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Bad primary relay or motor switch?

colyer Member Posts: 1
Howdy, and thanks for any ideas... Beckett af60xn on a Ruud forced hot air furnace, circa 1978. New cad cell, electrodes, nozzle, filter and screen. Lockouts every few days; no pattern. On reset, no flame UNLESS contactor relay first closed and released once by hand (main power off first), OR air squirrel cage rotated a few degrees. The first makes me think bad relay or electronics, the latter open winding or bad centrif switch. Being lazy AND cheap, thought I'd ask before replacing both.


  • Big Ed_4
    Big Ed_4 Member Posts: 2,806
    If it would not run less you rotate the motor you have a bad high spot in the motor . you can check a split phase motor for high spots with an OHM meter . should be around 3 ohm , turning the motor and lifting if it hits 7 ohm its an hight spot . But just turning and it feels loose then it runs is due . Really I should tell you ,the whole furnace is due . Any furnace built after 1963 and its over 20 years (except an Thermal Pride) I would bet a bag of donuts there are holes in the heat exchanger. Good luck with it

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  • billtwocase
    billtwocase Member Posts: 2,385
    I would say burner motor, but I wouldn't agree that the age necessarily warrants replacement. I have multiple Thermopride, Rheem, Texaco, Williamson, Air Ease, Olsen, Friedrich, Lennox, Mueller, and so on that are still in service, and are inspected yearly for holes, cracks, etc. Thorough cleaning, and combustion chamber integrity are key in their survival. Now the Rudd, Unicell were not that well built 80's up. I think Ruud in 78 was a rebadged Ducane? Any pics?