Furnace wont stay running

Xforce346

I live in a mobile home this winter has not been very nice. The furnace I have is a Coleman. I have been having nothing but troubles with it all winter. I replaced the Thermostat and still not working. I have taken out the thermocoupler and cleaned it so it was nice and shiny. I am at a loss to why it will not stay running. It runs maybe a 5 min cycle and then it turns off. Not enough to blow hot or warm. The pilot light stays lit. I just cant get it to run for longer. I know with the old thermostats that there was a cycle on them. I tried that before i replaced it and it still didnt work. I included some pictures to help. As you can see the pilot light is lit.

JUGHNE

Does the big blower fan run at all?

Xforce346

Yes the blow runs fine.

JUGHNE

If this is heating only, no AC, and IF there are only 2 wires at the thermostat, then you could just tie the 2 wires together temporarily to eliminate the t-stat as the problem.

Xforce346

https://youtu.be/uTweFi2oc7U

i uploaded a video. Its only running for about a min before it shuts off again. I tried the two wires it still did the same thing. I replaced the thermostat because it was mercury as well.

JUGHNE

Does the blower shut off before the fire? If you have a fan switch at the t-stat or inside the furnace and turn it "on" will the fan run continuously?

Xforce346

the fan switch is on. But the fan does not stay on continuously. There is a little fan button switch on the left side of the fan. I know I had to push that button in once in a while to get the fan to start but I haven't had to lately.

JUGHNE

Sequence of operation: with pilot light on.....t-stat calls for heat, main fire turns on......fire box warms up......thermo switch on fire box turns blower fan on..........all runs until t-stat is satisfied with room temp....main fire shuts off.......blower fan continues to run until fire box cools off.

It sounds like your blower motor is overheating and shutting itself off on high limit. When the air flow stops the fire box will get too hot and shut the main fire off. The button you are pushing may be the manual reset for the high limit temp of the firebox. Resetting that should not start the fan, rather it will allow the burner to cycle again.

Your fan motor should run non stop with the fan switch "on". If it stops after a few minutes it is probably hot as hell by now.

You most likely need a new fan motor or if lucky only a new motor capacitor. The whole thing comes out pretty easy and maybe a motor shop could check it out. But you can NOT continue to fire the furnace with the fan failing.....this will create a dangerous situation in a mobile home.

Also note that your water lines may be run along side the hot air duct under the floor and rely upon that heat to prevent freezing.
Frozen water in a trailer house a real pain.

Xforce346

i found that one of the temp switches I touch might have a bad wire or connection maybe I am testing it out and I will get back after.

hvacplumber7

Sounds like jughne might be rite. Looking at the side of the blower housing this unit doesn't appear to have been serviced in a long time. If you pull the blower to check it, it would be worth your while to clean the blower wheel, check the heat exchanger for cracks, and if you have ac, clean that cool as well. I see hundreds of these a year, and most that look like that have bad heat exchangers. May be worth calling a pro.