[Shotimes] Blower Speed Controller (BSC) Preventative Maintenance

[Carl Prochilo]

About a month ago I found out that my BSC was starting to fail.  With the
help of some friends, I located a used module, service information, and an
actual live view of the blower assembly removed from a SHO.  BTW, you only
have a BSC if your car is equipped with an EATC, but this is probably the
majority of SHOs out there.

Yesterday the BSC failed completely and I took to doing the repair, which
needs to be done from both inside the glovebox by pinching the stop tabs
(to remove the electrical connector and hose, and underneath the glovebox
(to remove the two retaining screws).  A 1/4" ratchet with a long
extension is useful.  The screws have an 8mm head.

The BSC is the kind of part that has some complexity to it, but to which
you don't give a second thought about.  In other words, it's like a light
switch in that when you turn it on, you just know and expect it to work. 
The module itself operates using a relay mounted on a printed circuit card
on one side, and a heat sink on the other side.  The heatsink probably
isn't the best design the engineers could have thought of, but it does
offer the added characteristic of providing structural integrity to the
relay PC board assembly.  The problem with the heat sink is that it is
prone to catching debris that flows through the blower since the SHO
didn't have an air panel filter (my 91 Alfa 164 and 2000 Lincoln LS both
had a panel filter).  What I believe happens is that once the fins get
clogged, the added heat to the relay accelerates the wear mechanism.

The preventative maintenance aspect here is, that even though your BSC
might be working fine, it is prudent to pull the part out and clean it at
least once.  I recommend compressed air and a stiff thin wire to get
stubborn debris out, keeping in mind that the aluminum fins are somewhat
fragile.
-- 
Cheers,
Carl Prochilo
1992 Ultra Red Crimson