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Lennox HP26-461-3P

I have a Lennox HP that has worked well until this heating season. When I call for heat, The aux heat comes on at the same time as the compressor even though outside temp is 55 degrees and the demand for heat in the house is only 1 degree above the existing temp in the room. The defrost board shows normal, i.e., the LEDs are blinking together. I suspect a bad defrost board and I cannot find a replacement. It is the DTL-100000-LXA (68J8401).

Also, today, the blower started to run at a slow speed resulting in the compressor tripping on high head pressure. Changed the capacitor with no change in performance.

Any ideas on either issue?


  • IronmanIronman Member Posts: 5,681
    Do you have a digital multi meter and do you know how to use it?

    There could be several causes for your problems, but trying to diagnose by guessing and parts changing is not the way to go.

    How old is the equipment?
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • GWGW Member Posts: 3,766
    Look at your stat, the stat normally controls the functions.

    If a new cap didn’t work then replace the motor. Or thy a different speed on the motor. I’m assuming the new cap was indeed good
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • unclejohnunclejohn Member Posts: 1,572
    May have a stuck defrost relay contact for the 1st stage of electric heat. As for the fan I don't know.
  • G19348G19348 Member Posts: 5
    Thanks for the feedback and your patience. I am still learning how to use the site.

    Here is some more info.

    1. I have a Fluke multimeter and i know how to use it.

    2. The Heat Pump is 25 years old. I had a new defrost board installed in 1997 under warranty.

    3. I had a small freon leak that was fixed in 2015.

    4. I replaced the blower in 2014 because the bearings went bad.

    5 . In 2017 i installed a Honeywell WIFI thermostat. Three weeks ago when i started this heating season the heaters kept coming coming on. Then i reinstalled my Chronotherm III. Still have the problem with heaters coming on. By the way, the AC works perfect.

    6. While troubleshooting the blower, I lifted the black wire (high speed) from the motor relay and put the yellow wire (medium speed) in its place. The blower is working on medium speed to give me heat in the house. The filter is new so air flow is good and keeping the compressor from tripping on high head pressure.

    7. When the black wire was connected to the motor relay the motor was getting very hot (250+ F) and tripped on thermals. When i disconnected the wire the motor temp dropped from about 250 F to 150 F.

    8. I used the Fluke to check the capacitor and the new and old caps checked out satisfactory.

    9. The motor is getting 240 volt, 122 V from orange common and 122V from either black or yellow lead which is expected.

    10. Could the motor be stuck on the start circuit and putting more amps then needed in the motor?

    11. Not sure which relay can be stuck. Is there a way to check with my Fluke? Should i lift the W1 wire in the condensing unit outside and see if i am still getting 24V at the lug?

    I appreciate all the help!

  • unclejohnunclejohn Member Posts: 1,572
    Most likley the high speed winding is shot. If you remove the W1 from the out door unit and the heat goes off it's the defrost relay or board.
  • IronmanIronman Member Posts: 5,681
    Does the back up heat go off if you disconnect the white wire from the heat pump?
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • G19348G19348 Member Posts: 5
    I am doing that troubleshooting on Monday. Right now we are predicting 21 F tonight and 29F tomorrow night. Gosh forbid i screw something up and loose heat. I am thinking like you are thinking (i think). If the aux heat goes off then it is a defrost card issue. If not it is in the cabinet. Is that what you are thinking?
  • G19348G19348 Member Posts: 5
    I am also pulling the fan next week. Getting a new motor was very hard because i am not lennox authorized. I was going to take the motor to a lical mtor shop to see if they would test and fix/rewind. Any leads on getting a motor?
  • IronmanIronman Member Posts: 5,681
    25 years is 10 years longer than average life expectancy. You really should consider new equipment.

    As far as a motor goes, IDK of anyone that rebuilds fractional horsepower motors anymore. It's cheaper to buy a new one.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • G19348G19348 Member Posts: 5
    The unit is still operating with the blower medium lug connected.
    Blower motors range from $293 to $565. Then I have the relay board to track down. I am thinking that it is time to upgrade. I hate to give up the unit because it worked so well for many years. However, efficiency wise it makes sense to get a high SEER unit.

    This web site has offered more help then any other. Most other websites do not appreciate the inquisitive DIY. Often they cite personal safety however, most people that get into this type of T-Shoot are knowledgeable people.
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