Goodman GMT Fan Issues

Problems related to residential installations.

Goodman GMT Fan Issues

Postby Harley99103 » Sun Sep 25, 2011 1:46 am

Lost and thinking its the board but want to make sure.

Work up one morning and the fan was running, went to thermostat to turn fan off would not turn off. So went to furnace checked the light and soild red (normal). Was in a rush so just flipped the main power switch. Turned in back on the other day and fan was on turned off waited 2-3min. turned back on and fan was trying to turn but would not. So turned off, tried again in an hr or so, nothing.

I immediatly went to Thermostat and took the wires off held them together. Then waited 5min or so after I reset the unit nothing

While at the unit I can hear a relay on the board click

Ohm'ed out motor leads to the motor case no continuity , then lead to lead 5ohms

Has 4vac on the Neutral wire when I have the thermostat wires touching and push in the door switch

Jumpered R and G on the board nothing

If someone can point me in the right direction that would be great

Thanks
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- Goodman GMT Fan Issues

Postby 4ftBanger » Sun Sep 25, 2011 10:11 am

I would probobly rule out the thermostat and wiring because you eliminated the thermostat from the equation and don't get consistent symptoms... - sometimes fan runs all the time, sometimes won't start when it's supposed to. We can also likely rule out safety switches because no errors are indicated by the furnace control board.

Based on your description I'd say it's likely a bad fan relay on the control board - Contacts might be getting pitted and they stick sometimes and not make a connection other times. These little black relays are part of the furnace control and, in my experience, are about a 6-8 year part (sometimes less)
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- Goodman GMT Fan Issues

Postby Harley99103 » Sun Sep 25, 2011 11:32 am

Thanks, for the input. Thats what I was thinking it was going to be but wanted some input. I tried to follow the board wiring to see what relay to meter that relay when I flipped it on, but was to confusing. I found an OEM board new for 90bucks so I think that is what I am going to try. I also tried to tap the relays but still nothing. When the fan is running normal operation I should be getting 115vac on the lead right?

Thanks Again for the Help
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- Goodman GMT Fan Issues

Postby 4ftBanger » Wed Sep 28, 2011 4:21 pm

You should have speed taps on the board next to the black relay cubes. They are typically labelled heat and cool - when the relay closes you should have appx 115vac from the speed tap to ground or neutral (L2)
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- Goodman GMT Fan Issues

Postby Harley99103 » Wed Sep 28, 2011 4:37 pm

Thanks for the input, replaced the board and works like a charm.
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