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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8136
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a 17yr old Goodman unit with propane backup. It had

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I have a 17yr old Goodman unit with propane backup. It had been cooling fine all summer, then went a few week mild spell where I don't think the cooling came on at all. Now tried heat but nothing. You can hear some humming under the house where the air handler is, but blower does not kick on and outside unit does nothing. If you put it in emergency the blower will come on, but still no heat, not even propane. Put it back to cool and it seems to be fine, with outside unit running and cold air out the vents. Any ideas?
Welcome to Just Answer!

The low speed fan motor winding may be bad, that would allow the fan to run in cooling mode, and in 'FAN ON' mode but not in heating mode.

A bad fan relay will also produce that result. Unless you are very competent with electrical circuit diagnosis and have the necessary test instruments, this is something you will have to call an HVAC service company in to repair.

Let me know what you want to do. If you want me to help find a good service company tell me which direction you are from the center of the nearest city and i will see who I can find with good reviews near by.

Customer: replied 3 years ago.

I assume that's the main motor in the air handler? The blower motor was replaced earlier this year, so presumably has some warranty - will check. I'm reasonably competent with basic electrical, replacing circuit boards, etc. If not the motor, is the fan relay a reasonably affordable part I can just replace and gamble on it fixing, skipping the diagnostic step or paying yet more money servicing this old thing?

Hello again, your presumption is correct.

17 years ago we were still transitioning from use of $10 fan relays, to mounting the fan relay on the $200 control board.. those relays are not individually replaceable, you have to replace the entire control board.

I am however not sure at all on the diagnosis. We need to take a closer look.

If you can buy a clamp around type amp meter you can check the amperage draw on all 3 or 4 wires attached to the fan motor when it is running properly in cooling mode, and when it is not running and just humming.. that will tell us a lot.

$60 or so at a big box hardware department.

Let me know, we can go from there.

Customer: replied 3 years ago.

As follow-up feedback, the answer turned out to be a poor connection on one of the thermostat wires under the house, resulting in a low voltage signal for heating. The tech had a helluva time finding it, but he did, and I was only charged their $89 diagnostics charge so was very happy to get off so cheap. Your feedback was helpful, though. Thanks.

Save that guys business card! He is a good one!

I will post my comment here as an answer so that if you feel like rating my feedback positively you can do so. Otherwise just ignore it.


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