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Ignition failure
I have customer with a Coleman Evcon furnace AT075BDC. I have tried numerous parts and called other technician friends out to look at the furnace…. No one can come up with anything that works. Here is what happens.

The furnace has a total failure. When this happens the electronic module shows a green flashing light 1 repeating flash. The induction motor runs and runs. Nothing else happens…. The house just keeps getting colder. If I re-start the system by killing the power, the following happens.
1. The thermostat calls for heat
2. The induction motor runs for about 11/2 min.
3. The igniter glows for about 30 seconds
4. The gas valve opens
5. The burner comes on for about 13/4 min.
6. The gas valve turns off and the blower motor never even tries to run
7. The induction motor runs for hours and nothing else happens, the house gets cold.
8. I turn off the power for a moment
9. I turn the power back on and the cycle repeats exactly. Sometimes it works on the first try and sometimes it takes several tries.
10. On the final try, the cycle repeats but instead of step 6 the blower comes on and the furnace lives again. Sometimes it will work for several normal cycles before the pattern repeats then the failure happens again. Occasionally the igniter will not even come on and then there is the same failure. Sometimes everything works perfectly for a week…. Then the failure starts all over again. Step 6 happens…. I skip to step 8 and after several tries… it works great again for several days or possibly for only for a few normal cycles….You get the idea.
All that being said…. Here is what I have replaced, not necessarily in this order.
A. The thermostat
B. The electronic module
C. All 3 of the fan limit switches
D. The 2 relays
E. And the induction motor with a centrifugal switch in it.
F. The filters
The only thing I haven’t replaced is the transformer.

I am hoping that there is someone out there that might have an idea as to what will correct this issue, I am really tired of dealing with this customer.
All the best,
Dean
 

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Ignition failure
I have customer with a Coleman Evcon furnace AT075BDC. I have tried numerous parts and called other technician friends out to look at the furnace…. No one can come up with anything that works. Here is what happens.

The furnace has a total failure. When this happens the electronic module shows a green flashing light 1 repeating flash. The induction motor runs and runs. Nothing else happens…. The house just keeps getting colder. If I restart the system by killing the power, the following happens.
1. The thermostat calls for heat
2. The induction motor runs for about 11/2 min.
3. The igniter glows for about 30 seconds
4. The gas valve opens
5. The burner comes on for about 13/4 min.
6. The gas valve turns off and the blower motor never even tries to run
7. The induction motor runs for hours and nothing else happens, the house gets cold.
8. I turn off the power for a moment
9. I turn the power back on and the cycle repeats exactly. Sometimes it works on the first try and sometimes it takes several tries.
10. On the final try, the cycle repeats but instead of step 6 the blower comes on and the furnace lives again. Sometimes it will work for several normal cycles before the pattern repeats then the failure happens again. Occasionally the igniter will not even come on and then there is the same failure. Sometimes everything works perfectly for a week…. Then the failure starts all over again. Step 6 happens…. I skip to step 8 and after several tries… it works great again for several days or possibly for only for a few normal cycles….You get the idea.
All that being said…. Here is what I have replaced, not necessarily in this order.
A. The thermostat
B. The electronic module
C. All 3 of the fan limit switches
D. The 2 relays
E. And the induction motor with a centrifugal switch in it.
F. The filters
The only thing I haven’t replaced is the transformer.

I am hoping that there is someone out there that might have an idea as to what will correct this issue, I am really tired of dealing with this customer.
All the best,
Dean
Thats a lock out you're describing. It will only try and relight so many times (On most furnaces) before it does that. It brings on the fan so the owner knows they need to call someone.

Try cleaning the burners. The issue is that the ignitor is not lighting off the burners.
Also, I would put my manometer on the valve manifold and be certain the gas pressures matches what the dataplate calls for them to be. This way youre not guessing if gas actually is flowing through the valve.
Simpler yet, before doing any of the above, check and be sure the gas is turned on to the unit.
 
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