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Douglas, HVAC Technician
Category: HVAC
Satisfied Customers: 3089
Experience:  Manufacture Rep for Major Brand, Technical Trainer, NATE
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Need help troubleshooting Goodman 100 furnace problems.

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My Goodman 100 furnace won't come on. The red light on the board stays lit (not blinking), the blower does not come on nor the ignitor heats up. Is there a reset button or something?

Let's eliminate the thermostat and the wiring first, just so we have a place to start.

Find the control board where the thermostat connects and jump from R-W and see what happens. You can make a jumper if you want to.

Customer: replied 6 years ago.

I made the jump from R to W and the furnace came on. My wife is very happy. What's next?

Well, this suggests that the thermostat is not working. Let's put it back as it should be, then remove the thermostat and jump the R-W at the thermostat subbase. If it works, then the thermostat itself is bad. If it doesn't, then we may have a broken thermostat wire. So let's try that next.

We'll have you going shortly.

Customer: replied 6 years ago.

I popped off the front of the programmable thermostat and jumped the R to W at the base but the furnace is not coming on.

Are there any unused thermostat wires in the bundle?

Customer: replied 6 years ago.

I have 4 unused wires at the back of the thermostat.

I am assuming you jumped it with the blower door back on at the furnace.

What we want to do, is pick two of these spares and we'll reassign them. So let's say, you have a spare black and brown just for giggles. Go to the furnace and make the black connect to the R terminal and the Brown to the W terminal and connect the black and brown together at the thermostat to see if this works. The power should be off for this. Once you make all the connections, turn the furnace back on and try it. If it works now, connect the Black to R at the thermostat and Brown to the W, just as you did at the furnace and see what happens.

Without a meter, I can't tell which wire is bad so we'll just do both.

Just be sure the power is off while you rewire and on, when you test. The blower door must be in place when you test (cuts the power).

Customer: replied 6 years ago.
I reassigned the wires at the furnace and connected the wires together at the thermostat but the furnace is not coming on.


Is there something like a zoning system on this furnace I don't know about?

Customer: replied 6 years ago.

No zoning or anything fancy, should I jump the R and W at the furnace again?

Yeah, that of course, is not a fix but it tells me the furnace is okay. The problem is in the external control circuits. At least, you can warm the house up, if nothing else.

Customer: replied 6 years ago.

I don't know if you got my reply so I am sending it again. Its all good now. I used the wrong wires from a wrong set of wires to reassign at the furnace. There were 3 of the same wire bundles at the furnace. One to the sump pump on the floor and the other 2 coming down from the ceiling. I switched with the other set of wires and the system is working even with the thermostat installed. Thank you for your help.

I replaced the blower motor and wheel couple of months ago. I had to use a generic motor mounting bracket (had no rubber bushing and the metal arms bolted straight to the wheel housing). There is a humming or vibration when the motor runs. Do you think adding rubber spacers between the bracket and the housing will help?

Do you have a condensate pump?

Customer: replied 6 years ago.

I think so. There is a pump motor and it's wired to the furnace and the condensation drain hose is hooked to it.

Sometimes the condensate pumps are installed with an internal float switch that breaks the power to the thermostat if the pump fails or say the termination of the pump freezes. You will want to see if the pump is full. If so, there is your problem.

I would look closely at the pump. If it pumps outside and it's cold, the tubing can freeze shut and the pump can't get rid of the water. The float switch trips and does just as you describe. Also, if the pump were to lose power or the pump itself fails, this switch shuts off the furnace. This would explain a lot here.

Customer: replied 6 years ago.

When the furnace wasn't working this morning, I noticed that the condensate pump was running non-stop. So I unplugged it from the wall outlet as I was checking the furnace. I just went back to the furnace to plug the condensate pump back up and found a puddle of water around the pump motor. I plugged the motor back and I can feel the motor running again. Any action required? Doesn't condensation occur only with AC and not heat?

No, 90+ gas furnaces produce condensate. Your pump is the problem. Follow the clear hose to where it terminates and you will likely find a blockage. In winter, these can freeze on occasion.

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