Coleman furnace is posessed... - http://www.hvacmechanic.com/ Forums
Original message
| neowolfwitch
 |  "Coleman furnace is posessed..."
, posted Wed 23 Apr 12:59  
I've had an HVAC specialist out for two nights now trying to fix this problem, and we are both stumped (I have limited repair experience myself- replacing ignitors, relays, and motors)...
The combustion booster comes on, ignitor comes on, burner lights. About 15 seconds later- burner shuts off for no apparent reason.
Tried two new burner flame sensors.
Tried two new controller boards.
Tried new combustion booster/centrifugal switch.
Tried new gas valve.
Controller diagnostic LED has a single flash, indicating "Ignition Failure", even though burner is lighting with a strong blue flame, and ALL of the flame sensors tried are working. Once again- this is with three different control boards- the original and two new ones.
What else could it possibly be?
Thanks in advance for any advice. At least this happened in the Spring, instead of the middle of Winter.
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Replies:
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| hvac101
| "Re(1):Coleman furnace is posessed..." , posted Wed 23 Apr 19:48:
what is your micro amp reading? make sure all the ground connections are tight and try adding another one.
[this message was edited by hvac101 on Wed 23 Apr 19:49] |
| acefurnacefxr
| "Re(1):Coleman furnace is posessed..." , posted Wed 23 Apr 17:58
bad or weak transformer......are you monorting the voltage at gas valve while this is happening?
HVAC REPAIR IS NOT A DIY WEEKEND PRODJECT
I have been performing HVAC repairs for 23 years
http://www.hillaryclinton.com
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| | tom446
| "Re(2):Coleman furnace is posessed..." , posted Wed 23 Apr 19:48
Heres a coulpe of thoughts.
Is your Polarity Right ? Do you have a good ground ? What kind of reading are you getting off the flame sense rod ?
If in doubt call a pro !
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| | yuri
| "Re(3):Coleman furnace is posessed..." , posted Wed 23 Apr 21:38:
Ace is right. Put your meter on the gas valve to see if the voltage is dropping out. Should have 24 volts. Usually a flame failure/dirty sensor/weak signal drops out in less than 5 seconds. Make sure the front of the burner is clean. The current passes from the flame sensor thru the fire thru the burner back to ground and the board. Get your tech to pull out the burner and carefully inspect the back of the heat exchanger slightly above the burner level for cracks. Had an inshot type that split wide open there.
Yuri
[this message was edited by yuri on Wed 23 Apr 21:41] |
| | mechacc
| "Re(4):Coleman furnace is posessed..." , posted Thu 24 Apr 10:38
Hmmm. I take it this is a Coleman manufactured home furnace? 15 seconds operation indicates that the system may be starving for combustion air. Since spring is here I would take the roof jack cap off and look for debris or possible birds nest. If not there don't put the cap on until the combustion blower is removed. If there is debris on the wheel that is the source of the problem. Also inspect the inside of the combustion air chute at the furnace for any other debris.
MechAcc
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| | tom446
| "Re(5):Coleman furnace is posessed..." , posted Thu 24 Apr 19:13
Mechacc may be on to something. Most mobile homes have a 2 pipe vent. I've seen the inner pipe start to rot out on them. This allows the combustion exhaust gases to mix with the fresh combustion air which starves the fire for oxygen puts the fire out. In most cases the fire will light but then go out after it uses up the oxygen that is in the heat exchanger. Watch the fire burn. As it runs out of oxygen, the nice blue flame will go to a deep ugly purple color and the flame normally starts rolling.
If in doubt call a pro !
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