Trane System Blower Motor

I’m having issues with a blower motor at my own house. I noticed a slight burning smell almost like a curling iron that has been left on if anyone is familiar with that smell. So I popped open the Air Handler access panel and noticed the motor seemed to be running slower than usual. I went ahead and replaced the run capacitor, however, that didn’t help even though the other one was slightly under tolerance.

So I pulled the 1/6 HP blower motor out. It is a 3 spd single phase, 1060 RPM, 230V. There was one red wire coming to the B terminal on the motor, which I have to believe is the power source. The motor was rated at 1.15 AMPS and when I put a clampon meter across the line I was getting that. It is 14 years old. It only has 1 yellow wire coming from it and 1 black wire. Then there is the ground that was screwed to one of the mounting bolts. I checked the resistance across all the terminals and this is what I found:

Yel to Blk = 88.3 ohms

Blk to Term A = 52.5 ohms
Blk to Term B = 37.9 ohms
Blk to Term C = 33.0 ohms

Yel to Term A = 74.7 ohms
Yel to Term B = 60.1 ohms
Yel to Term C = 55.2 ohms

A to B = 14.6
B to C = 4.9
C to A = 19.4

Problem is I’m not totally certain on what these measurements mean, other than the sum of the terminals A to B and B to C equal the measurment between the terminals C to A.

I just need to know if this is a bad motor because of the smell that we were smelling from the vents directly below where the Air Handler sits in the attic. Can someone please explain how much of this is relevant and what it should or should not read. The only examples I could find on line had a lot more wires coming from the motor, whereas mine only had the Yellow and Black. Any assistance would be greatly appreciated.


Steve :frowning:

I am short on time almost out the door but if you are talking indoor blower motor ya better check the voltage they are 120 volts the out door motor is 240 volts 14 years old its time to change it out your ohm just indicate conuinity no open windings

There was a second black wire coming to the run capacitor where the motor’s yellow and black wires were connected. I didn’t check the voltage across the red and black wires coming in, but I thought that would be two 110 V lines for supply. This is the blower motor for the Air Handler.

Lets just forget about the capacitor thing…

We need amperage readings not Ohms. Every motor is different and we have no clue what the stator resistance should be. We can play with Ohms Law but that still doesn’t tell us anything because we don’t know the true voltage or the power factor involved.

Motor nameplate will list RLA in Amps. Need to know this.

I would guess that you have melted some motor windings (which will change your amperage draw) and the motor magnetic field has changed causing it to run slower.

Get the name plate information the voltage, and the amp draw (with the blower compartment closed).

This happened to our old Trane unit. The blower motor is failing and shortly, will stop altogether.
In order to change the motor, you have to take the “cage” out, disconnect the fan from the shaft, then unplug everything and unscrew it all.

After finding the replacement motor, put it all back together and make sure you don’t bend the fan and that you get it on the shaft properly.

When we had ours replaced, the guy didn’t put the blade back on properly and the whole unit vibrated like crazy. I took it apart, straightened out the fan, sort of like truing a bicycle wheel, and put it back together.

It worked fine for the remainder of the time we had the system.