Here is the schematic

Another view




This blower motor is old, possibly from 1994 - just trying to hold it together a little while longer. Started screeching intermittently.

I am now pretty well versed at removing the motor itself completely - I tried oiling the bearings - but can't figure out how to hook up the Century master fit pro universal replacement motor. There are a gazillion wires.

I guess the first thing I should try to figure out, do I have a 3 line circuit or a 4 line circuit? There are 3 wires from the furnace going to the motor, but I don't want to assume anything. It's a Trane XE 1000 heat pump. As far as I know, it uses the same speed for heating and cooling. I don't want to let the magic smoke out of this motor! Thanks for any help.

 

I would wire the new motor 4 wire. I would connect the two new brown motor wires to the cap and connect old black to the new motor common and connect old red to the speed you pick on the new motor.

 

I had a similar construction with same problem. Problem turned out to be the fins in the squirrel cage fan became loose causing the noise. Fins were held to the cage by friction only. Replacing the fan fixed the noise.

 

 

You are only using one speed. Red lands on the speed.
Red is one leg and black is the other.
Black hits one side of the capacitor then it goes to the motor.
The motor brown wire without a stripe hits the other post on the cap.

What number is red connected to on the motor?
What is the horsepower of the old motor?
What is the voltage of the old and the new motor?

 

It looks like red lands on medium speed...

 

You have a 3 line circuit. Cap off the brown wire with a white stripe.

 

Thanks so much for the replies! I'm starting to get an idea, but it's very nice to hear confirmation.

The old motor is a 1/2 hp 1075 RPM 220 volt unit, 3.3 amp, 60 hz single phase, 48 frame etc. The new motor is a Century masterfit pro. It is the same voltage - although it uses a white wire for the common.

The red 2 or speed wire is connected to terminal "B" on the old motor - I think I could just install a bullet connector to the new red wire (from the new motor) and connect it to the receptacle side of the existing wiring harness. To be clear, it is OK to connect the new Red wire to the old Red wire? or Terminal 2 would be better in terms of things like voltage drop. (if it will reach) I didn't dig around to look for the terminal block.

The sort of tan colored wire on the existing harness (labeled as blue on the schematic!) is in the terminal "A" connector on the old motor. That one, that wire can just go bye-bye? Cap it off, tape it up, remove it entirely? Terminal "C" on the old motor is unoccupied.

Blk/3 then, is common, and connects to one side of the start cap. The new motor white wire is the old motor black wire or common and connects to same. Correct? I understand this is more of a 120 volt convention, but it is a 220 volt motor according to both box and data plate on the new motor.

The new motor start winding wire is colored solid brown, and connects to the other side of the capacitor. It is yellow in the old picture and on the schematic. I'll tape off and roll the brown/white wire and roll it up out of the way.

I guess right now, the existing tan wire in the harness, listed as BL /1 on the schematic has me confuzzled. It isn't necessary? I'm sure my confuzzlent will not be diminished as I go through this. It's warming up to 39 tomorrow, so I can rest a little easier. The pressure has gone down.

I dropped the thermostat way down, so it wouldn't run very often, and cranked up a Mr. Heater. The motor started complaining loudly when trying to maintain 65-72F after some run time. It is intermittent, comes and goes, but I've seen this movie before. I tried to oil it properly with 20 wt. but it didn't seem to help at all. It is at least 20 years old, maybe closer to 30, so it's done well.

 

"It looks like red lands on medium speed..."

Yeah, the legend in the upper L/H says "B" is medium.

OK, now I have to think about this. (Always a sketchy thing) it then follows that I'd want to use the "medium" speed wire from the new motor?

In other words, the yellow wire. Connected to the red wire, or where the red wire currently now terminates?

 

This webpage sure crashes a lot on my smartphone. I can't reply to anything.

 

I would try medium high first. If it is too noisy then I would swap blue and yellow.
Looks like 10MFD is the cap for 1/2 horsepower.