Coleman Evcon blower problem mod. DGAT070BDE

[rmhguy]

Hello,

I am trying to help a friend that lives 75 miles from me with a furnace problem. I’m trying to get as much information as possible before I make the trip to try to help her.

The furnace involved is a Coleman Evcon, model DGAT070BDE, Serial number 980653255, BTU input 70,000, BTU output 57,000. This is a wall mounted furnace in a mobile home. While the furnace is about 10 years old it has only been used for about 3 years.

The problem is intermittent, however it happens often. The furnace comes on just as it should and shuts off when it heats the house to the temp. set on the thermostat. This part is working fine. At times, after the burners and blower have turned off the blower (only the blower) will turn back on and after a few minutes will shut off. The blower may cycle on and off like this several times before it shuts off and stays off. Once the house cools down far enough the burners come on and then the blower. It runs until the correct temp. is reached and shuts off. The blower only may or may not come back on and off. If it does come back on it will usually cycle on and off (several minutes) for 2 to 5 times before it shuts off and stays off.

I’m not a furnace repair person but do have some knowledge of their operation. I’m guessing that the problem may be the high or low limit switches.

Does anyone have any suggestions or test procedures I can follow to isolate the problem

Thanks

[Robert]

Hi,

See if she has taken care of this first :

http://www.dgatprogram.com/index.asp



Then tackle the blower problem.


Most common would be a bad fan switch, control board or dirty heat chamber.



Thanks,
Robert

[rmhguy]

Thanks Robert,
I ran across the furnace recall yesterday looking for information on this furnace. She is calling to get the recall done this morning.
The recall says this model furnace can overheat. Maybe it is overheating and when the blower shuts down there is enough residual heat to cause the blower to cycle on and off 2 or three times until the furnace is fully cooled down. It’s just a thought since the trouble code light is “steady on”, and not flashing indicating that the furnace is working properly.
The wiring diagram on the cover does not show a part called a “fan switch”. It does show a high limit switch and a low limit switch. Would the low limit switch be considered the fan switch?
I’ll let you how things turn out after the recall is done. Thanks for your help. Bob

[Robert]

Hi,

The control board controls the blower operation for that furnace. It doesn't have a fan switch.


I listed both because I was more concerned on her getting recall done first.



Thanks,
Robert