Dissected my throttle switch...'86 5KCSTQ

[Audial@aol.com]

Today I removed and opened the idle switch on my '86 5KCSTQ.  I did this
partly out of curiosity about how it looked inside, partly because I wanted
to know how difficult it was, and partly because I have had an episode of
high idle speed recently.  

Getting the switch off the throttle body is very simple.  Two 7mm bolts.
 Just remember to mark/paint the location of the switch before you remove it.
 Then disconnect the harness and firmly and evenly pull the switch off the
throttle body shaft.  Before I did this, it became clear that my switch was
out of adjustment and was at the outer reaches of sensing idle position.
 When I say this I mean that opening the throttle by hand, and then slowly
letting it close, failed to engage the idle switch.  If I let the throttle
"bang" closed, on the other hand, the switch would click.

Getting the switch opened was another matter.  There are four plastic tangs
that look as if prying them back will pop off the cover of the switch, but
this isn't so.  The upper cover is epoxied in place.  I scribed around the
centerline of the switch with an x-acto knife, making a complete
circumference around the switch until I had a well-defined, straight groove
(except for the tangs, obviously).

Then I very carefully inserted the edge of the knife into the groove and
pushed it underneath the plastic on the top side of the switch.  Soon it
began to break free.  By sliding the blade along carefully, you can "shuck"
the throttle switch open.  Take your time.

Here is a description of the inside of the switch:

The two positions (IDLE and WOT) are actuated by the central shaft driven by
the throttle plate.  On one side (idle) of the switch, the shaft actuates a
single-pole microswitch (mine is imprinted BURGESS - England).  This switch
and its associated contacts were <pristine> and worked just fine.

The WOT side of the switch is closed by a cam attached to the central shaft
that pushes two contacts together, a-la a breaker-point setup.  One terminal
of these contacts was very badly corroded...evidently the case was
inadequately sealed in this area.  However, I was still able to get reliable
meter readings, so I simply cleaned the solder joints up and got as much of
the corrosion out as I could.

Now: resealing the switch.  I am going to try scraping off the remnants of
the epoxy and first sealing the switch with Krazy Glue, and then adding a
fine bead of silicone around the entire circumference.  

It seems to me that what kills these switches is a breach somewhere in the
sealing of the case that lets moisture inside.  Alternatively, the IDLE side
microswitch might fail.  But the WOT side looks like it would last forever as
long as there is no corrosion.  

Best Wishes,
Alex