Can't figure out why my brake lights won't come on

[brittbolen]

I've spent all day trying to figure out why brake lights are out.

here is what I know:

1970 911E. No power brakes.

I have the mechanical switch that operates the light and is screwed into the pedal cluster.

I have current. Disconnecting the 2 wires from the switch and shorting them together gets me lights.

I have goot connectors because I cut off the old ones and put in new spade connectors.

The switch appears to work. When I hook it to my multimeter to the switch the switch appears to work, as in the circuit opens and closes. This continues to work when I install the switch on the pedals, though I think i have to press down too much to get the circuit to close.

When I hook everything back up, no lights. I do notices that the switch and connectors get a bit warm.

Is it possible my switch, when closed, has too much resistance? I'm loathe to just replace the switch seeing as it's $70!

Any ideas what else I should try?

thanks,

Britt

[Bill Verburg]

If the lights work when you manually close the switch be hand, that is showing you that the switch is correctly working, so then the switch needs to be shimmed closer to the pedal. The pedals in the older cars had a minimal amount of travel and need to be positioned just right.

[project 911]

There is a small threaded brass adjuster with a brass nut on my switch (1971) that adjusts when the switch actually makes contact. When I put new brake pads in, the pedal travel didn't go far enough to trip the brake switch. Try adjusting this until the lights come on (with the pedal pressed down a little).

[stlrj]

I had the same problem on my 74. I removed the switch from the pedal cluster, found the small brass adjustment screw, made a few turns ( can't remember which way), put it back on, fixed!!!

Cheers,

Joe

[brittbolen]

I think there were 2 problems.

1) bad wiring on the connectors to the switch. I pulled the old spade connectors off, put on new ones and crimped the hell out of 'em.

2) switch needed major adjustment. Removed the little brass nut, cranked the screw down, and voila brake likes right when you hit the pedal all the time.

thanks everyone!

Britt

[filou]

What's having me worry is the fact that the connectors and wires get warm when in use. It is kind of clear that you must have a short to ground. You said that you own a tester (ohmeter). Just make sure the circuit do not have a short (path) to ground when you reconnect everything. That will explain why, the components get warm and you can't get the lights to work. You see in electricity, the current ALWAYS choose the easiest path.
Put everything together but do not place pedal switch to his final place yet, and do a operating test by manually releasing the switch.
Then, does your brake lights come on ????
With meter on Voltmeter mode, check your juice delivery all the way to the switch.
A proper adjustment of the assembly needs to be right on.
If it is off, when you operate the brake pedal, you are pushing too far the switch to the piont where it makes contact to the body of car (ground) and you are creating a short which would explain the warmth felt at the switch and wires and the NO lights thing.
It is kind of a pain to work underneath there i have to admit.
Good luck, Filou.