Gas and Oil Home Heating Furnaces - help with Miller gas furnace

I have a Miller gas heater in a mobile home. I am assuming the heater is the original ; mobile home is a 1983. The heater is kicking on fine but it is not blowing warm air out of the vents. Help...I don't know what the problem may be

Assuming the blower is kicking on, is there any air coming out of the vents or is the burner firing without the blower?

The blower comes on only when button is pulled out on "manual"...air is coming out of vents (not hot) ...can't get burner lit

Is the furnace in question a model MOC_ _ AG?

the model # is CMF80/AG

The AG is the important part. This burner has a pilot which stays lit all the time. Is it lit? If not, will it light & stay on? If it will light but not stay on, you probably need a new thermocouple.

The pilot light is staying on; i can't light burner...do you pull the pilot gas valve out to start burner?

I replaced thermocoupler...if the spud orifice is clogged w/ soot will that stop the burner from lighting?

:wall: I replaced thermocoupler...if the spud orifice is clogged w/ soot will that stop the burner from lighting?

It sure will. Make sure you have 24 volts going to the thermostat. No 24v, no main burner. The pilot does stay lit, does it not?
Note: When checking for 24v at the thermostat, the furnace door needs to be closed & latched.

I have 24v..and pilot does stay lit...i cant get burner lit...and i still have to set the time delay for it to click on and off

There is no time delay on a CMF. Does the main gas valve click when you turn up the thermostat? It could take a few seconds, maybe up to a minute.
If it does not, remove the wires from the gas valve & check for continuity across terminals mv/pv & mv.

i have taken the oriface off and it was not clogged up...on the instructions inside the furnace...it talks about pushing a red button for 30-60 secs to ignite the pilot...but there is no "red" button.. i am manually lighting it...after I light it...it does stay lit...
When I turn the thermostat up...I don't hear a clicking on the furnace...the blower will come on...if I push the button in for "manual"....but the burner is not lit..i pull out the black button that says "on/off pilot" to try and light the burner...but it will not light.?????????

and i did check for continuity for both 24 & 120 v...I have all power

On the gas valve, there is a knob. On or next to it there should be markings: OFF, PILOT, & ON. this knob needs to be in the ON position for the main burner to light.

it may possible that your thermostat maybe failing, however, you say that if you turn it to Fan on, the blower comes on. If you have tried everything possible, then it maybe time to get a repairman out to your mobile home to look.

does the burner gun combustion motor run?is it running properly.this motor has a centrifugal switch that activates the gas valve.if the motor is not turning the correct rpm the switch will not activate the gas valve.if the combustion motor does not run check the power outlet.is there voltage there?if not check the door switch and the temp limit switch located beside the blower assembly.if the combustion motor does run you can check the manifold orifice.in my experiences i have found this is a nice place for spiders to live.hope this helps

does the burner gun combustion motor run?is it running properly.this motor has a centrifugal switch that activates the gas valve.if the motor is not turning the correct rpm the switch will not activate the gas valve.if the combustion motor does not run check the power outlet.is there voltage there?if not check the door switch and the temp limit switch located beside the blower assembly.if the combustion motor does run you can check the manifold orifice.in my experiences i have found this is a nice place for spiders to live.hope this helps

What you describe is not applicable to the AG models, you are thinking of the PG models. AG - atmospheric gas, PG power gas. The atmospheric burner does not have the motor, centrifugal switch, etc.

To the OP, one thing to check, which is very common is to make sure the furnace door is FIRMLY closed. There is a door switch that if the door is not closed properly the burner will not fire.

Hey guys, this thread is over 3 years old.

DOH!!!! :wall: :thumbdn: :thumbdn: :wall:

Hank, trust me, wecome to the club. I've done the same thing myself. :o