Brake lights

Hi All,

I have a delema that doesn't make sense to me. I finished re-doing the wiring for the tailings I now have brinkers and running lights. I can't get my brake lights to work, I have 5.5v on one wire going to the master clyinder, if I "jumper" the other wire to my battery I have brake lights. But if I "jumper" the Hot brake wire to the other wire I get nothing. I'm at a loss as to what is the problem. My Jeep is a 57 6v system is the loss of .5 v causing my problem?

Thank you in advance.

Jon

 

"...is the loss of .5 v causing my problem?"

Not the voltage, but the amps. You may be able to get 'normal' voltage but possibly insufficient current, if there is a poor connection in the supply (such as a corroded connector).

See if the input voltage drops drastically when the pedal is pushed (or when you jump the switch). If so you need to find the fault which is creating the resistance. Your hot-wire-to-the-battery test would seem to indicate the hot feed to the switch is poor.

 

I got about 6months from a swich from Wallcks

 

Bad switch/good switch is another story. Like PeteL sez, you are loosing the required amperage from your power source, either from the battery terminal at the ignition switch or from the circuit breaker behind the light switch.

 

Thanks all

Makes sense I forgot about amp's I'll work on it tommorow.

Jon

 

"Bad switch/good switch is another story"

Agreed. Not likely the switch since he tried bypassing it and got the same result.

 

I will test the switch once I get the wiring figured out. The switch is newer so hopefully it works.

 

"The switch is newer so hopefully it works."

Usually the opposite, generally, in my experience! Newest item is the first one to suspect.

But we know your brakelights need a good hot wire first, no matter what.

 

I'm bettin you have a faulty turn signal switch...

 

"I'm bettin you have a faulty turn signal switch..."

It would seem not, since the lights work when he puts power to that side of the circuit.

 

Agreed. He has already tested the integrity of the circuit when he applied power direct from the battery to the "other" wire that turned on the stop lights. That means the circuit through the turn sig switch and all the way back to the lights was good. All that is left is the amp carring capability of the power wire going into the brake stop switch.

Scenario=If the jeep is wired as original, meaning stop switch power is coming off the circuit breaker and the brake stop switch has an internal short to ground, then it would trip the breaker leaving no power going to the brake switch.

 

Possible ground issue also.

 

The turn signal switch is the "brains" of the system. If you simply short the pressure switch on the master cylinder with a test wire or screwdriver the brake lights ( or some set of lights) should come on. If they don't then you have a wiring problem somewhere upstream -- most likely the turn signal switch. The brake lights should be powered from the headlight switch, so that they work without the ignition being on.

Don't rule out a simple wiring mis connection. I've seen a jeep wherein when one depresses the brake the front parking lights came on. That was a simple wiring problem --- swap two wires going to the turn signal and it was 'fixed'.

After 50 years or so of use the turn signal sometimes gets 'confused'. It is a relatively simple task to take the t/s apart and disassemble the innards of the switch. Some emery cloth on the switch contacts -- get 'em nice and shiny without taking too much material off of them and re-assemble. That will most always solve any and all problems with the switch. If you can get some di-electric grease you can lubricate the internal terminals of the switch, but ONLY with a di-electric grease, and ONLY with a tiny bit of grease.

Jeep wiring is awful simple -- especially as compared to new autos where a problem in a wiring harness is almost a total loss of the vehicle.

 

"If they don't then you have a wiring problem somewhere upstream -- most likely the turn signal switch. "

Except, the signal switch is what I would call "downstream." On that basis he has apparently proven the fault is on the incoming/"upstream" side. The way Walt said is my understanding of early CJ circuits.

Of course a PO may have done anything with the wires.

 

I agree, the fault must be between the power source (headlight breaker) and the switch, not the other side where the turn signal is.