Fresh air heater motor

[cstudep]

Anyone know the best way to test a blower motor on a fresh air style heater box to see if it is functional?

It is from a 1968 and I have it stripped down to it's various parts to repaint it, but I have no idea if it functions. Having a hard time following the wiring diagram I have as the wire coming off the switch is not labeled and it just seems to disappear into a mess of other wires so I am not 100% sure where it actually ends up going.

[BruceK]

Can you just use a car battery and test it on the bench? Aren't there two wires coming out of the motor housing?  If you connect it wrong it should just spin the wrong way - no damage. It's just a simple electric motor.

[MPlayle]

As Bruce says, there should be two wires from the motor.  I believe one was green and the other black.  The black would be ground (-) and the green/yellow power (+).

The wiring diagrams in my manual indicate a light Green with orange trace being power to the switch and the green with yellow trace being power from the switch to the motor.

It is also possible the motor grounds back through the housing and its mount to the body.  In that case the black wire may not be as obvious as it will likely be inside the heater housing.

[MiniDave]

The black wire grounds outside the heater box, I usually attach it to the stud at the bulkhead that the back of the heater box mounts to.

The motors themselves rarely fail as they don't get used all that much, but I've seen mice and mud-daubers build nests in them that can cause them not to run, so if it doesn't blow it's worth taking the assembly out and checking the fan and  motor for obstructions.

[cstudep]

Thanks for the info, this is how I assumed it worked but I could not get it to run so I wasn't sure if I was missing something and did not want to break anything. I have it pulled apart completely now. there is a Green wire with yellow trace as mentioned that runs from the switch to the outside of the unit. The other side of the switch is a black wire that then connects to one of the 2 white wires on the motor, the other white wire connected to a black wire in the harness near the steering column. All this color changing of wires doesn't help LOL

I just went out and completely disconnected the motor, bypassing the switch and got it to spin. I think there is an issue with the switch even through I was getting continuity through it when testing it. Guess I will just try to clean those contacts up, must not be a good connection there.

[MiniDave]

White wire connecting to a black one is not right - unless you're saying one of the leads directly off the motor is white and connected to the black wire - going to ground. The other would connect to the green wire or green yellow wire coming out of the switch. What you should have is a green wire going to one side of the switch and a green/yellow wire going to the motor, the other motor wire should be black or hooked to the black wire that goes to ground. There should be no black wires going to the switch.

[cstudep]

Yeah I think that is what was confusing me, someone must have changed the wire that runs from switch to one leg of the motor, although it does have a factory looking connector on the end of the black wire so who knows. It definitely does not look like your typical "after market" wiring connector and it is definitely black and not green. It does have the green with yellow trace coming out of the other side of the switch which would have connected to power. The other leg (white wire) of the motor also ran to a black wire under the dash into the harness connection at the column (this was the actual ground connection).

Perhaps when I put it back together I should swap that wire to green.