Coleman Evcon DGAT070BDD blower runs constantly

[chasvez]

Hello!
I have a problem that has been going on since last winter
My problem is, when my furnace first kicks on for the first time; everything works fine. Once the temperature reaches the desired setting, the blower turns off then kicks right back on blowing cold air. this will continue repeatedly with out end. The board also shows a no call for heat error during the repeated cycles. If I turn off the rockerswitch, turn up the thermostat, and turn on the rockerswitch, the furnace will operate again blowing hot air until temp is reached but a no call for heat is still flashing. Also in the summer running A/C a similar problem occurs but only cycles for two or three times then turns off till it needs to recooled if i remember right. a heating and cooling guy GLANCED at it when he replaced our heat exchanger (recall I found out about on your site that I had no idea about! thanks for that) and thought he had it fixed with a loose wire but no joy. If I could have some advice on what to test and how I have a multimeter and am savoy, but unfortunately have little money to pay alot for service and barely for expensive parts so the more I can do the better. Hope to hear from you soon and thanks in advance.

[Robert]

Hi,

That is about impossible for me to diagnose from here.


In BOTH heating and cooling modes, the indoor blower motor is energized/controlled by the circuit board.


The board could be faulty.


For heat, if t-stat is satisfied and there is no call for heat (0vac reading across W and C on board), test across the HEAT and NEUTRAL terminals for 120vac.


IF 0vac at W and C, BUT 120vac at HEAT and NEU, the board is bad.


Could be underlying problems though that would require a total system check to rule out.


That requires special tools and experience.


Let me know what you read at above tests.



Thanks,
Robert