Armstrong furnace "sticking" on - a bump turns it off ???


Old 09-29-19, 01:44 PM
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Armstrong furnace "sticking" on - a bump turns it off ???

Armstrong model: MCE42 series AC furnace with three heater elements and two 120vac sequencers

Ran fine for years, but recently the fan and heaters often remain on after going over thermostat setting. Applying my USAF tech training, I discovered knocking the side of the furnace would immediately shut if off when it was running over.

So I opened up the control panel, let it run over thermo setting and started by tapping the main solenoid - no effect.

I then tapped the 1st sequencer, voila! It shut down.

But then when I tried on subsequent attempts it did not work, and tapping on the second sequencer seemed to work Sigh...

The sequencers I see being tested on Youtube are 24v and not as complex as mine, which have both fan and heater contacts (see attached pic).

These sequencers are "discontinued" on line and rebuilt units cost ~$175. We are poor so I can't afford to take chances on just ordering w/o knowing for sure it is bad.

So my questions:
* do you think I am on the right track here?
* are these sequencers known to sometimes begin sticking?
* how can I test them for a sticking solendoid?

Any help on this would be VERY APPRECIATED!!!
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Old 09-29-19, 02:00 PM
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If you think they are bad or you tap on them and they shut off...... replace them.

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