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How is it going? I just moved into a place I bought. It has separate AC units for both floors. We started having an issue with one of the air handler units. One night when turning the air on the outside AC unit turned on but the air handler unit never kicked on. Next day while at work an HVAC tech came out and told my wife he messed with some wires and it kicked on. Well, since then it has stopped twice again. I went into the attic and was messing with the wires but all seemed fine. I happened to touch the top of the motor with a screwdriver and it kicked on. Thought to myself well maybe there was a loose wire and it may have just gotten the signal to turn on. However, tonight while troubleshooting again I took off the cover and again touched the top of the motor with a screwdriver and wouldn't you know, the unit kicked on.

What in the world could be the cause of this? Some sort of ground issue?

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    I would contact an electrician. There is something funny happening.
    – Ruut
    Nov 1, 2015 at 6:23

2 Answers 2

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I had a similar issue and could have sworn it was mechanical/electrical. I had a service man come in and he removed the air filter from the handler. It started right up afterwards (i am unsure if there was a reset switch he had to trip). He mentioned that my air handler will shut off if there is a great enough pressure difference between the supply and handler sides of the filter. Never thought of that but worth a try before you spend the monies!

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If you can repeat these results with a non-metallic object, I'd say the capacitor and/or the bushings are burnt out. I think it was your tapping on it, that helped it overcome the physical resistance keeping it from spinning. That's assuming "messing with the wires" also jostled the motor into spinning, instead of the problem being a lose wire all along.

The problem is, that if walking up to it and banging on the furnace makes it work, it could be either. If the trick only does work with a screwdriver, proceed with caution or contact a better HVAC guy.

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  • If it does it again I will try out another object. I hardly even touched it with the screwdriver when it kicked on. Don't know if it pure coincidence that both times it happened to kick on at that moment or what. BY the way this is a complete electrical system, no gas, dunno if that matters. Anyone have a link to testing the components in an air handler unit? Nov 1, 2015 at 16:50

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