Blowing fuse - Blower Motor

[Grnrvrs]

Now that it is starting to get cold out... I'm having a recurring problem with the 20amp fuse for the blower motor popping. This is driving me nuts.

Upon start up, the blower motor fuse pops.
Control lever set to off, it pops.
Control lever to low or high and it pops.

If I disconnect the multi-plug at the blower motor (power in and high/low ground out) and then reconnect, the blower will run on ACC power, I can start it, and it will run high/low/off. When I turn off the engine and restart, it pops.

Ideas?

 

[Grnrvrs]

~12.6v to the plug
continuity for low ground
continuity for high ground

 

[John Z]

May be a short in the resistor for the blower motor? From what I recall the OEM motor uses a switched ground meaning when the switch is off it's still getting power so if there is a short in the motor or resistor it's going to pop.

 

[Napalm00]

Maybe the blower motor is partially seized or something and the initial amperage is too high? Not sure if that would explain why it blows when it's not running though?.

Maybe take the grille off and see if the squirrel cage spins smoothly

 

[WreckITFrank]

I just did the VDO parts store upgrade. Cost about $80 these days and is worth the upgrade either way as the fan is likely stronger than the OEM new out-of-the-box. Took the time to put in rivnuts on the lower footwell, and replace the main flap foam as well. No coolant lines needed disconnecting, and I didn't take the fender off. Fixed my similar issue.

@javelinadave has a great write-up in the how-to section.

 

[Grnrvrs]

The old motor spins, but is stiffer than I would expect. The heater box is out and I'm working on the VDO swap.

Do the following resister readings make sense?
.6 ohms high
2.8 ohms low

Are there other electrical checks I should be doing?

 

[Grnrvrs]

Alright, pulled it apart, swapped in VDO PM 137. I swapped over the RHD squirrel cage. Duralast 246 was not available locally but S568 from O'Reilly Auto Parts is the same thing and available when I needed it. After putting it all back together, the fuse did not pop! The air flow was quite something, bordering on gale force. Hopefully, I'm done with heater mods. Thanks to all who helped.