I have attempted resetting the furnace a few times, each time it lights for about two seconds and then goes out. It repeats the process two more times after that but only without igniting. Then the diagnostic light starts flashing and remains flashing until reset. I know because I sat there and watched for twenty minutes to see if I could get a pattern I could pick out, and no by the way I couldn't.

Is possible you have a bad flame senser

is possible you have a bad flame senser

It can be cleaned with fine sandpaper or steelwool

Any idea on how to get to it?

Do you have a parts or info sheet on the unit, if so look it over the parts should be labeled,I` m not sure if a coleman has a flame senser, not knowing how old the furnace is

Well the papers have copyright dates of 2001 and its under Red T products If that helps any. But I found the parts list, I'm not seeing anything for a flame sensor.

During the ignition sequence, can you see a glow through the small window above the burner?

Yes I can.

Yes I can.

I'm not sure but that furnace might use the ignitor as the flame sensor. Some do but some have a separate flame rod. Look on the control module to see if there is a wire connected to a terminal marked "sense" or "sensor". If there is such a wire, trace it to the other end. It should be a porcelain rod with bare metal rod sticking out the other end. Remove that rod, clean it with a scotch brite pad, reinstall & try the heater again.

All right I'll try that. Thank you. I'll let know the conclusion or if there is. Lol

All right I see a wire for a sensor rod. And says something about it having a "hot surface ignitor".

Alright I see a wire for a sensor rod. And says something about it having a "hot surface ignitor".

There should be two terminals or a plug for the Hot Surface Ignitor (HSI) & a separate one for the sensor. Is this the case or not?

There are two separate wires. The yellow wire leads the sensor rod.

Remove the sensor & clean the metal part which sticks into the flame with scotch brite, very fine sandpaper, or steel wool. Reinstall & try the furnace.

So I got to remove the entire module? If so it looks like the pipes have been cemented in.

So I gotta remove the entire module? If so it looks like the pipes have been cemented in.

No, not the module, maybe the burner, but they are super easy to remove. You may need a new burner flange gasket. I honestly don't remember what the burner assembly looks like on that particular furnace. A few pictures would be helpful.

I wish I could post pictures Grady, but I'm doing this from my phone so the only I can do pictures is through email or something like that.

I wish I could post pictures Grady, but I'm doing this from my phone so the only I can do pictures is through email or something like that.

Try tracing that sensor wire to the burner. You may be able to figure out how to remove the sensor. I did a search for your model number & found an installation manual but the pictures weren't much help.

Yeah, I thought the same thing. I've followed the wire to just beside the module. I can't figure out how to get it out past that point without pulling everything. I don't want to end up pulling that wire out and end up breaking something.haha

Yeah, I thought the same thing. I've followed the wire to just beside the module. I can't figure out how to get it out past that point without pulling everything. I don't want to end up pulling that wire out and end up breaking something.haha

Don't pull on that wire. Here is a link to the installation manual (with a parts diagram) http://homeappliance.manualsonline.com/manuals/mfg/york_a_johnson_controls_company/dgah056bbsa.html?idRes=15054123

Is the gas line piped with steel pipe or is there a flexible line? If piped with steel, there should be a shut off valve & union to aid in disconnecting the gas from the burner.