123 Backup Light Switch Install

[rothgar]

Hi all,

Well, I've been lurking on the group long enough. It's time to start asking questions. Hopefully one day I'll be able to offer a few answers.

I have a 1979 300D. Can anyone offer a DIY on how to replace the Backup Light Switch? There doesn't seem to be much information on this.

Thanks!

-Eric

[Nicholas230e]

Hi Eric,

Is it a 4spd standard or automatic? I did my 4spd a while back so I could help you out.

Nick

[rothgar]

Hi Nicholas. It's an automatic.

Originally Posted by Nicholas230e

Hi Eric,

Is it a 4spd standard or automatic? I did my 4spd a while back so I could help you out.

Nick

[Tristar1959]

According to my Haynes, which describes adjustment - you may be able to adjust the actuator.

My Haynes says to raise car and place on jackstands, of course.
Place floor shifter in Neutral.
Remove control rod from shift lever (screwdriver lifts tab, allows clip off)
Loosen adjustment screw (about 2 o'clock, facing side of tranny)
Place a 0.16 rod aligned in the notch/hole in the housing and lever (about 4 o'clock); retighten screw, reattach control rod. [ If aligned without having detached everything, obviously not an adjustment problem...]

If you need to change it out, use your own sense of how it attaches - the shift lever clamps with the radial bolt holding it "around" the flat in the shaft.
Note and feel position of shifter shaft, in case you inadvertantly move it)

But before all that - have someone watch for lights as you move shift lever through positions Neutral and Park - to see if it may just be an adjustment.
Also if you have backups with power jumpered directly to them (bulb mechanisms easily accessible by undoing thumbscrews holding covers on, inside trunk - include checking bulbs in other known good positions)

How's the position and engagement/denial of your Park and Neutral start capability?

Stan

[Tomguy]

ADJUSTMENT
Reinstall the switch. Leave the adjustment screw slightly loose. With the transmission in reverse, and the ignition on (so the backup lights actually light), move the adjustment tab until the backup lights go on - a helper may come in handy if you don't have a garage door to see the light reflect off of. MAKE SURE to set the parking brake AND chock the wheels! Testing reverse instead of testing park ensures that you get all three (Park, Reverse, and Neutral) right the first time. To double check, tighten the adjustment screw, then get inside the car. Turn the ignition off and move it through all the gears. Then, put it back into reverse and turn the ignition on. The backup lights should light. If not, readjust the tab until they do. Retest. Then, once that is successful, make sure the engine cranks in Park AND Neutral.

This is my adjustment procedure for the 108, I would assume it's similar on almost any vehicle with an adjustable safety switch.