Brake light switch kills engine

[TJMack]

I’ve got two stories about the brake light switch that I’ll share in hopes that someone else might benefit from what I learned by experience.

When I finally got the Garage Sale Model A running I decided it was time to see if it would drive, so I eased it around the block with no issues. After I got comfortable that it might go a little further I headed for a trip around two blocks at a slightly higher speed.

When I got to the first stop sign the engine quit when I put the brakes on. Of course I didn’t immediately relate the stoppage to the brakes going on so I went through the usual ritual of determining whether it was fuel or electrical related. I quickly discovered that there was no spark. I also discovered that nothing else electrical was working.

Somewhere along the line someone suggested that I install an in-line fuse on the main power wire when I was installing a new wiring harness.That was priceless guidance.

I found that the fuse was blown killing power to the coil and everything else. I thought maybe the fuse was too low amperage, but a replacement blew as I was putting it in. hhmmmm!

I mentally went through the steps I had taken before it stopped and concluded that the brake lights had blown the fuse. So I figured I would just disconnect the brake light wire from the brake light switch so I could get the car back home.

When I removed the floorboard and looked at the switch I immediately understood the problem. At this point in the resurrection of the car I hadn’t totally adjusted the brakes. When I applied them for the stop sign I had to push them quite a ways down to get the car to stop. This over pulled the stop light switch pulling the rod that goes down the middle of it too far out allowing it to drop and short out the circuit, blowing the fuse.

If it hadn’t been for that fuse the wiring would surely have cooked and who knows how much farther that disaster would have gone.

Once the brakes were properly adjusted I had no more problems until I let a friend of mine drive it one day. Needless to say he wasn’t used to mechanical brakes. When he had to make a quick stop at a stop light he pushed so hard on the pedal that the rod pulled out again, but this time only far enough to jam the brake linkage enough to make the brakes drag.

Since the engine didn’t quit this time I didn’t immediately suspect that stupid brake light switch. But with a quick removal of the floor board I could see that the problem was that the link between the brake pedal and the switch had caught just right to hold the brake pedal down enough to drag the brakes. Easily fixed for the ride home, but I knew I needed to do something different.

The solution was really quite simple. I put a spring (actually I had to use two short ones to get the exact length needed) in place of the culprit link. I also drilled a ¼” hole in a lead fishing sinker and crimped it onto the end of the shaft that sticks out of the brake light switch to act as a positive stop. This prevents the rod from being pulled out too far.

It works like a charm and I would suggest that you consider doing it to your car to prevent the issues I had. I know what some will say, “if everything is adjusted properly you don’t need anything like this.” That’s true, but everything isn’t always adjusted properly, and this is so simple and so sure of preventing what could present a serious situation, why not do it?

Take a look at the pictures. It’s easy to see what I did. The spring wants to be strong enough to overcome the one in the switch but soft enough to pull if the sinker limits the travel of the rod. The length of the spring needs to be exactly what the link is. I got mine at Lowe's.

[700rpm]

The farmer fix is alive and well!

[Bill G]

You can't argue with success. I might say that the switch looks new and the old linkage looks like it is quite old, and might not be a good match for the new switch. You might consider ordering a new link the next time you buy something from one of the suppliers, just in case the springs come apart.

I do like your ingenuity.

[1955cj5]

"Somewhere along the line someone suggested that I install an in-line fuse on the main power wire when I was installing a new wiring harness .That was priceless guidance"

I forget who this unfortunate fellow was......a fuse or battery cut-off switch might have made a difference...


.

[F.M.]

Originally Posted by TJMack

I’ve got two stories about the brake light switch that I’ll share in hopes that someone else might benefit from what I learned by experience.

When I finally got the Garage Sale Model A running I decided it was time to see if it would drive, so I eased it around the block with no issues. After I got comfortable that it might go a little further I headed for a trip around two blocks at a slightly higher speed.

When I got to the first stop sign the engine quit when I put the brakes on. Of course I didn’t immediately relate the stoppage to the brakes going on so I went through the usual ritual of determining whether it was fuel or electrical related. I quickly discovered that there was no spark. I also discovered that nothing else electrical was working.

Somewhere along the line someone suggested that I install an in-line fuse on the main power wire when I was installing a new wiring harness.That was priceless guidance.

I found that the fuse was blown killing power to the coil and everything else. I thought maybe the fuse was too low amperage, but a replacement blew as I was putting it in. hhmmmm!

I mentally went through the steps I had taken before it stopped and concluded that the brake lights had blown the fuse. So I figured I would just disconnect the brake light wire from the brake light switch so I could get the car back home.

When I removed the floorboard and looked at the switch I immediately understood the problem. At this point in the resurrection of the car I hadn’t totally adjusted the brakes. When I applied them for the stop sign I had to push them quite a ways down to get the car to stop. This over pulled the stop light switch pulling the rod that goes down the middle of it too far out allowing it to drop and short out the circuit, blowing the fuse.

If it hadn’t been for that fuse the wiring would surely have cooked and who knows how much farther that disaster would have gone.

Once the brakes were properly adjusted I had no more problems until I let a friend of mine drive it one day. Needless to say he wasn’t used to mechanical brakes. When he had to make a quick stop at a stop light he pushed so hard on the pedal that the rod pulled out again, but this time only far enough to jam the brake linkage enough to make the brakes drag.

Since the engine didn’t quit this time I didn’t immediately suspect that stupid brake light switch. But with a quick removal of the floor board I could see that the problem was that the link between the brake pedal and the switch had caught just right to hold the brake pedal down enough to drag the brakes. Easily fixed for the ride home, but I knew I needed to do something different.

The solution was really quite simple. I put a spring (actually I had to use two short ones to get the exact length needed) in place of the culprit link. I also drilled a ¼” hole in a lead fishing sinker and crimped it onto the end of the shaft that sticks out of the brake light switch to act as a positive stop. This prevents the rod from being pulled out too far.

It works like a charm and I would suggest that you consider doing it to your car to prevent the issues I had. I know what some will say, “if everything is adjusted properly you don’t need anything like this.” That’s true, but everything isn’t always adjusted properly, and this is so simple and so sure of preventing what could present a serious situation, why not do it?

Take a look at the pictures. It’s easy to see what I did. The spring wants to be strong enough to overcome the one in the switch but soft enough to pull if the sinker limits the travel of the rod. The length of the spring needs to be exactly what the link is. I got mine at Lowe's.

I see five things just looking to happen very soon in the pictures..

[700rpm]

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Originally Posted by F.M.

I see five things just looking to happen very soon in the pictures..

I don’t see five things, but I’d get that battery secured before it wears through the wiring. And that rusty brake rod... needs attention!(at least)

[TJMack]

Originally Posted by F.M.

I see five things just looking to happen very soon in the pictures..

This is the kind of dumb post that ruins forums. Nothing positive to say just kibitzing. (look up the definition of that if you don't already know what it means) Compare it to the positive input from 700 RPM right below it. BTW, 700 RPM, the picture just wasn't wide enough to show the corner hold-downs.


See attached.