OT - Oil Furnace Troubleshooting

Trane Oil fired furnace was here when we moved in ~13 years ago. It was relatively new at that time so I am guessing it is probably ~20 years old.

Have done normal maintenance type stuff (air and oil filters). Probably had a winter tune-up by a professional twice in the time we have been here ( not sure it was worth the money since they only checked combustion by visually looking at the flame).

This morning the burner starts and gets hot, but the circulation fan is not coming on. It has a control board in the return section next to the fan and another high limit control (I think). Hoping some of the HVAC service types can give me some troubleshooting advice as to where to look. Right now I am thinking it's either the circulation fan motor or a control issue (what else is there), but haven't even opened it up yet to put any meter leads on it to try to follow power around. Any advice I can get to shorten the troubleshooting process. Given that it is a holiday weekend and relatively warm for this time of year I can probably get through the weekend. Local supply house is closed so any fix needs to wait until Monday anyway.

Thanks in advance,

Kirk

This is strictly a guess but I would clean the plenum. It may be sooted up and the sensor is not detecting clean air flow. I'm not real familiar with an oil furnace but I have cleaned my mother's a few times. It requires a good cleaning every fall.

Can you get to the fan and see if it spins freely when flicked with a finger ? If it is 'stuck', the bearings are dry. 'maybe' saveable with lubricating. I had a'similar' problem 3 weeks ago, Our washing machine stopped !! just hummed. I found that the motor would not spin even with belt off. Removed the motor and worked a very thin lube in to the bearings, could move the shaft back & forth just a little. But more and more, as I worked with it. Then added good oil, soon it was rotating fine and has completed many loads of laundry since then.

Kirk I am no expert but just like the high limit switch that shuts it down when over heating there is a chamber switch that calls for the blower to kick on when it gets to a certain temp in the chamber. Just about has to be one of three things. That switch in not closing, your control board is not functioning or the blower motor is out. Won,t take you long to trace those three things down.

Also if it has a soot problem it may be the draft is out of adjustment. Maybe someone who is more knowledgeable with reply.

I would start with the motor and capacitor. If they test good a jumper across the limit switches(one at a time) will tell you if one is faulty. Control board may have a fuse or reset so check that also.

Kirk, Do you have a fan limit like this? You can make motor turn on by carefully moving the limit settings. Some controls have a button sticking out that you can push in to make blower motor run. Have you checked the fan for movement? Just rotate belt like others have suggested.

Your thermostat on the wall should have a switch that turns on the fan manually. See if your fan runs, if not probably a bad fan motor. If it runs its probably the switch that kicks in the fan when the furnace gets hot. If the fan runs you can turn it on and let it run continuously, at least you will have heat.

to add to other comments. If the blower turns freely cut the wires and wire on a pigtail and plug it in If thew fan runs it's in the control circuit if it doesn't it's the fan motor. you could just let the fan run continuously until you can get the controls repaired