Help with Coleman Presidential II furnace

[msufroggy]

Hello,
I have a Coleman Presidential II furnace that went out on me last March.
Here is what's going on:
When I turn the thermostat up, I can hear the furnace click on, and can hear the draft inducer motor (I'm assuming that's what the "humming" is), but the blower never starts up. It will just constantly "hum", until I turn the thermostat down.
The pilot stays lit. The blower will come on if I turn it to "manual" (although I don't get any heat this way-it just blows room temp air).
I haven't yet checked if the burners light. Would I be able to see them light through the pilot hole? From what I understand, the blower motor won't run until the burners flame up and the appropriate temp is reached in the furnace?

I am a single parent, and really am frustrated about this, as I don't want my child (or my pipes) to freeze this winter. I already blew out my stove ignitor trying to heat my house up last March!

I'm hoping it's an easy fix, or if you can help me troubleshoot further, I would really appreciate it!

Thanks in advance!

[Robert]

Hi,

What is complete furnace model number ? I will help if I can, but for most part, with this being a gas furnace and an ignition problem, it needs the attention of an HVAC Tech.

I know that can be tough on a single parent, but trying to DIY with no experience on a gas furnace could quickly prove fatal for yourself or child.


That is my number one concern, the safety of your child and yourself.


Most likely, the hum is the inducer motor trying to start, but not able to.


Take care and best wishes,
Robert

[msufroggy]

Hello, Robert. Thanks for the reply. Here is the model #:

Model: 7710-856

Serial: 068360305

It's a 95,000BTU input, 70,000BTU output.

I was not going to fix it myself, but I a relative in the heating and cooling busines (but I don't know if he does mobile home type furnaces).

Would the hum be the inducer motor running? Because when the furnace was working, I would hear that same hum for 30 seconds before the blower comes on, so I assume that the inducer motor is working, but something is not starting the furnace. Like I said, I haven't checked if the burners even light, but the pilot stays lit.

Thanks for all the help! Trust me, I would NOT try to do this myself! (even though I am somewhat mechanically inclined, but I do not like working with gas!)

Oh, I should also add that I do have central air that works with the furnace, but the air does not blow cold anymore, so I haven't run the air in a little over 2 years.

[Robert]

Hi,

It could be the booster (inducer) motor running or trying to run.

When your t-stat calls for heat, a signal (24vac) is sent to a booster relay which energizes and sends 120vac to booster motor.

When the booster motor reaches design speed, the centrifugal switch inside motor closes sending signal (24vac) to gas valve.


So, need to see if t-stat is calling and sending 24vac to booster relay ? If so, is the relay sending power to booster motor ?


If so, is booster motor running ?

If so, is 24vac being sent to gas valve ?


Humming could be a bad transformer also.


Take care and best wishes,
Robert

[msufroggy]

Thanks, Robert, for all of your advice! It is appreciated.

[Robert]

Hi,

You're very welcome, happy to help.



Take care and best wishes,
Robert