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MARamirez · Jan 23, 2007, 08:29 AM

I've got a Lennox G12 series furnace and the blower seems to have stopped working. I read a few posts and saw a reply mention giving the fan a little push start while the burners kicked on. I did this and the blower started up. I can hear the "current" feeding the motor but it seems to be having trouble kicking on. The user manual has "lubrication" instructions. Is it possible that the motor/fan just needs cleaning and lubricating? Or is this a definite capacitor problem or something else? I doubt the furnace has ever been cleaned/lubricated. I'm guessing it came with the house and it was built in 86.

esquire1 · Jan 23, 2007, 08:48 AM

Could be either. However I'll bet you going to be replacing the blower motor as well. When you replace motor may sure you replace with a new capacitor as well with the rating the motor calls for.

labman · Jan 23, 2007, 08:49 AM

Cleaning and lubing the motor can't hurt especially if it seems to have some drag or roughness as you turn the motor by hand. A little, smooth resistance is normal in a motor.

You can also make a rough check on the capacitor with any ohmmeter. Short the capacitor and disconnect the leads noting where they go if more than 2. Then connect the leads of the ohmmeter to a pair of terminals. It should show a fairly high value and climb to the top of the scale. If it initially shows open or doesn't climb to open, it is bad.

MARamirez · Jan 23, 2007, 12:48 PM

Thanks, I will attempt checking the capacitor when I get home. Do you know where the capacitor might be? I've attached an image of the type of furnace I have. I've seen something like a capacitor in the make up box... but I've been told it might be close or on the motor itself.

labman · Jan 23, 2007, 01:10 PM

The furnace you show is a little older model. Chances are the capacitor is in a bracket in the blower housing. Start at the motor. Some of its wires will go to the fan control center. At least 2 of them will go to the capacitor. The capacitors are usually a metal can, round or flat with rounded ends.

MARamirez · Jan 23, 2007, 08:03 PM

So here are a couple of picures of the furnace, the wiring panel (i.e. make-up box) and my attempt to capture the wires coming from the motor. The wires coming from the motor go straight into the wiring panel. The only other wires (green) are grounds. I don't know where the capacitor would be. Any ideas? I will call the Lennox help line tomorrow and see if they can help. I will post what I find out tomorrow. Thanks for your ideas and thoughts.

labman · Jan 23, 2007, 08:26 PM

Maybe the thing in the center of the third picture down, but I doubt it.

rickdb1 · Jan 24, 2007, 08:01 AM

Reach back up under that silver panel. It will be bolted to the blower housing...

MARamirez · Jan 24, 2007, 10:06 AM

I will check again this evening but I believe there isn't anything at all attached to the housing. I'll post my findings. Is it possible there isn't one? I am going to replace the part in the picture to see if that works. If it doesn't I will pull the motor and go have it checked.

rickdb1 · Jan 24, 2007, 12:10 PM

That is not the capacitor. That is the transformer in the second pic... The capacitor is where I said it should be unless someone moved it to a different location (Unlikely)..

This is a capacitor:

NorthernHeat · Jan 24, 2007, 02:32 PM

Follow the brown wire from the motor to it.

MARamirez · Jan 25, 2007, 10:07 AM

Well, my eyes weren't fooling me. The brown wire goes to nothing. I will pull the motor out and clean it then go get it checked.

labman · Jan 25, 2007, 10:47 AM

Wait, you may be getting close. Try looking around the end of the brown wire. Is it broken or does it have a terminal on it that would have fit on the terminals in the picture Rick posted? It sounds to me like the problem is the brown wire came disconnected. All you have to do figure out where it went.

Yes there are motors that don't use a capacitor, but that disconnected brown wire strongly suggests yours isn't the only furnace blower without one.

The thing with yellow and green wires coming of it is your control transformer. Notice that other thing looks nothing like Rick's picture. If it is a weird capacitor, it should have something on it like the 5uF in the picture, plus a terminal the brown wire would fit on.

MARamirez · Jan 25, 2007, 12:46 PM

No, the brown wire doesn't have a connector on it but it does have electrical tape. You can actually see it in the red circle. Come to think of it... there is one wire coming from that "thing" (switch/capacitor?) that wasn't connected to anything which I thought was odd. You can't see it (purpled circle) but the yellow wire coming from the bottom left connector was just hanging. Do you think it should be connected to the brown wire?

rickdb1 · Jan 25, 2007, 12:58 PM

Are there or are there not 2 brown wires coming from the blower motor? And are they for sure hooked to the motor? If yes to both, then you need to get a capacitor on there (5 MFD). If not, then someone may have installed an Induction start/Induction run motor. Not good...

NorthernHeat · Jan 25, 2007, 02:52 PM

Typically the red wire is for low speed, blue is med/low, yellow is medium/high, black is high, white is common-neutral and the brown wire(s) go to the capacitor. So If it is a 3 speed motor one speed will be unused, if it is a four speed motor 2 wires won't be used. I'm guessing that the yellow wire is just an unused speed and should remain disconnected.

MARamirez · Jan 25, 2007, 07:02 PM

OK, got the motor out. It has a red,black,white & brown wires + 2 green ground wires. The brown goes nowhere and the white goes to another ground (eventually) on the wiring panel. No capacitor in sight. The model of the motor is: GE, model# 5KSP29KK1892-S,PH 1,115V,60 Hz,1050rpm,7.60 Amps,1/5HP. So do I need a capacitor? Do I connnect the brown and white wires to it? 5 MicroFarads as suggested?

NorthernHeat · Jan 26, 2007, 03:19 PM

It is very unusual to have a split phase motor with a brown lead that is not a capacitor run motor, but it sounds like you have one. In going to say you need a new motor. It is not a capacitor run motor. It looks like the motor mount brackets are spot welded to the body, not just any motor will do. When you see the price of that motor from a Lennox dealer you may want a new furnace.

rickdb1 · Jan 26, 2007, 03:28 PM

When you see the price of that motor from a Lennox dealer you may want a new furnace.

Amen...

esquire1 · Jan 27, 2007, 08:14 AM

I would just get an aftermarket, split phase motor (and mounting ring) a capacitor rated for that motor and be done with it. You could do all this for less than $100.00 and less than an hour of your time and enjoy the warmeth of your home.