So, the 4 Dr sedan I just bought had an inoperable blower motor...last night did some diagnostics...blows hard when I jump 12V to the motor...ok

Next, I tested at the switch - power there

Next, I tested at the resistor (inside the heater box -PITA) - power to the respective leads at high or low switch positions

Resistor coils glow red - assumed it was bad - pulled a spare out of the parts car - low speed then worked for a little while, but then nothing.

First question: Are these supposed to glow red? I know they get hot as they're creating the resitance, but...

Second question: Anyone have a schematic for this - outside of the shop manual? There's a lead off the resistor that appears to go through the heater box door latch - not sure what this does?

Third question: How do I know if the resistor is good or bad? What goes 'bad' on them? Not sure what level of resistance I should be getting through the coils.

I supposed worst case I could just jump the terminals and just have "High" speed all the time.

If anyone has experience with one of these it would be helpful....it's getting cold here in RI!

 

If you have something out of one end of the resistor then it is OK...check that lead from the heater door (white wire)- to blower or defrost switch...resistors get hot that is why they are mounted inside the heater- to keep them cool. Check for continuity from the resistors to blower motor...try that.....cool in RI eh? present temp here is -26 C...

 

Yeah...I think it's definately the resistor - the one I yanked out of the parts car was likely bad. If I jump it (bypass it) the motor blows fine so it has to be that. Thanks for the input...problem now is finding a good one.

Anyone out there have an electrical engineering background? I must be able to buy Radio Shack resistors with an adequate capacity and solder them on to the original base, no?

For now, the heat blows and I can drive her.

And as for the -26C...could be worse....could be me!

 

Just for info: HEATER RESISTER GM Group# 8.852 Part# 3131533 is for ALL 1954-56
this may help you find one. Somebody has it on a shelf. I'll still be looking.
Here's a link for Part Numbers and list of Parts on hand from Collectors Auto Supply for your 1955:
http://www.collectorsautosupply.com/query.asp
They have your part listed and show no inventory, but they may be able to help finding one.
I found 2 new Resisters for my 63 Olds 88 on e-bay ( he even lived nearby)