Brake lamp failure and its sad cousin, park lock out fails and locks up the 3/4 speed A/T shifter lever, in PARK    

If the brakes don't come on , the automatic transmission cars will not ever shift out  of park (unless the bypass switch is activated , <covered in the operators guide)
Same with cruise option, (auto cancel cruise fails, dangerous that be....)
So what to do,  ?
A: re calibrate it.?
B: replace it.?
Where is it.? Well it is here below.   This photo is upside down,  The master cylinder mount  rear, is that large hole at the bottom below, but this photo is clear.
Clear to see the switch mount, is threaded with a welded on nut, and clear to see the wires must  come off to calibrate it. (wired connector wires not shown)

That bottom lever is the clutch cable lever.

Next is the factory weak instructions. GM Chapter 5,  but sadly no photo of method or what a cushion might be.
Clock wise screws in the switch,  the par B is a Cushion newer years have no part 508 , only a welded base, there but the adjustment is same.

Next is my cheat sheet.

The switch rod in switch actual is spring loaded, if not its bad switch, and when brake pedal is up, the switch rod is compressed to 1mm length, that is SPEC.
1mm is the thickness of a match book cover!  use that, and is more than  accurate enough.

Cases in point.:
If the switch is loose then it's not calibrated, same with loose jam nut, same if nut is missing. (mine had  missing nut)
If the wires are hacked or cut or damage, dah? (soldering and heat shrink time!)
If the terminals are all rusty (green) , due to driving with broken windshield for 1 year?  then they need to be cleaned or replaced. (new terminals, as needed)
The switch closes to make brakes glow, after moving brake pedal a short  distance downward.
If the brakes do not glow the horn/brake fuse can be blown, or this switch bad or mal-adjusted. per above.
If the gap is too large the brake lamps glow all the time, key on.
If you depress the brake pedal and there is 12vdc on one pint and 0v the the other , then the switch is bad)   keep an eye on the fuse, if it blows, the brake lamps are shorted. (the wires or the bulbs can short)
If the switch fails Cruise option fails too.
The fuse  can be bad, some are RUSTY others have tiny unseen cracks inside, so replace it at 50cents.
The fuse is marked, STOP HORN
as seen here. 91-95'.

or all fuses  here, for other years.

If the fuse blows, or is loose (bad) the A/T transmission will  not shift out of park. (check that the rear lamps glow first!!!)


rev 1    9-1-2015