Furnace Blower not turning on

[wshenefelt]

I have a mobile home that has a DUO-THERM model no. 714080-001. The furnace blower doesn't come on. I turn the thermostat up and I can tell that the draft motor starts up and runs for a long time (more than 15 minutes) but the blower motor never comes on to heat the mobile home. I can tell that the pilot light is lit before I turn up the thermostat. After the 15 minutes I turned everthing off and I am looking for a solution. Any information would be helpful. I am not very educated when it comes to furnaces. I know the basic operations but I don't know how the complete system works.

[Robert]

Hi,

Does the burner ever ignite ? Will be back on later tonight.


Thanks,
Robert

[wshenefelt]

No, I do not think that the burner is igniting.

[Robert]

Hi,

You will need to know for sure whether burner is igniting.

If it is not, then you could have a problem with your flue piping/roof-jack, problem with the booster motor, problem with either the centrifugal switch or pressure switch depending on which it has.


We do not have any info on those older Duo-Therms or any parts for them except where a p/n is available on a part we carry for other furnaces.


Take care and best wishes,
Robert

[wshenefelt]

I checked and it is not igniting. I also might mention that when it was working last spring before I shut it off for the summer, it wasn't working normally like it used to. I could hear a pretty loud clicking and it seemed like the motor was having a hard time starting. Sometimes it would click on for a second, click off and then on and the motor started up. It was actually causing my digital thermostat to require more power to start the motor and would even cause the thermostat to reset as if the batteries had been removed and replaced. Maybe something might come to mind with this scenario. It did work when I turned it off for the summer, but now the draft motor is the only thing that comes on.
Thanks,
Wayne
Any and all information or advice would be greatly appreciated.

[Robert]

Hi Wayne,

Sounds like a faulty Fan & Limit Switch. That would cause the on-off-on symptom.

It could have opened and remained that way over summer and if open, your burner will not ignite.


The on-off-on could have caused a temporary problem with the 24vac low voltage side going to t-stat.


Locate it and see if it is open. best way is to jumper it if small 2 terminal style and see if it works ok then.


Turn power OFF, jumper, turn power ON and set t-stat.


Take care and best wishes,
Robert

[wshenefelt]

By Jumpering around the switches I was able to get the both the draft motor and the sqirl cage blower to work, but still no ignition of the burner. I was wandering if there is a way to see if the gas valve is opening up like it should or is there another switch that is operated by a detector that detects the pilot light. Maybe the furnace thinks the pilot light is out when in fact it is not? I don't know, I am just throwing it out there. I am just assuming that I have a pilot but no gas for the burner to fire up with. What controls that? I don't want to take up too much of your time but I think I am narrowing down to only a few possibilities. You have definitely helped.
Thanks again,
Wayne

[Robert]

Hi Wayne,

I could help more if I had some info on your furnace to see what components it has.

Do you have a wiring diagram ?


At the draft motor, are there any small pencil size tubes connected to it and going to burner area and one to a small round disc type switch with two wires ?

The 2 wires, if there is a pressure switch, one shows 24vac to ground, one shows 0vac to ground with call for heat.

Across them, you read 0vac IF it closed. 24vac IF it stayed open.



If so, could be the tubes are clogged, torn, switch defective.


If not, centrifugal switch in draft motor could be bad.


Draft motor Air Flue piping could be loose or clogged.


Gas Valve will show 24vac at terminals after about 2-3 minutes max time.


IF the GV shows the 24vac, then need to get the gas pressure checked.


That's about all w/o any knowledge on the unit you have.


Hope it has helped some.


Thanks for inquiring with us.



Take care and best wishes,
Robert