Brake Lights

[gskcommando]

Hey Guys,

Hope your all having great Commando outing this holiday!! And many thanks to all the vets out there for keeping our country free so we can enjoy our Commandos in our own way!!!!!!!!


Does any one understand how the brake lights work? That is, when you hit the brake pedal, what trips, switches or activates to complete the circuit that lights the brake light element in the tail light bulb?????


Thanks,
Gary

[Miket]

Gary,


Look under you master cylinder. There is a switch there that operates off the brake fluid when you depress the pedal. This sends volatge through the wire up to the turn signal switch then back to your brake light in the rear.

[gskcommando]

Curious. Thanks you for your help.

That is exactly what I found when I traced the wires. The wire going into the cylinder switch was hot, but the other wire, which goes to the tail lights, had no voltage.

So what are the possible problems?

1. Bad switch.
2. ???????????

[clffhnger]

To check the switch, have someone push hard on the brakes and you should get 12v on each wire. Then if you don't, take a piece of wire and short the two terminals on the (switch) plug. If the lights light up, the switch is bad. If you short it across and have 12v there, and no lights, you will need to keep tracing it.

[gskcommando]

OK, turns out that the brake lights and switch have probably worked all along. When I was testing the brake lights I was just forcing the brake pedal down with the club. If I pump the brakes a couple of times and then wedge the pedal down with the club the brake lights go on.

Sooo, the question then becomes, why do I have to pump the brakes?

Could it be there is air in the lines and bleeding is required?

Master cyclindar hosed??

Thanks for any help.

Gary

[clffhnger]

Sounds like air to me, or maybe the switch is going bad.
How do the brakes work? Do you have to pump them to make them work properly?
Napa sells a cheap master brake bleeder, you just take off your lines from the cylinder install this fitting with a hose that goes back into the resevoir, and start pumping slowly. I was really surprised to see how much air was trapped in my master, it took over 50 pumps to get all of it out.
Also an easy way to bleed the wheel cylinders is to get speedy bleeders also available at auto parts stores. You can bleed the brakes by yourself this way.

[gskcommando]

Mmmm........ The first stomp of the pedal pushes it down pretty far but the brakes work. The second stomp has the brakes work with the pedal down probably half as far.

I had to replace the axle last winter so the one line was open for quite a while (weeks). I thought I bled em all good but I am a born again mechanic (been 30 years since I turned a wrench) so who knows. Never heard of bleeding just the master.

Next time I get to work on the Jeepster I'll try bleeding again as you suggested.

Thanks,
Gary

[clffhnger]

All stomps should result in the same level on the pedal. You got air somewhere.
Masters usually don't have to be bled, unless the system has been drained (or empty) or it's a replacement master that you are installing. If yours didn't drain all out, then probably just need to bleed it at the rear wheels.