VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Placement of Mechanical Brake Light Switch

I have a mechanical brake light switch I need to install on my '41 Special Deluxe. The hydraulic one has never worked and, from what I've read on these forums, the mechanical switch is the best option for a replacement.

When I look under the hood at were I could mount it to the firewall, I don't see a whole lot of space in there next to the brake peddle lever. Looks like it will be difficult at best unless I take the hood and left fender off, which I really don't want to do at this point.

I'm sure a lot of people on this forum have replaced their old hydraulic switch with a mechanical one. Where/how did you install it?

Just looking for some good advice before I mount it, find out it's in a bad place, and then have to move it.

I drilled the holes from the passenger compartment side. I pulled the floor mat back & worked from there. I eyeballed the switch location & marked the holes using the switch itself as the template. Once they were drilled I had the skinny arm wife hold the switch in place in the engine compartment while I drove the self tapping screws from inside the car. I ran jumper wires to the OEM wires by the old switch.

That looks good. My daughter has the skinniest arms so I may have to enlist her help.

It looks like you used a piece of vacuum hose over the switch arm. Was that to help with wear and tear, noise, or travel distance?

I have never had much trouble with the original hydraulic switches. I think I have replaced one in the many years I have had old cars.

The 1942 and up had a lever type switch and the floor/pedal area is the same as a 1941. See page 12-31 of the 1942-1946 shop manual see old car shopmanual project for picture/manual.
oldonlime chev manuals

You must use the 1942 car switch as some other applications are reversed.

Fine tuning the travel distance.

Bj,

Please don't change the switch out. Do the following:

a. See if you're getting juice to the switch.

b. If you're getting juice at the switch, have someone mash the brakes and see if there is juice to the other terminal. If so, read on.

c. If brake light bulbs are good and still no brake lights trace the wires.

d. If determined that the switch is bad, order a new one that takes the pig tails that slip on.

e. Until you get the switch, use your hand signal to indicate you're slowing down or going to stop.

The reason for pleading for the original switch is that it is reliable and is not hard to install as the lever one is and is very reliable for long periods of time and do't get in the way whenever you have to fiddle under the dash.

Best,

Charlie

It is not under the dash.
The original hydraulic switch goes bad often when Dot 5 brake fluid is used. Also when adjusted correctly the lever switch lights the brake lights faster as it doesnt wait until hydraulic pressure turns the lights on.

I was having to replace hydraulic switches about every other year. The pressure switches would get to the point where I'd almost have to lock the brakes to get the switch to activate the brake lights. I'm assuming it's the quality of the imported switches at fault. The mechanical switch was the answer for me.

In my years of experince owning 41s only once has my switch gone out. One can find the things everywhere. Dot 5 mauy have a negative effect on them but I've always used Dot3.

How much faster does one need the brake lights to come on anyway? The regular switch is fast enough.

I was wrong about the mechanical unit being under the dash. Thanks, Gene.

If one has to lock the brakes to activate the brake lights using the original type switch then something else is wrong otherr than the switch.

BJ don't listen to these guys. They probably sell those stinkin mechanical switches. Let me know if you need and original one.

Best,

Charlie

That makes no sense at all Charlie. Please explain.

"The pressure switches would get to the point where I'd almost have to lock the brakes to get the switch to activate the brake lights."

Tiny, I was merely feeding off your statement cited above. Seems to me it would be difficult for the driver to know when the brake lights come on. I can tell by the slight negative change in ampmeter as the switch draws power. If that is what you do then how do you know if the switch is the sole culprit?

Maybe I've misunderstood your statement.

It seems to me and owing to my experience that the switch is either good or bad. No in-between.

Respectively,

Charlie

Great discussion and relevant to my plans for "winter" projects on my '37.

I drive the car in traffic frequently. I am going to add a mechanical switch like Tiny did so the brake lights will predictably come on sooner. I will wire it in parallel with the hydraulic switch.

I have observed various issues with the hydraulic pressure switch.

You cannot determine the activation pressure of a switch by looking a it or by the part number. Most suppliers think they are all the same. Based on the information I have seen the GM switches in our era cars should activate at about 30 psi. There are a couple of variations of the switches that Ford used (60 and 100 PSI). Today you can find a wide range of ratings. And the "low pressure" label is very misleading. One company uses it for 20 - 50 psi. Another says their low pressure is 55-120 psi.

In same cases I have been able to make the switch respond more quickly by bleeding it at the master cylinder. You can actually trap an air bubble in that cavity if you install the switch before you fill the master cylinder.

