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Blower not coming on

Ruffinitagain
Ruffinitagain Member Posts: 3
in Gas Heating

Hi,

The blower in my Lennox EL180UHE upflow furnace isn't coming on, although it fires up just fine. Yep, out of warranty by a year.…I tried replacing the thermostat, and that didn't help, but saw a reverse voltage polarity code, so I checked with the multimeter and the voltage difference was fine. Then I replaced the 42J3201 transformer on a hunch with no joy….

Any suggestions? I'm not getting a read between the circ terminal and the fan terminal, so I'm concerned that the board may be compromised…

ENR in central NJ

mattmia2

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,388

    Can you post a pic of the wiring diagram?

    That furnace has an ECM motor which is more difficult to troubleshoot. There are you tube videos on how to do that or call a professional.

    Replacing parts will do no good until you find the problem. Two terminals on the motor should have constant power the rest of the wires are for control of the motor speed.

    Those motors are $$$$$

    mattmia2
  • HomerJSmith
    HomerJSmith Member Posts: 2,635
    edited December 3

    Sometimes there is a thermo-disc sensor on the blower housing. It may have tripped. There is a lag time from when a heater fires up and the blower starts, this prevents cold air in the ducts from blowing into the building until the temp in the heat exchange rises. That furnace probably has a trouble shooting section in the manual that may help you.

    With the thermostat calling for heat, take the blower door off the furnace and reach in and spin the blower cage and see if it turns easily. If it does, hold the door switch closed for several min and see what happens.

    Unplug the blower wiring connection to the board and re-plug it back in. Unplug the power first from the wall, tho.

  • 109A_5
    109A_5 Member Posts: 1,587

    Hello Ruffinitagain,

    So far I can't find a wiring diagram. There may or may not be a temperature sensor on the heat exchanger for the blower start, seems like the blower is timed-on delay is controlled by the board. Maybe you can verify that the board can actually engage the blower by using other features like the air conditioning.

    image.png

    https://tech.lennoxintl.com/C03e7o14l/VIu12Ch2uV/ehb_el180uhe_1904.pdf

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • 109A_5
    109A_5 Member Posts: 1,587

    Wiring diagram here

    https://www.questargas.com/ForEmployees/qgcOperationsTraining/Furnaces/Lennox_EL180UHE_IOM.pdf

    If I had to guess and it is not the blower motor, I'd say a relay on the board or a solder joint to the relay K5, K6 and/or K7.

    image.png

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • HVACNUT
    HVACNUT Member Posts: 6,298

    Is there fan if you switch the thermostat to fan on? That should be a different speed through a different relay on the board.

  • Ruffinitagain
    Ruffinitagain Member Posts: 3

    Thanks, folks! Great ideas

    Yes, that's the wiring diagram from the inside of the lower door panel.

    No, the fan doesn't go with the "on" setting (vice "auto").

    I will definitely try to get the fan going in cooling mode to help diagnose.

    I'd read somewhere that there might be a red button somewhere, in case of a trip condition, but didn't find it.

    Regards, ENR

  • Ruffinitagain
    Ruffinitagain Member Posts: 3

    and the fan turns real easy

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,388

    The red button is a thermal overload device on the motor. Most furnace blowers don't have those anymore. They have an overload but it is auto reset….no button

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