VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Hydrualic Brake light switch

The other day my son was following me as I drove my '39 Chevy Master Deluxe. He told me that my brake lights never came on. I was surprised in that I had a relatively new brake light switch on the master cylinder. At home I really pressed on the brake pedal and the lights came on, but this would be a panic stop, not a normal slow down. I think I got the switch from Chev's of the Forties. I have to replace it, but if I purchase another from the same place, I may just get another high pressure activated switch. Any suggestions as to where I can get a good switch. I emailed Chev's of the 40"s and they did not reply.
Thanks Mike

Try NAPA

Thanks, I give them a try. I suspect that the switch probably was the same up through the early 60's.
Mike

Take your old one with you. There are switches that have a push on stud for the wires and switches that have a screw lug. If you take yours with you for reference it can save an extra trip. BTW any FLAPS (Friendly Local Auto Parts Store) should be able to order your switch if you don't have a NAPA close by. Our local Bumper To Bumper keeps them in stock.

NAPA

I imagine that you replaced the switch because the old one wasn't working right... Since the new one isn't working right either, perhaps there is a blockage in the master cylinder where it connects? Perhaps pull the switch off and put in a fitting with a short piece of hose like for bleeding the brakes. Run the hose into a can or jar and have someone push down on the brake pedal so you can see if fluid is coming out well under pressure. And look inside the hole in the switch to see if you can see any crud in there. Has your master cylinder been flushed or rebuilt any time recently?

I cured the brake light switch problem in my "39 by replacing the hydraulic switch with a lever type switch that Chevrolet used from 1942-1954.
I was replacing the hyd. switch every few years for the same reason. Took very hig pedal pressure to make the lights work. I also have silicone brake fluid in the system. From what I have read the silicone builds up a film on the contacts and insulates them.
To install a lever swich see a picture in the 1942 and up shop manual. The switch mounts onder the toe bpard and it is necessary to drill two small holes to mount. It can be "adjusted" to have the lights come on with a very small movement of the brake pedal. To adjust slipping a small piece of rubber hose over the lever is one way to do it.

Is this the one you're referring to Gene? I've had to replace mine several times for this same issue. I might do this modification to mine.

There are about three varaitions of that switch. All can be made to work easily. I would go to NAPA or? and order a swich for a 1954 Chevrolet car.
On mine the wires were also te correct length and used the same terminals.

Harley Davidson uses a hydraulic switch and it is made to use with silicone brake fluid which is used in all Harleys. After having the same problems I have read about on here on this "post", that's the route I took and have had no problems with it. Works great!

Thanks Gene, a '54 car it is.

Well..... I went to NAPA, but the guy I usually work with was not there and the kid didn't know what to do, so maybe I'll try again at some later date. While I am waiting I looked through my old spare parts and came across a half dozen old switches. After cleaning them up and getting the screws out, I connected up some compressed air with a regulator and gauge to check them out. Some switches would not close at 120# air, but I found one that would close it's contact at around 75#. Some time today, I'll get under the car and change out the switch and give it the acid test. I may rig up a spare master cylinder to get more pressure and test the others, I suspect that the others may also work, but at a higher pressure. I'll also try to get a later model switch and see how that works. I appreciate the help, Thanks Mike

If you are alone and don't have a shop helper, here is a tip to install the lever brake light switch. After you get the holes drilled, cut the ends of a couple of 10/32 (I believe that is the correct size)bolts that are about an inch and a half or so long. Screw those into the switch. Put a flashlight inside the car to shine on the holes. You will be able to see the holes from under neath the hood and can put the switch with the 10/32 bolts up through the holes. If you hold your mouth right, the threads will grasp the floor pan enough to hold the switch until you can get into the car with a pair of vice grips and clamp on to one of the bolts. Take one bolt out and secure the switch with the proper length screw. Replace the other bolt and walla, the switch is in place. This is how I replaced the switch in my '48. Beamer

