Limit switch open DGAA077BDT

[txMark]

I have a new DGAA077BDT unit that is giving me 4 lights. Note this unit has never ran a full cycle. Coleman had me bypass (temporarily) the lower limit switch by jumpering the wires, and it still gives the same error. It will startup and light with the flame as it should, then immediately after the blower comes on it turns off the flame. I have checked the ground and the board has even been replaced. I am sitting at a roadblock, is there anything else I can try to prove out a particular part?

[Robert]

Hi,

All you can do is test entire ignition circuit from beginning to end to see if anything is wrong.

If all is ok, that rules out electrical, so then look for blockages, anything apart from norm, ect. .


Check flues/roof-jacks, check burner orifice for spider/web, check blower speed, down drafts.

Check position of ignitor and flame sensor (if only an ignitor, it is your flame sensor too).

If you have a seperate flame sensor (haven't checked book on your model), then it may need cleaning with steel wool (metal only, check ceramic shroud for cracks).


If none of that finds problem, then a Tech with diagnostic equipment will need to be called.



Take care and best wishes,
Robert

[Robert]

If there is a limit opening or you find an open limit after this happens, find reason for limit opening.

Could be faulty limit.


Thanks,
Robert

[txMark]

Thanks Robert. This unit is about a week old and has experienced this since day 1, the circuit board was replaced just in case, so I guess if it is deeper than that we need to request another new unit. I thought surely it would stay lit after the limit switch was bypassed, but it still keeps trying and goes out after about 8 seconds of flame (blue flame) which leads us to a flame sensor or pressure switch? I guess the smart thing to do is get the series 4000 roof jack installed first to make sure it isn't causing my issue.

[Robert]

You don't have the roof-jack installed ?



Thanks,
Robert

[txMark]

We have a roof jack that was replaced previously, but was not a 4000 series. I have heard two stories, one it shouldn't be the cause of this, and one it will cause this!

[Robert]

It may or may not be cause, but without correct roof-jack, you will not know.


It will not work correctly without the manufacturer's recommended roof0jack, so have that installed and go from there.

Was it installed by a licensed Tech ?


Is the unit brand new ?


Thanks,
Robert

[txMark]

Bingo, was the roof jack! Sheesh Lol.

[Robert]

Thanks for update, glad it is good to go now.


Take care and best wishes,
Robert