frying bottom contactor from inside furnace

by Kristi McCutcheon-Fortenberry
(Hartselle, ALABAMA, USA)

Nordyne E3 Series: the bottom contact is frying kind of like clicking in and out real fast. could u please help me on what the problem is or could be. thank you.

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Feb 01, 2016
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Contactor failures. NEW
by: Anonymous

I had this on my outdoor unit. Some idiot had decided to improve the indoor air handler by installing a second fuse in the wiring, and the push on connectors were loose. This added extra resistance to the 24VAC supply, and after 20 years it became critical and intermittent. It destroyed two contactors before I got lucky and caught it in the act.

The effect was that when the control logic decided to turn the contactor on, it drew about 1.8 amps from the 24VAC supply, and the voltage dropped to some low value, and this shut the logic down, so that the contactor de-energized about a tenth of a second after it had energized. Then the voltage rose again, and the logic circuit woke up and again energized the contactor. The poor thing was lashing back and forth 5-7 times a second, treatment that can be guaranteed to destroy it.

I removed the fuse and threw it away before shorting it out.

Check that you don't have any loose connections in the 24VAC supply wiring. The little push on spade connectors often need a gentle squeeze withpliers to help them get a grip.

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