Back up speedometer switch help for reverse light

[FrankRam]

Anyone have any experience with the Back up/ Reverse Switches that fit behind the speedometers? I just installed one on my '57 oval's 6 volt system and I have achieved 100% negative function thus far. The switch is a Hella NOS 71 /21 6 . One wire attaches to the ignition terminal (3rd from left facing the trunk) and the other runs to the light. I have the light grounded to the bracket bolt. The contacts are good. Tried 2 different bulbs. Tried reversing wires from the switch. The speedometer works so I know its on straight and the switch is not stripped. I assume on the light itself the ground wire is toward the outside and the hot wire attaches closest to the bulb. All new 16 gauge wire.
I am out of ideas. Anyone experience this? Thanks for hopefully some enlightenment.

[Sunroof53]

Ideally you need a volt meter to check the voltage at each stage .Check for voltage at the fuse board ,move to the live side of the switch .You could jack the car and get a friend to turn the wheel as though you are reversing .Check for voltage on the other side of the switch .if there is no voltage then the switch is faulty if there is move your tester to the lamp and check again.if you have voltage on both sides of the switch then double check your lamp and wiring.
Personally i would run a live to the lamp and see if it lights up first.especially if you dont have a meter.

[FrankRam]

That is an excellent idea to jack the car and spin while checking voltage. I'll find me a meter tomorrow and hope the switch is good. Awesome. Thanks.

[Nessy]

[passoa55]

[Suboval]

Most times the contacts inside are corroded and that can be easily fixed. Gently lift the Hella sticker. Under it is a screw that holds the switch together. Remove the screw to get to the contacts and clean them - a pencil eraser works fine. Put a dab of grease on the contacts/sliding portion to prevent corrossion and to keep everything sliding smoothly. Reassemble the switch. You can use an ohmmeter to test the switch.
If the center post (the male one that goes into the speedo is broken) - just replace it. The bar stock can be found at Lowe's/Home Depot. File the sides to get the correct fit into the speedo. Drill thru the female and remove the rest of the broken male end. Cut the bar stock to fit, but leave a little extra. Mix up some epoxy, and slide the bar stock in thru the female side and epoxy it into place.
The speedo hot lead is connected off of the fuse box. Just make sure it is connected to one that the ignition key turns on and off or you might find yourself with a dead battery if the you backup and park.
_________________
It all works on paper.

There's two things we learn from history:
1.) History repeats itself.
2.) We don't learn from history.

[FrankRam]

I haven't jacked up left front tire, spun backwards and checked for current yet, as I don't really want to use stock jack in channel. I need to go to a garage and use a real lifter. Dumb question - Can I take the screw out, under the sticker, and clean the contacts without removing the switch out from the speedometer? It was tough getting it in there as I was barely able to pull back the cable far enough and I dont want to break anything.

Thanks

First, do no harm.

[johnshenry]

[FrankRam]

I would need what kind of 'bit' for that manuever I wonder?

[johnshenry]

[Suboval]

[FrankRam]

Gotcha. Best to do it right. Thanks for the huge tip!

[FrankRam]

[Suboval]

[Suboval]

Take a look here: http://www.thesamba.com/vw/forum/album_search.php?...t_dir=DESC
_________________
It all works on paper.

There's two things we learn from history:
1.) History repeats itself.
2.) We don't learn from history.

[Zwitterkafer]

I remember having a problem with one of these switches....the car would roll backwards a fair distance (too far!) before it would switch on the backup light. Cleaning the internal contacts didn't fix it for me; instead I had to make a finicky tension adjustment by bending the sliding metal ring that has the two contacts on its ends. This decreased it's diameter slightly and gave it a better grip after re-installation. It's hard to describe, but when the ring is too loose, it's like a slipping clutch, and there may not be enough force to positively close the contacts, or to at least close them promptly and keep them closed. If it is working properly, it shouldn't take several revolutions to close the switch.

IMO, the little accessory plunger switch (on a bracket placed near the shift rod coupling under the back seat) was a better design.
_________________
"Criticism comes easier than Craftsmanship"
- Zeuxius, 400 BC

[FrankRam]

I am so stoked thanks to you guys! 100% function as of now. The old SWF back-up light illuminates the whole garage at night. Turns out, the best fuse to hook up to was the 2nd from the left when facing from front of car, not the 3rd (of 4) as indicated from the speedo-switch instructions. Basically, it's any terminal that has power when ignition is turned on. I know that's sooo basic for most everyone, but when your a newbie like me, it's a revelation. A simple circuit-tester from Ace Hardware for $3.99 led me to this discovery. I'll try to do a picture in the next coupla daze. Kowabunga and "eep opp ork ah ah".

[FrankRam]

One further note: With ignition on, both sides of the reverse switch tested hot without spinning the tire backwards. I believe this occurred because the car was last backed into place.

[60ragtop]

[FrankRam]

All done ...