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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a furnance in my mobile home. Model DGAA077BDTA and

Customer Question

I have a coleman furnance in my mobile home. Model DGAA077BDTA and we have a steady green light and one blinking red light which indicates a ignitor issue. Can someone assist?
Submitted: 11 months ago.
Category: HVAC
Expert:  BillyHvac replied 11 months ago.

hello,

do you ever see a glow or 3 seconds of flame?..or nothing?

Customer: replied 11 months ago.
I saw an orange glow and blue flame for 3 sec or more
Expert:  BillyHvac replied 11 months ago.

ok, in front of the burner is the ignitor and also a flame sensor.

We need to clean the flame sensor with steel wool...shown here

Customer: replied 11 months ago.
Where is the flame sensor? The diagram is not very clear as to where it is located and how to reach it. Do I need to unscrew something to reach it?
Expert:  BillyHvac replied 11 months ago.

you see where the glow is?

That burner gun must come out.

It is a bit tedious on this model..but the flame sensor is where the flame comes out.

Customer: replied 11 months ago.
is it the circular unit that has screws all around it? Do I need to unscrew it all and drop the whole unit out?
Expert:  BillyHvac replied 11 months ago.

Correct....gas valve shuts off, undo gas pipe....remove screws...pull assembly straight out...

Clean the sensor and install..

Customer: replied 11 months ago.
Ok.....used steel wool on flame sensor. Honestly, it did not look bad at all. All put back together. What is the correct procedure to test? Turn on gas, flip on electric, then what? Do I need to go thru the recycle process again?
Expert:  BillyHvac replied 11 months ago.

Turn on gas, turn on electric, turn thermostat to heat and up.

May take 2 cycles...the flame sensor gets a clear glaze and this must be eliminated before moving forward.

Customer: replied 11 months ago.
Done, but we still have a steady green light and a blinking red light. Is this OK?
Expert:  BillyHvac replied 11 months ago.

I apologize as I lost connection..just a moment.

Customer: replied 11 months ago.
Update....I switched the light switches on the box to the down position and there is a steady green light. Is that the position the switches should be in?
Expert:  BillyHvac replied 11 months ago.

steady green is good...it means normal...have you tried furnace again?

Customer: replied 11 months ago.
once, orange glow, no flame. Waited 5 minutes and trying again.
Expert:  BillyHvac replied 11 months ago.

make sure all gas back on....and gas supply to other appliances...

Customer: replied 11 months ago.
Ok...this is what happens....the orange glow comes on, the flame comes on, but the minute the fan kicks in the flame goes out. We still have a green light
Expert:  BillyHvac replied 11 months ago.

so the flame last until the time blower kicks on....as soon as blower kicks on the flame goes out?....Or does the blower kick on..flame starts to waver/dance then flame goes out while blower still running?

Customer: replied 11 months ago.
Well, now I notice the flame is back on and is staying on. Just waiting to see if warm air will start blowing. It always takes it a bit to start throwing out warm air. Stay tuned....
Expert:  BillyHvac replied 11 months ago.

standing by

Customer: replied 11 months ago.
It should be throwing out warm air by now, but still not. Everything seems to be operating fine. Is there anything else to check? Blower, flame all OK. Does the cover need to be on to operate correctly?
Expert:  BillyHvac replied 11 months ago.

yes put covers on...is this propane?

Customer: replied 11 months ago.
We put the covers on....no propane. It's gas
Expert:  BillyHvac replied 11 months ago.

if the gas is on...(burners) and the main blower....and there is little heat....then there are:

ductwork apart

low gas pressure

Customer: replied 11 months ago.
I don't believe it would be low gas pressure....we have had no issue with that. I'll check under the house for ductwork. We are getting air blowing thru the vents though....
Expert:  BillyHvac replied 11 months ago.

well it is now a matter of the combination of things.

We have burner

We have blower

So the 2 things we need to deliver heat are present. So there is a deficiency in air flow (duct), dirty blower wheel, plugged ac coil (if present) or the heat in exchanger (gas pressure)

Customer: replied 11 months ago.
Ok..another new wrinkle. The furnace went off (we have it set on auto at 75 degree, but it is only 67 degrees). We are changing the batteries in the thermostat....ugh.
Customer: replied 11 months ago.
The batteries on the thermostat were bad, so we replaced and the furnace is back on. Still tepid air...not warm. Is there another heat sensor somewhere? I think it is detecting that the temperature is in the house is fine, when it is not.
Expert:  BillyHvac replied 11 months ago.

The only thing that detects temp is the thermostat.

All temp detectors in the furnace are simply limits that cut off if the furnace were too hot.

Customer: replied 11 months ago.
the furnace turned itself off again. Stumped.....why is the furnace turning off when it has not reached the desired temperature. We have it on auto...so it should be maintaining the temperature (we have it set at 81 degrees now just to see if it will get warmer).
Expert:  BillyHvac replied 11 months ago.

Remove the thermostat....take the wire on R and the wire on W and twist together.

Tell me if furnace runs nonstop, or turns off.

Did we check the blower wheel yet to see if clogged or if ac coil is plugged?

Customer: replied 11 months ago.
They are twisted together, but the furnace is not blowing. Is there any possibility that it could the thermacouple?
Customer: replied 11 months ago.
Ok....the furnace kicked on and it is running
Expert:  BillyHvac replied 11 months ago.

my guess is there is an air restriction, dirty blower wheel, plugged ac coil, plugged filter...something is restricting the air flow.....furnace overheats internally....shuts down...cools and trys again..

Can you check the inside of the blower wheel or post pics?

Customer: replied 11 months ago.
where is the blower wheel?
Expert:  BillyHvac replied 11 months ago.

top section...this is a mobile or modular home install?

Customer: replied 11 months ago.
we have a manufactured home
Customer: replied 11 months ago.
Should we untwist the wires now?
Expert:  BillyHvac replied 11 months ago.

the main blower is behind the upper grill in door. Where the filter goes across door...the blower is behind it.

Customer: replied 11 months ago.
The blower is turning fine, does not look dirty at all. However, the motor had lint/dust all over the back of it. I have vacuumed it out and trying it again.
Customer: replied 11 months ago.
The furnace turned off again...apparently that was not the issue. Where is the AC coil?