Beamer, thanks for the idea. I am familiar with the lever switches. I had one on my '26 Model T until I fitted it with disc brakes. It work good and was very reliable. I just got out from under the car. I had forgotten how difficult those little screws are. I'd just get my meat hooks in there a a cramp would cause me to jump away. I got the other switch in and it work a lot better. The old switch had definitely failed. One of the screw perches is loose and I suspect that the switch actually works but the contact to the wire would not make up. The old switch has a number on it HD76-133, but I can not find it listed anywhere. I did look up NAPA on the web and they do have a replacement, two in fact. Both for under $20. I'll probably get one for a spare. Thanks again for all the help. Mike

I can see the wisdom in converting the brake light switch over to the lever type used on later models. That said, I wonder if it's worth it.

a, There ain't nobody going to be following a 41, say, for any distance anyway. first chance they (other motorists) get they will pass you. Usually for no more reason than they think an old car can't possibly be doing the speed limit or a pride thing, i.e. just because they can.

b. In urban traffic situations, situations other drivers will be guided by what the mass of motorists (peloton. I thought I'd just throw that in) is doing and not paying any attention to your measly little old brake lights. Besides, if they are being alert and not on the their mobiles or texting, they can plainly see that you're are slowing down at a faster rate than coasting would produce.

c. If you are on a hill where there is a stop light, they will pull up so close on you that your brake light can't be seen anyway and they will be guided by the stop light anyway.

d. If you are out in the country and the driver is at a pace of a car-length for every 5 mph then they will be able to see your brake lights just before you hit the deer. Either switch. You get the picture.

So why, I ask you, is the compelling reason to convert to an add on mechanism that is not going to make you safer and one that you have to drill holes and hold your tongue to install? (See Beamer) Don't make no sense. Well, not enough to justify it, that is.

Has anyone ever been rear ended or been given the bird owing to the microsecond of time it takes the hydraulic switch to work? I didn't think so.

I ain't drilling no extra holes. Two more on the projetct will hardly be noticed but why add more.

Charlie

If you live in a large city you can not have enough brake lights.....and it is the law.

"If you live in a large city you can not have enough brake lights.....and it is the law."

Gene,

Please explain.

The fact that a mechanical switch may or may not complete a circuit activating brake lights quicker than the hydraulic one has nothing to do with "enough brake light" or any law that I've ever heard of. Are you referring to some sort of threshold of candlepower or quickness of brake light switch established by a state law? If so, what and where.

I need to be enlightened here. If I driving around with my relatively quick working original brake circuitry in violation of the law, I'd like to know about it. Big city or not. Is there some such law in WI.

Without more, your comment is somewhat puzzling.

Best,
Charlie

If properly adjusted the mechanical switch activates the light with the slightest movement of the pedal.
The hydraulic switch does not activate the light till a predetermined amount of (hyd) pressure is applied.
Chevrolet even stressed this in some of their advertising.On my 1939, which is converted, and my 1950 you see see the ammeter drop with the slightest touch of the pedal, well before the brakes are applied.

hi i have a 39 changed switch to on with a spring which is on to the brake pedal the hydrualic one was the same as yours the brakes would be full on before lights worked no good

I have a mechanical switch on the way. Better brake lights are in my future.

I had the same problem with my 1940. Brought the first one from NAPA. It failed in a month. Brought another from Chevy's of the 40's and it has been ok. I push the brake peddel with the key off and the ampmeter will discharge so then I know it is most likely working.

I am curious because some of the vendors sell what is described as a low pressure hydraulic brake switch. Has anyone usedone of these?

My experience with the low pressure switch is that they work for awhile and then quit. Just like all of the others.
The Harley switch I mention in an earlier post has been working for a few years now with no problems.

I have one on my car now. Over time they require higher pressure. I'm going to convert to mechanical because even the "low" pressure switch requires the brakes to already be engaged before the brake light comes on. With the mechanical switch the brake light will be on before the brakes are activated which will give following cars a tad more warning that my slow moving vehicle is about to get even slower.

To all,

There is not now nor has there ever been any doubt in my mind that the mechanical switch can give a faster brake light action. Although, by itself, it doesn't necessarily give a brighter brake light.

The first person that I can remember who indicated they had installed one on an earlier car than they came on was Gene when he referred to having put one on his 39 some years ago. I think he pioneered the concept here on the Chat and I think it is a good idea.

I haven't done it yet but will likely do so.

I just wanted the above to be clear.

Charlie