My intertherm furnace comes on but, sometimes it will shut off and sometimes it stays on until I have to turn the breakers off. What do you think is wrong? Thanks

Model #? Gas, fuel oil, or electric heat? When the unit "stays on", is it heating or just blowing cool air?

Model# E2EB012, electric, heating

Sounds like a possible sticking heat sequencer. Try good old KC13's trick and hit it with the plastic end of a screw driver when it is stuck and see if it shuts off. They usually look like this in the Coleman line and if it does shut off proving the sequencer as defective replace it after turning off all the power breakers to the furnace. Make sure to mark all the wires to the sequencer so you can reinstall them correctly.

I have replaced the sequencer and the relay but still have the same problemm

Then you better be checking the sequencer or relay for proper operation since these are the controls for the furnace. Just because you replaced the parts with new parts do not automatically mean they a good. The only other thing it could be woruld be a intermittent short in the thermostat wires OR a real reach is a defective thermostat.

Next time it does not shut off disconnect the W and RH wires off the terminal strip in the inside unit. That will remove the thermostat and thermostat wiring from the circuit. If it shuts off then the problem is in the thermostat wiring or thermostat.

I already thought about the tstat and disconnected W and RH wires but it did not shut off. I just went on line and ordered an original replacement sequencer to replace this "generic" one the local parts place had to offer! That should fix it. Thank you so much for your help and time! Kevin

Make sure you follow/check your furnaces wiring diagram when installing the new one.