Coleman DGAT075bdd fan kicking on and off WO call from therm

[bbivens]

I have fought this problem for about 3 months now. I have a coleman DGAT075Bdd with air conditioning. The problem is that the blower fan will kick on and off without a call from the thermostat. I have even unhooked the thermostat and it still kicks the fan on and off. This usually happens after the thermostat cools the house in the early afternoon and has to run for 3 to four hours straight. I have to turn the power off to the furnace to get it to kick the blower off and sometimes if I turn the power back on it still kicks the blower on and off without call from the thermostat. These are the parts I have replaced. Control board 3 times, upper and lower limit switches and the thermostat. The last thing I have tried was a different control board the coleman 7990-320p instead of the 7990-319p. Any help would be appreciated.

Thanks

[DaleM]

One thing you could try is to run another thermostat eliminating all the current tstat wiring. Nothing special just drape it over a hallway door for a few days to see if that "fixes" the problem. Sounds like maybe a screw or nail is through the wire and something, heat maybe, causes it to expand and make connection.