wiring (including the wire that runs to a Y1 terminal) is wrapped in a sheathing that has a point where there was some wear to it (it had been rubbing against an edge of sheet metal on the unit). However, that part of the wiring bundle/sheathing had some electric tape wrapped around it.

Last December, I had to have a service call because the system wouldn't run at all. The technician found that the sheathing containing the wiring bundle had been rubbing against the sheet metal edge; exposing some of the wiring. He wrapped it in eletric tape and that seemed to fix things. Hmm... even though this wiring bundle was wrapped in electric tape, I'm wondering if this is the root cause? Thoughts?

Expert:  Richard replied 5 years ago.
More than likey, the electrical tape was nothing more than a band aid. I would replace the iore or cut it back if there is enough Richard
Customer: replied 5 years ago.

Richard, I think we've got it. I stripped back enough of the sheathing on the wiring bundle to expose the wiring where the insulation around the individual wires had been worn away. I wrapped each of the wires that had insulation worn away in electrical tape (including the yellow wire). I reconnected all disconnected wiring and restored power to the air handler and the condensor. The system now responds to settings from the thermostat (heat/cool, on/off). While using the electrical tape in place of properly insulated wiring isn't a long term fix, I at least know where to root of the problem is. Thank you very much.

Expert:  Richard replied 5 years ago.
Your welcome have a great day