HELP! Electric furnace won't stop running!

knchat

My furnace stops heating only if turned off at the breaker. I replaced the simple two-wire thermostat. The furnace still goes full blast regardless of thermostat setting. The fan switch doesn't make any difference. This old Coleman electric furnace needs fixing before freezing weather!

mickeyco

Be sure to turn off the electric before working inside the unit. This isn't that uncommon on Coleman electric furnaces, most likely it's the sequencer, you can completely disconnect the thermostat and if it's still on it's a pretty good indicator that it's the sequencer. The sequencer is a relay (switch) that controls the heating element(s), they get stuck on and then the high heat limit won't turn them off even if the fan isn't running.

I would replace the sequencer, fan switch and limit switch (high heat), at the same time, they should all cost around a $100 more or less. I get the parts at a local appliance center but I'm sure you can find them on-line somewhere or a heating supplier. The reason for replacing all at the same time is that when the sequencer goes out and the heat is stuck on, if the fan is not on the other switches (fan & limit) can be affected by overheating plus you'll eliminate a potential future problem.

Picture of what the sequencer looks like:

surfingusa

I had the same problem with my Coleman Presidential 2 electric furnace in my mobile home (1980).

I tried checking the two sequencers by placing a continuity tester across the terminals and then energizing the coil with a 24 volt supply, unfortunately I could not get them to work.

I did notice that two of the female quick disconnect terminal ends were very weak and were not making good contact on the sequencer posts, so I replaced those terminals and now my furnace is working properly again.

This is really not a job for a person with limited electrical troubleshooting experience. If you do attempt this yourself, I recommend that you draw a diagram of the components and use wire markers to identify each wire before you remove them.

Hates my roof

check the fuses too. but more likely its what mickeyco said. I've had this same problem on my GE electric furnace.