Lennox Thermostat Probem

Old 10-15-12, 01:53 PM
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Lennox Thermostat Probem

I have a Lennox heatpump with auxiliary heat which was installed exactly five years ago. It has worked until last week. The problem is the thermostat seems to "forget" where it is in the program, and goes what appears to be a to a circulate state with a small amount of heat and a slow fan speed. The problem is intermittant. Here are the things I have confirmed:
1. The batteries in the thermostat are new, there are 24 volts to the thermostat.
2. When the thermostat is working correctly, there is a faint click when the thermostat changes modes, it does not have to be mounted on the wall to make the sound.
3. When it is not working, it will change modes on the face, but there is not a click sound.
4. When it is not working the furnace can not be turned off from the thermostat.
5. I checked the EHC1 control board. The two green led's are indicating no problem with the board.
6. The thermostat indicator light W1 (an amber led) on the EHC1 board is on continously. I called Lennox and they told me this indicated that the auxiliary heat is on.
7. The filters are new.
8. The model numbers are: Heatpump - XP13Elite; BlowerCoil CBX32MV; Thermostat - Elite Series X4147; Electric Heat - Evenheater ECB29EH
9. 5 year warranty expired August 25, 2012.

I called Lennox for additional troubleshooting help, they don't provide any. I am competent with a multi-meter and can read a schematic. Before tracing this through I though that someone that has some experience with Lennox could tell me to do something like replace the thermostat (about $300 from the local guy....ouch) or replace the EHC1 Control Board on which he couldn't find a price....a bad sign...I live in a small town.

I would appreciate some trouble shooting help or being pointed toward where to find something beyond the installation instructions that came with the furnace and thermostat.

Thank you.
Old 10-16-12, 01:36 PM
user 10's Avatar
Join Date: Mar 2004
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The lennox thermostat appears to be a re-batched honeywell.

To determine what a suitable replacement is, remove the stat from the base and post which terminals are connected to wires.

Verify that the stat is bad...

1. Jumper terminals R and G - the fan should come on
2. Jumper terminals R, G, and Y - the heatpump should come on in heating mode. The supply air should be luke warm after a few minutes (When O is energized too it should run in cooling mode)
3. Jumper terminals R, G, Y, and Aux/W1 - the air should be very warm after a few minutes
4. Jumper R and W1/aux (or E if it's connected) - the air should be slightly cooler than it was with the heatpump and aux heat running at the same time

Don't let any jumper come into contact with terminal C.

If that the system doesn't respond as it should, call a technician.

Otherwise, replace the t-stat.
Old 10-16-12, 06:15 PM
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I am almost certain it is your thermostat. There is a watch battery behind the display. It is hard to get to. I would try that first. If you don't want to try that or it doesn't work then I would replace your thermostat with a Honeywell TH8320 VisionPro thermostat. Because you don't hear the click, it is as though the relay in the thermostat is either faulty or there is not enough power for the relay to operate.

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