mobilehomerepair.com

I have a coleman 3400-820 that the heating element is not turning off. anybody know where to start on this?

Thanks in advance

Jeremy

Hi Jeremy,

Look at left end of each element coil for a spade terminal on a white ceramic insulator.


Take a volt meter and place one lead on the terminal and the other on an unpainted metal screw.


Test for 120vac.


Do this with thermostat turned OFF and furnace coils still energized as you stated.


IF you do read 120vac on one or more coils, then remove cover of thermostat and test for 24vac across RH and W.


IF you read 0vac across RH and W, the t-stat is bad.

IF you read 24vac across RH and W, the sequencer is bad.


IF you read 0vac at each element coil, remove the blower assembly (screws at bottom flange on each side and sometimes along front), disconnect wiring and slide out.

Look down inside at coils and see if one has broken or fallen touching sides or frame or each other.


Thanks,
Robert

Robert,
Thanks for your reply. Just to be clear the t-stat is the wall mounted t-stat correct? There isn't one inside the furnace? I did test the limit switches just because I was there. they all tested good in a cold state. ( didn't heat to test if they worked or not).
Again thanks for your response.

Jeremy

Hi Jeremy,

Yes, wall thermostat (t-stat).


Thanks,
Robert

Robert,
Per your instructions I did some testing and everything tested correctly. I also noticed that when I turned the main breaker on the heating element stayed off as it should have. I made no changes at all and it all works now. Could this be caused by a weak battery in a thermostat?

Thanks again for all the help.

Jeremy

Hi Jeremy,

IF you tested as stated with furnace not turning off at that time, it would lead to the problem.


Need to know what each and every test result is/was.



Thanks,
Robert

This furnace is working fine now. I didn't do anything. I didn't even take the fan out to look at the heating elements. I tested the limit switches ( cold ) they tested fine and tested the voltage to the elements and got 0 vac. The elements just started to turn off when they were supposed to. Can't diagnose something that is working correctly. I guess I will just keep an eye on it and see if it does it again, then I can finish testing.

Again thanks for all of your help.

Hi,

Get out the volt meter and it'll skeer them furnaces every time,LOL. You're right, can't test or repair what is not broken at the time.


Holler when she hiccups again.



Thanks,
Robert

We she is acting up again. Maybe this time I can fix it. This time is different. now with the t-stat off the heating element is turning on for about 5 to 10 seconds and then turning off for 15 to 20 seconds then turning back on. When the t-stat is on she seems to operate normally when actually running. When the t-stat kicks off then the heating element continues to cycle.
Any Ideas? ( also the heating element turning on and off is accompanied by a relay click from within the furnace itself, not the t-stat)

what sequencer do I need the numbers on the one i have are 15sh22 309576
H1-110 c1-110

Thanks for your help.