Coleman Evcon Fan motor

[ole]

Coleman Evcon Model DGAT090BDD Nordyne Fan 901998
When it gets cold weather out the fan shuts down for 5 to 10 seconds and kicks back on. After awhile a code comes on (4 flashes) signaling limit cycling. Sometimes it will come out of it and furnace keeps running. Other times the furnace shuts down and I have to switch off rocker switch and turn back on to start furnace back up. Tech said to replace fan motor as it felt hotter than normal. Replaced motor and ran good until cold weather (20 below) came back. Same thing with new motor. Cleaned off air cond evaporator and seems to be enough air coming out. Switched to "on" at the the thermostat instead of "auto" and everything is fine. Only thing is that the motor runs on high all the time. Could it be that I have a voltage problem going to low speed on the fan? Problem with circuit board? Thanks.

[Robert]

Hi,

You will need that Tech to test and see if there is a drop in airflow or an airflow problem.


With new motor, if airflow is ok, could just be a faulty limit due to weak contacts.


Locate the limit that is opening and when it does that, see if you have power to input sid eof limit. test from that side to ground.


If it's opening, then should have power still, which eliminates controls.

Then, if airflow is ok and temp inside chamber is ok, most likely a weak limit.


IF it is something other than a limit, a new limit would trip as well.



Thanks,
Robert