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Heating, Air Conditioning, Fridge, HVAC/Coleman Evcon gas furnace BGU07512A


My thermostat has a dial on it for cycle length, and I've had to play around with the thing to get the heater to start up several times. I don't know if the igniter or the blower starts first, but messing with that dial is no longer making either work. The igniter was replaced at the beginning of this year by the way. So right before it stopped working I heard a lot of noise coming from the blower I suppose. But I have heard it make noise like that before and then stop, but not this time. When I turn the temperature up on the heat like normal I can hear some quiet electric like noise and that is it. It won't do anything else no matter what I do. I should also mention that the safety door switch broke so I just put the 2 ends together with some black tape, and the green like came on with no error code as usual. But while I was doing that I noticed that the wiring that fits into a little connector thing that plugs directly into the furnace ignition control board was coming out of the connector. I bought the same kind of connector and replaced it. Then I plugged the heater back in, turned on the gas and turned thermostat up. Now the green safety light is rapidly flashing which I know means wrong polarity or twinning error, but I don't know how o fix it. Also before I replaced the connector the green light was working normally. Help me please.

The dial on the t-stat only adjust the amount of delay time the t-stat sends to the furnace.  It does not actually affect the operation of the furnace itself.  The more you keep adjusting it, the more likely it will get damaged.  It normally requires no more adjustment once set the first time.

Removing the door switch is not a good idea, and then to only connect the wires with tape is going to lead to a poor connection and could cause all sorts of other issues.

At this point you are going to have to use a multi-meter to check the system out do determine what is causing the problem. There is a certain sequence the unit follows when it goes to start.  I am not sure what connection is loose, as your description does not help me.  You may have a bad control board, which will have to be determined by troubleshooting with a meter. Make sure the inducer fan switch is opening and closing.  Check and see if the ignitor is good...  

Heating, Air Conditioning, Fridge, HVAC

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Craig HVAC Expert


I have been in the HVAC field for the past 18 years. I can help with most HVAC questions. I work on commerical buildings for the most part, and have yet to find anything I could not troubleshoot and repair, when repairable. I work on small 1 ton units to a 2500 ton chiller. Troubleshoot air flow, elect, and control problems. I attend regular classes to keep up with the latest and greatest.


I work on commerical sites, hospitals, gov't buildings. I can troubleshoot just about anything in the HVAC business.

5 years trade school, VFD training classes, Liebert factory training, some York and Trane factory training.

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