1941 Brake light puzzle

[Jim Miller]

Took my '41 for a drive and discovered the brake lights remained lit though the pedal was not depressed. Brakes worked fine.  Arriving home, pulled car into garage. When I pulled the Ebrake the brake lights went off. So I tried it several times. Release Ebrake brake lights come on, pull Ebrake they go off. Appreciate any thoughts on where to start or what it may be.
Jim Miller

[wheikkila]

It sounds like a short in the wiring. The main harness is in the driverside by the emergency brake.
Thanks Wayne 

[Chris Cummings]

Hi Jim,

Sorry for your predicament.

What do the wires that connect to your brake light switch look like?  They sit there exposed to the elements and their insulation can easily become compromised.

Chris

[Bob Schuman]

Jim,
This message board is spooky. It locked me out twice before allowing my login. Below is what I was trying to write.

Problem is that the 41 is lonesome, you have been giving all of your attention to the 49 CDV. It just wants some love.

Seriously, there is no connection between the mechanical e brake and the brake lights. The e brake cable is inside an armored sheath that comes out of the firewall and curves around to connect to the linkage behind the transmission. That sheath is likely in contact with a bare wire on or near the brake light switch that is found on top of the front end of the master cylinder. In case you need a new switch, it is the same as used on Fords through 1964, should be available at NAPA.

[Jim Miller]

Thanks for the input. From my perspective the wires look good. I know they aren't original Bill Ingler and Bob Messinger rewired the car many years ago with all the correct tracing. I'll get her up on a rack where I can look closer. Now today it's working fine. But it was quite odd that pulling the ebrake turned the lights out. Pre-war gremlins.

[Bob Schuman]

Jim,
Still don't quite see how the e brake could affect the stoplight operation. Possibly it is a bad stoplight switch, with electrical contacts that sometimes stick closed for a while. I have never heard of this type of failure before, but have encountered and known of others who have had many stoplight switch failures, wherein the contacts burn from use and eventually fail to complete the circuit to the stoplights. After some investigation, I believe most, maybe all presently available replacement switches are electrically inferior to what was used years ago, so they fail early in life. Some persons believe silicone brake fluid is the culprit, but I am convinced that is not true.

Changing the switch, if that seems appropriate, does not require any brake bleeding with an original style master cylinder. With the Wilwood, I'm not sure, but likely also does not
involve bleeding, just unscrew the old and screw in the new switch.

[Jim Miller]

Thanks Bob
I've not crawled under yet. I have the Wilwood dual master cylinder and one of Art Gardners conversion brackets. I know it sounds nuts, but the brake lights did go out when I pulled the ebrake. Did it several times as I couldn't believe it either. To make it worse, not doing it today. Is it at all conceivable that there was enough pressure on the line, for some reason, that the brakes lights would not go off and that by pulling the ebrake it relieved the pressure and lights went out?

[Bob Schuman]

Jim,
This is a strange one, but you may be onto something. Possibly hydraulic pressure is being trapped when the brakes are released, and applying the handbrake moves the rear wheel shoes against the drum and away from the wheel cylinder pistons of one or both rear wheels.  Or possibly the master cylinder chamber that serves the rear wheels has a restriction preventing normal bleed off of pressure when the pedal is released.
Here are a couple of easy tests that may help find the culprit.
After the car as sat overnight,  heck brake pedal free play with your hand-should. E about 1/8 to 1/4 inch. Then press the brake pedal firmly and release. Recheck pedal free play, if it has noticeably increased something in the master cylinder is sticking,  of moving as it should.
Next test is for sticking rear wheel cylinders. Jack up so rear wheels are off the floor. With car in neutral, rotate rear wheels by hand to observe resistance to rotation. Press brake firmly and release, then quickly try rotating rear wheels. If effort is greater, wheel cylinders are sticky or something else is wrong with the freedom of the movement of the brake shoes.
If none of this leads to a solution, there are lots of smart persons on this message board, someone else may have a better theory.

[Bob Schuman]

Jim,
Spell check really screwed  up what I typed. I hope you can make sense of it

[Jim Miller]

Yes thanks

[Ohjai]

Is the brake switch a hydraulic pressure switch on a 41?  Or, is it  mechanical, with adjustment, could the parking brake cables be moving/activating the mechanical switch?


Jim

[Jim Miller]

Hydraulic switch. I did raise each rear wheel and checked spin before and after applying brake and also ebrake. They released immediately. Maybe just a fluke with the pressure. I'll keep watch. Pedal resistance felt like normal.

[Ohjai]

I was under my 38 60S yesterday and noticed the pressure switch on the back of the master cylinder.  The Parking Brake cable runs very close to the switch and if it were not secured, it would be possible for it to short across the brake switch.  Sorry I did not get a picture, I was involved in adjusting the clutch and did not think about a picture.


Jim

[fishnjim]

Sorry for the postwar incursion into the prewar space, but I follow some of these to learn.
Some what has been said does not make good sense.   
The circuit is working, ie, the brake light(s) come on.   Therefore, the pressure switch is doing it's job.   However, the pressure is not being relieved when the brake pedal is let up but is when the ebrake is engaged.  So somethings hanging up in the rear wheels.   I suspect when the ebrake is applied, the shoes are moved and the wheel cylinder lets off the pressure causing the lights to go out.   
If it's a short it has to be a very smart crafty one, just enough to put the lights out but not enough to blow the fuse.   That's not likely, folks.
I'd inspect the rears, and maybe adjust shows/lube wear points, and see if it goes away.   Could be the switch, if the contacts are hanging, but that failure mode is usually, not reversible.  Diaphragm broke wouldn't work at all.

[Jim Miller]

Solved my brake light puzzle. Not a short nor the switch. Adjusted the brake pedal and solved the problem.

[The Tassie Devil(le)]

Great news.   A simple fix.

Thanks for advising us.

Bruce.