Coleman Furnace Model 7680B Series 856

[crusaderjsj]

Coleman Furnace Model 7680B Series 856----Sometimes the furnace seems to get stuck and it keeps going off and on, off and on--especially when it is running at a higher temperature like 70 degrees...at 65 degrees it doesn't seem to happen or doesn't happen as often. Last winter I replaced the fan/limit with part no. S1-7975-3281, but perhaps it is defective. If I turn the furnace off for awhile it will work okay again.

It has two limit switches #7680-379, one is on the front and one is by the blower, would these have anything to do with it--description says they turn off the gas at certain times.

Thanks for your help, Jardy

[hvac1000]

It could be closed off registers in parts of the home. They all need to be open in our types of homes.

Dirty air filter
Blocked cold air return
A thermostat that has the heat anticipator set incorrectly.
Could be a heat limit or other control that has fell out of calibration.
Dirty air conditioning coil will also block air flow and cause a problem.
A blower running at to slow a speed can also cause this lind of problem
A dirty blower wheen will also cause this kind of problem.

[bilbar25]

...It could be closed off registers in parts of the home. They all need to be open in our types of homes...

I just happened to catch this comment in passing by.

Are you saying that it isn't proper to close off a register in a room that perhaps gets a bit too warm?

Thanks....Bill

[Robert]

Yep, all registers should remain open at all times. The ducts are made of thin aluminum and smaller than conventional housing and the change in static pressure could cause problems.

That is just the main reason.



Thanks,
Robert