87 5000SQ Heater Fan Has Almost Stopped Working...

[Robert Bailey <baileyr@direct.ca>]

The heater fan in my 87 5000SQ has almost stopped working. I say almost 
because it appears if I put it "Defrost High", it will sometimes start 
running. Not always, though. I've had a quick look in the Bentleys, and 
it says on page 87.118 that if I "bridge cavities 1 and 3" on the blower 
control unit, the fan should run. I suspect that they mean bridge it with 
the plug inserted into blower control unit (ie. grounding that side of 
the blower). 

Is the fan the most probable cause of this problem? Or is something else? 
How hard (and how expensive) will it be for me to replace the fan if that 
is the problem? 

Any help will be appreciated as it's getting colder and frosty here...

Thanks,
Rob