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I just bought this home in June, and I imagine the thermostat has been off since early Spring. I don't know the furnace history, but it's a Coleman Evcon DGAT090BDF, and it won't ignite. When the thermostat is turned up, the ignition control box just hums. Any experience with this? Thanks!

What is the diagnostic light flashing ? Rectangular upright metal control box will have a green light visible through hole.

Is it flashing and if so, how many flashes ?

Should also have a flash code nearby or on the box for you to get idea of problem.


Will be back on later tonight.


Thanks,
Robert

When you first start the furnace, does the booster motor run? That's the small motor to the side. You can usually hear it.

Otherwise have to narrow down the problem to a part inside that box, like perhaps the transformer. I'll let Robert walk you thru that.

Mark

Sorry. I forgot to mention the light. It is a steady green--no flashing. When the thermostat clicks on, the booster motor does not start either--nothing but the hum from the rectangular box.

Thanks for your replies, Robert & Mark.

Hi, Open the box and see if the hum is from the transformer.

With a steady green light, you would be getting power.

Check transformer connections, make sure they're tight .


Set t-stat to Fan ON Continous and see if the blower motor only comes on and runs.


Headed out for sure now, be back later tonight.



Thanks,
Robert

I checked the connections & they are tight, but now the green light flashes three times in sequence.

That would indicate your pressure switch is not closing. Is your booster motor that Mark mentioned in above reply running ?

It should start up within 2 -3 seconds of call for heat from t-stat.


Either it isn't running, is running too slow, air pipe is open, crooked or blocked, pressure switch is faulty, the two small hoses connected to pressure switch is clogged, torn or damaged.


ALL of those will cause pressure switch to not close, which will keep burner from igniting.


Take care and best wishes,
Robert

I replaced the pressure switch, and I'm still having the same problem (light flashes three times & no motors kick on). Any other ideas? Thanks.

If you've replaced the pressure switch and the booster motor is not running when the thermostat calls for heat, then you need a new booster motor. Part number for your furnace is 7990-314P, which can be seen and ordered from this page: http://www.mobilehomerepair.com/ColemanGas.html

Mark

Thanks Mark! Will any special tools be required to separate the motor shaft from the fan and then attach the new motor?

You will probably need an allen wrench. If all goes well, the wheel will slide off without too much trouble. Work carefully as you can't buy the wheel by itself. You ruin the wheel, then you have to buy the whole assembly.

Mark