View Full Version : Brakes: Can electricity engage the brakes?

07-26-2011, 08:51 AM
Hunting down the brake drag on my 55 Commander K. Sitting at a car show since 7 a.m. and a brake light came on all by itself when the ambient temperature started to spike over 85F. I drove it there and used the turn signals. My turn signal switch has been binding and acting up. Sometimes no brake light, sometimes one, no auto-cancel. Is it possible that a rogue signal getting to the brake light switch from the turn signals could actually engage the brakes? Could that switch act like a selenoid if it had power? Wierd or what?

07-26-2011, 09:05 AM
Remember, the brake light is a simple "hot" wire needing only a ground to activate the light. Normally, the pressure switch needs pressure to complete the circuit. The pressure overcomes the spring that holds the circuit "open" and creates a ground. If the spring has failed or weakened to the point that "thermal expansion" can cause the circuit to close as temperature rises, the circuit can close and cause the light to come on.

Another (and more likely) cause is a bare spot in the wiring shorting to ground, closing the circuit and causing the light to come on. Then there is the other possibility of a conductive fluid leak contaminating connections or a bare spot in the wiring causing a short to ground.

In any case, the least severe result is to drain your battery. The worst would be a dead short that could heat the wire causing a fire and burning the car up along with the building it is parked in.

Since the circuit should be protected by a fuse or breaker, hopefully, the worst result will not occur. However, you need to find the cause and correct it.

07-26-2011, 09:10 AM
Too eager to reply to you brake light problem...I failed to notice that you are also having a brake drag problem. You could be experiencing a mechanical adjustment problem such as improper master cylinder rod, hill holder release point(if equipped) , or master cylinder cap vent. Sorry for not reading more closely.:)

07-26-2011, 09:57 AM
1. No, electricity won't apply the brakes. (Well, I guess if you dumped enough juice into the master cylinder to heat it and boil the fluid, and if the relief port were blocked, it might, but you'd notice the smoke.)

2. The brake light switch has hot wire on one side, the other goes to the turn signal switch so the brake light signal can be sent to whichever rear lamp is not signaling a turn at the time. So a faulty turn signal switch can cause erratic brake light operation. But no grounds are switched. All the switching is in the hot side.

3. since you say you are getting brake drag, and the brake lights coming on, the simplest explanation is that pressure is being retained in the master cylinder. Pedal not coming up full to the rest position, push rod over-adjusted holding the m/c plunger in a little, or m/c plunger sticking in the bore. Swollen rubber cups in the m/c are also a possibility.

4. Next time it happens, just crack open a bleeder screw at any wheel, and see if the lamp goes out. If it does, trapped pressure in the m/c is indeed the problem.

5. Clogged brake lines or hoses can indeed cause brake drag, but usually the brake lamps don't stay on. because the brake lamp switch is at the master cylinder and the clog is "downstream."

6. Good news is, that if the master cylinder is bad, new ones are readily available from any of our vendors, or even your local FLAPS. They are still a popular type.

07-26-2011, 10:24 AM
Thanks, John and Gord. New M/C when we did the build 2000 miles ago. Put another new one in just to make sure. Replaced the 2000 mile new brake light switch with another new one and replaced the 2000 mile flex hoses with three new ones. All new steel lines and wheel cylinders. Yes, I can let the pressure off at a bleeder screw. As one drives and uses the brakes, the pressure builds and the pedal comes to the top and stays there. Your comment about the push rod rings true. Paul (55s) took her for a drive (only other person I have let take her for a drive) and he said the shoes were adjusted too close (from the feel). Wrong shoe adjustment or the M/C rod adjustment would have the same feel? I'll try again. Almost worth the airfare to fly you here for a test drive. I'll keep playing with it and keep you posted.

07-26-2011, 10:47 AM
OK. My shop next door re-adjusted shoes and M/C rod and after three short trips, no brake drag, yet. Left brake light still staying on, but pulled the steering wheel and we can get the light off if we manually hold the signal switch lever in a certain place. That was a signal switch I found on eBay and the wiring appeared pretty nice compared to the switch we pulled out. Appears the switch, itself, is wonky so....anybody have a decent signal light switch for a 6V C/K?

07-26-2011, 03:47 PM
Just took it on a longer drive on the 4-lane (85 mph). No brake issues, no more running hot issues, didn't notice the blow-by it had been showing, and feels like it would make it on a long trip. If I can replace that signal switch, I wouldn't need hand signals either. I have the original switch (before rerplacing it with the current one) I took out with the wires chewed. The switch itself seems smooth. Anyone ever tried to splice the signal wires AT THE SWITCH? If it can be done neatly with a little soldering, is it worth a shot?

07-26-2011, 05:19 PM
Dave, sounds like you are making good progress and learning a lot in the process.

I am too lazy to get into my literature to look for that switch number. I wonder how many were offered for the year. However, I would think someone out there has one. I have re-wired various switches and even rebuilt an overdrive relay. If you have the patience, tools, and know where to place a heat sink (if needed) you should be able to rewire that switch. If not, save it for someone who would be willing to tackle the job. Some of these old switches become too corroded to save but many can be cleaned and refurbished. The smaller switches take some good finger dexterity to neatly solder and restore to operable condition.

Good to see the progress on the brake problem, and good luck with the switch.:):cool::)

07-26-2011, 08:06 PM
Hi Dave when my 55 was giveing me trouble I called studebaker west and got a later year switch the only differance was color of some of the wires. But as I recall they had info to plug it in now I can drive at night and have both headlights and turn signals.

07-26-2011, 08:10 PM
Dave, unless I sold it and forgot. (heh) I should have a '55 signal switch out of a President coupe. But I won't be home for a couple of weeks.

Soldering and splicing new wires onto the signal switch ought to be easy enough. Use some new, Teflon-insulated wire, which will be much smaller than the old stuff, yet retain adequate current-carrying capacity. Will make it easier to snake through the column.

Tip: when pulling the old wires out, tape a piece of strong cord or string trimmer line to the end, so it can be used as a puller to drag the new wires back down.

07-26-2011, 08:54 PM
Hey Perry/Dave,

Thank you for being the first to try it! It was a pleasure to drive, and a beautiful car!

New brake light switches ae very available: NAPA SL134, Borg Warner S194, Standard Motor Parts SLS27, Harley (apparently best for silicone fluid - I use regular brake fluid) The Harley switch may have the wrong contacts, but works long time with silicone.

I thought your pedal was too high - mine has about 2-3 inches before brakes apply, but nice hard pedal.

07-30-2011, 01:29 PM
55coupe, thanks for the tip. Garage next door wired up the old switch and it's pooched, as well. I left a message at the Studebakers West site. Tried to call but it's Saturday and they're likely out driving Studebakers. Cheers!