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Hi folks! Newbie here. Miller furnace model # CMF-80-AG serial #K-718177. Problem is that the blower will not run. I thought it might be the limit switch but the motor will not run even in "summer" mode. I don't see a reset switch or fuse any where on the furnace and the breakers at the panel are all good. Does anyone know where I can get a schematic for this furnace? I wanted to start tracing wires to see where the voltage is missing or stops. Any advice would be great! Thanks.

Jim

Hi,

Have you checked the Fan & Limit Combo Unit ?


We are trying to locate a wiring diagram.



Does the burner ignite ?



Have you checked to see if the blower motor is getting full voltage when it doesn't start ?




Thanks,
Robert

Hi guys! Well I haven't started to check wires just yet. I only have a couple hours each day to mess with this thing.

Anyway, The pilot is lit, the burner fires up, it comes up to temp and no blower, then the burner goes off.

I have a meter and would be able to check wires, but I was hoping to get a schematic before I started to try and narrow the search.

I think I chatted with Mark the other day about this and he gave me a part number for a switch. I went to check the part out and when I tried to get back to the chat he was gone. I lost the part number in the process.

Would the limit switch cause the blower not to function even in the "fan only" summer mode? It will not run even with the switch on.

I'm getting voltage to the transformer. Otherwise the burners would not fire. Right?

It's just hard for me to tell without a diagram.

Thanks for any help!

Hi,

We're still trying to locate a wiring diagram. The gas valve would have to have the 24vac from transformer to operate.


There is an aux. limit that may be in circuit, not sure.


Then there is the fan/limit combo that looks like this:


http://www.mobilehomerepair.com/media/i ... 626436.jpg





Thanks,
Robert

Well, I did some probing. Turns out that the motor is not getting voltage when put into summer mode or when the burners are on.

I looked for the fan/limit combo like you pictured. I don't see anything like that.

I'm going to probe more wires today to see where there is voltage and where it's gone.

The gas valve has voltage.
The pilot is staying lit.
Thermostat calls for heat.
The burners fire up.
It comes up to temp and then the click and no motor.
Burners go off and she sits idle.

Hi,

Where does click come from ? Have you been there since unit was new or did you move in with furnace already there ?


The pic I gave is the fan & limit combo for that furnace. It should be on left side of front facing, just below the blower housing.

Pictorial shows it laying on its side.


Someone may have removed and replaced with a non OEM part.


Find the click, it is a fan switch/relay and is most likely not closing and thus no voltage getting through to motor.


Thanks,
Robert

Could it be a capacitor?

It shouldn't have a run cap unless a newer motor has been installed with one.



Thanks,
Robert

It's ALIVE!!!! Thanks guys. It was indeed the limit switch. The click gave it away. Voltage going in none coming out. $65 later and I have heat! It would have cost me that just to have a guy knock on my door. You guys rule!

Thanks again.

Hi,


Was it this Aux. Limit Switch ? :


http://www.mobilehomerepair.com/media/i ... 626456.jpg



If so, are you saying it cost $65.00 ?




Thanks,
Robert