Dying heater fan, '86 5K

[smitht@unb.ca (Tim Smith)]

The fan has been twittering slightly on high for a while, and has just quit
running on low.  This AM high was dead, but with cursing and by taking off
the access plate in the airbox I was able to push start it.  Has worked fine
on/off several times already, but where is it headed? Is total failure,
wiring meltdown imminent.  And.. has anyone drilled through the plastic
housing in the motor section to try and oil the bearings? Annual oiling
might save the teardown. Fan spun freely when pushed, which makes me suspect
brushes. 

Speaking of brushes I noticed the LCD panel for the radio flickers/dims at
idle but is steady at higher RPMS, alternator brushes going too?

  Final question, My 5000 turbo is labelled a CD, not CS or S. Cannot find
that listing most times I've asked for parts, anyone tell me what it means.
Like did the N fall off for CDN, eh?  Thanks, Tim