The longevity of the switches is a crap shoot. The key is how long before fluid leaks into the contact chamber. As more fluid leaks into that chamber it takes more pressure to activate the switch. Once that chamber is full of fluid the plate will not be able to move to make contact. Typically you can spot this because fluid will start leaking out around area where the insulator is crimped into the switch housing.

Rusty it is a pretty simple fix for your problem.
You need to mount a spring lever brake switch on the brake pedal arm.
Here is one of many types that could work with your situation!
Jegs Link: https://www.jegs.com/i/Allstar-Performance/049/ALL76250/10002/-1
Rory
1934 Chevy Holden Roadster Stock Original
1933 Ford 3 window Hot Rod
And a few other 33 and 34 Ford Hot Rods
Ps: You might get some points taken off at car shows for safety!

The main point against the use of the lever switch is that it's not original. Mounting it would be a modification. So where does modifications stop. Pretty soon you have a title for a 37 and all the bells and whistles of a modern Cadillac.

I'm a purist and want to keep my cars as original as possible.

Please don't argue with me about any safety issues associated with the lever switch over the pressure one. No such argument will persuade me. And, please don't offer the worn out expression, "it's only original once." That too won't persuade me and will likely make me puke. Will too!

Charlie

BTW: Just got back from O'rielys. They ordered the MC repair kit this morning and I picked it up this afternoon. With military discount: $20.00 and change.

Charlie, what would happen is a fellow driver would pull up next to me and tell me my brake light isn't working. I'd think it's only been a year since I replace it then have the wife press the brake pedal while I look. No light until she's standing on the pedal. When freshly replaced the lightest pressure would light it up. No air bubble or it would have been an issue all along. After three replacement pressure switches all doing the same thing after only a year or so I had enough and bypassed it with the mechanical switch. Original or no, with only one tail/brake light, I damn sure want it working.

Hey Charlie you are out cruising with you Purist 41 Chevy. You have an emergency stop your brake lights are delayed and you cause a 20 car pile up! Hey your car is all stock and original because you are a Purist with safety not being a priority. Go Figure???
Rory
1934 Chevy Holden Roadster Stock original
1933 Ford 3 window Hot Rod
And a few other 33 and 34 Ford Hot Rods

Tiny,

Please don't get upset. Doing so creates bile which causes indigestion. Not good.

As to the switch, I suppose one could talk one's self into modifying any system that repeatedly fails them. You have done so by adding a mechanical switch. Ok by me. Your car..

I continue to think that the switches are better than they are being given credit for. But that, apparently, is just me. There doesn't seem to be much support for the pressure switch.

You could add a second tail light and then you would have twice as many tail lights not working. Or working.

You can use your arm signal, too. Does your window roll down? Have you added electric windows. You may never know when you would want to get out of the car in more of a hurry than winding the crank will permit.

I support your decision to go the mechanical route. Not what I would do but your have better sense than me. I'll continue to be hardheaded.

Best,

Charlie

Modern hydraulic brake switch replacements are junk, IMO!

I installed an original switch in my '37 Sports Coupe in 1992 when I switched brake fluid ove to DOT 5 and through lots of touring and thousands of miles in the last 25+ years, it's still working perfectly well.

I've been told that Harley-Davidson has a switch that works well and lasts. You might give one of those a try.

I guess it is all what you are comfortable with, My '33 coupe has an original mechanical switch, my '37 Master has a hydraulic switch (I think I replaced it once), I am not sure what type of switch my '48 Fleetline has as I have never had a problem with it.

Your 48 should have the mechanical switch. I had to replace mine when I rewired my 48 coupe.

Roara,

Funny.

Two things:

a. There may be many who are concerned for, and driven by, defending their decision to modify their vehicle and then offer lame excuses claiming it is a safety issue.

b. There may be many whose pre-hydrolic cars wouldn't be able to stop fast enough to cause any disorder behind them even if followed by s freight train.

There is no point in scoffing at someone who likes to keep their car as original as they can. That is one of the basic premises of the VCCA. Safety is often misused as an excuse for some modifications. Defending such decisions by conjuring up chaotic , wild senerios may breed unsuportabe and insensitive comments.

Just saying.

Charlie

Here is a link that, according to someone, may describe what can happen if the brake light(s) are delayed in coming on. No need to whatch the whole thing. You'll get the picture soon enough. Must have been caused by a 41 Chevrolet driver doing an emergency stop owing to a Pronghorn crossing the interstate. Dang!

This is a timely thread as my hydraulic stop light switch has failed and I purchased a new one. My question is when I remove the old switch to replace it, will it leak brake fluid and will I possibly need to bleed the system? Thanks Bumper

No, just remove it fast and thread the new one in. Have master cylinder full before doing.

That's the way t did it last week. It works just fine..

Charlie