Heater Blower Motor Diagnosis?

[NathanR]

I fried the engine compartment heater blower motor yesterday in my 87 Carerra. It smoked up the cabin of my car. When I pulled it, it would not rotate freely. I assumed the bearings seized.

My neighbor and fellow pelican, Dru Martin, who had previously installed SSIs and heater backdate was gracious enough to let me try his old one blower motor, taken from his early 80s SC.

I was messing around with both blowers and measuring the resistance across the terminals. Dru's measured 5.4 ohms. Mine was infinity, must have melted completely.

Dru's blower fit perfectly. All I had to do was splice in the terminal block onto the blower leads. I plugged it in and it even worked. Then I reassembled everything and went for a test drive.

When I pulled the heater levers I heard the motor come on for a moment then nothing.

Drove home and 25A fuse in the engine compartment (position 2) is blown. Measured resistance across the motor again and now it's 0.5 ohms. Pulled everything back apart and tried even jumping the motor straight to the battery and it didn't work.

I suppose its possible the replacement motor failed by sheer coincidence. Could the rest of the system is destroying the motors? Is there something else I should check out? I'd hate to buy a $$$ new blower and immediately destroy it...

I should mention my right footwell blower is currently inop and disconnected.

Thanks in advance for your thoughts...

Nathan

[RDM]

Nathan,

What voltage are you getting at the fan wire?

Do you have a voltmeter in your car? Maybe a voltage regulator problem.

Info to the board: The fan I pprovided to Nathan was dismounted about a year ago and stored in my (dry, heated) workroom. Not sure how they degrade when not being used.

[john walker's workshop]

used ones are a pig in a poke. you can disassemble and see if the brushes are still good or if a wire broke, but if the bushings are egg shaped, it's over.

[faverymi]

I got mine rebuilt, rebushed , new bearings at the local alternator shop.

They also did the footwell ones. They were frozen.

I wanted to keep original. Very happy with the results.

Good for another 25 years!

[NathanR]

Dru,

I'm going to have to pick up some more 25 Amp fuses before I can measure the voltage at the plug, will do that in the next few days.

Do you know of a local alternator shop?

Cheers,

N/

[RDM]

Originally Posted by NathanR

Dru,

I'm going to have to pick up some more 25 Amp fuses before I can measure the voltage at the plug, will do that in the next few days.

Do you know of a local alternator shop?

Cheers,

N/

The voltage at the fuse (holder) should give a good indication of the voltage at the fan (assuming intact wires, which should be checkable).

John got his alternator and voltage regulator done by the Bosch shop just off Merkurstrasse, a block or two past Saturn on the same side of the street. I can go down there with you if you'd like.

[NathanR]

Dru,

That's a good point. I'll check it when I get a chance (out of time for today...)

I may try to find that shop on Friday. You're welcome to tag along if you have time.

Cheers,

N/

[jason2guy]

Heater Blower fix- cheeeeep

[NathanR]

Jason,

Thanks for posting. I think it's cool when people post solutions like that. If I have to buy a new motor, I'll look into it.

How did you find exactly the right sized motor?

Cheers
N/

[jason2guy]

i searched ebay for blower motor listed by price, lowest first. that one came up and it had some specs listed, shaft size, motor dimensions. for 15 bucks it was worth a shot. its working great by the way

[RDM]

Nathan,

Here's a picture of the simple heater backdate I was trying to describe to you. This solves the heater blower problem….

The picture would be less shocking in black and white, but what can you do? It makes it really obvious where the new part is, anyway!