Brake light switch

[colbs]

I need to replace the brake light switch on my '48 royal but it's the original inl8ne switch thats activated via the brake fluid and I was wondering how the switch worked if it was truly fluid activated or it it had an air gap in it (in other words do I need to bleed the brakes when I replace the switch?)

[Tom Skinner]

I just changed mine out. Now if your Brake Pedal is mushy you may need to. If I recollect correctly I bled mine not long after changing it out.

You may not need to but its always good to bleed them every couple of years anyhow.

[Sam Buchanan]

I recently replaced the switch due to leakage. But I don't like the new one, erratic and requires too much pressure to activate. I'm going with a mechanical switch so I can set how much pedal travel turns on the brake lights. I want the lights to go on with very little pedal travel. This will require fabricating a bracket under the floor but should be worth the effort. I'll replace the present switch with a pipe plug so leaks won't reoccur.

 

To address the original question, I didn't need to bleed the brakes after replacing the switch. I had the switch ready to go and quickly swapped out the switches with very little loss of fluid.

Edited June 21, 2023 by Sam Buchanan

[colbs]

Thanks! I appreciate the answers! I'm hoping everything will work out with this switch!

[FarmerJon]

My switch didn't work when I first got the car. I replaced it, and it seemed to work fine.

One day a friend was driving behind me and told me my lights weren't working,  except when I stopped on a hill.

Turns out the factory style switch needs more pressure than I use in 80% of normal driving.

 

That next weekend I installed a mechanical switch. It is from a '50 chevrolet, available new everywhere. It has its own mounting bracket, so I was able to just attach it to the floor pan with a couple small bolts. 

[Sam Buchanan]

17 minutes ago, FarmerJon said:

My switch didn't work when I first got the car. I replaced it, and it seemed to work fine.

One day a friend was driving behind me and told me my lights weren't working,  except when I stopped on a hill.

Turns out the factory style switch needs more pressure than I use in 80% of normal driving.

 

That next weekend I installed a mechanical switch. It is from a '50 chevrolet, available new everywhere. It has its own mounting bracket, so I was able to just attach it to the floor pan with a couple small bolts. 

 

That is the same switch I have coming. And I'm going to a mechanical switch for the same reasons you did. The way drivers tailgate these days I want to give as much warning as possible that the P15 is about to have its great speed arrested.  ?

[Plymouthy Adams]

just pull a lever and drop a boat anchor on a chain....they will back off if just to photograph the sparks......lol

[Bryan G]

I replaced mine with one designed to activate at a lower pressure; I think an old Jeep application? A bit of net searching should find it for you. The wiring connectors were different but it works well. I believe in this case I had installed it prior to bleeding but I've installed one on another vehicle without having to bleed. Just have to be quick

 

[Adam H P15 D30]

20 hours ago, Sam Buchanan said:

I recently replaced the switch due to leakage. But I don't like the new one, erratic and requires too much pressure to activate. I'm going with a mechanical switch so I can set how much pedal travel turns on the brake lights. I want the lights to go on with very little pedal travel. This will require fabricating a bracket under the floor but should be worth the effort. I'll replace the present switch with a pipe plug so leaks won't reoccur.

 

To address the original question, I didn't need to bleed the brakes after replacing the switch. I had the switch ready to go and quickly swapped out the switches with very little loss of fluid.

There's a low pressure switch available for this exact reason.

[Bob Ritter]

To answer your question it is pressure active, just like the wheel cylinders. You could leave the old one in and mount a manual one which are more accurate and just switch the wires. The one like, one of our Mopar brothers showed are more common.

[Sam Buchanan]

3 hours ago, Adam H P15 D30 said:

There's a low pressure switch available for this exact reason.

True, but I like being able to set exactly when the lights are activated. 

[Los_Control]

I did a Master Cylinder swap on my truck plus new lines .... so I added a T in the line to move my switch to .... it was installed on original MC.

 

I started looking around for the brass adapter to make it work. I quickly realized I may not find the correct adapter to match the threads on the switch.

I might need to get 2 adapters to get to correct threads, or buy a new switch with different threads so I can adapt to the 5/16" T ....

 

Or simply go with a mechanical switch & get on with my day.

[Dartgame]

I replaced mine when I upgraded to disc brakes. It failed not too long afterwards. Part was from the usual suspect country of origin...I sought out several NOS switches, in this case motorcraft (Ford). So far so good. I keep a spare in the glove box, and the correct socket for it...Ford used these switches for a good amount time in the 60's and maybe 70's so finding an NOS switch is not a huge issue. Ebay is your friend.

[Sniper]

Ford uses a similar switch in their cruise control circuit to turn off the cruise when the brakes are applied.

 

Those have been the cause of many, many fires because Ford, in their infinite wisdom, decided it needed to be hot all the time, even when parked and the key in your pocket.

 

Had a coworker almost lose his F-150 due to this thing.  He was fortunate in two cases here.  One, I was standing in front of his truck having a smoke when it started and I noticed the smoke, I ram inside grabbed a fire extinguisher and two, he left the truck unlocked so I was able to open the hood and put it out. 

 

The most interesting thing about it was that he'd already had the recall done to "fix" this issue.

 

My coworker was up a wind turbine with the keys in his pocket when it occurred.

 

So I'd pass on using a Ford switch myself.

[vintage6t]

On 6/22/2023 at 8:08 PM, Sniper said:

Ford uses a similar switch in their cruise control circuit to turn off the cruise when the brakes are applied.

 

Those have been the cause of many, many fires because Ford, in their infinite wisdom, decided it needed to be hot all the time, even when parked and the key in your pocket.

 

Had a coworker almost lose his F-150 due to this thing.  He was fortunate in two cases here.  One, I was standing in front of his truck having a smoke when it started and I noticed the smoke, I ram inside grabbed a fire extinguisher and two, he left the truck unlocked so I was able to open the hood and put it out. 

 

The most interesting thing about it was that he'd already had the recall done to "fix" this issue.

 

My coworker was up a wind turbine with the keys in his pocket when it occurred.

 

So I'd pass on using a Ford switch myself.

 

Yup. Almost lost my F250 the same way. Parked in my driveway, one of the kids noticed the headlights were on. I went out side and smelled something burning under the hood. Luckily I was able to quickly disconnect the battery.  Probably just seconds or minutes from the truck going up in flames. Why were the headlights on? Because the wiring harness as in the process of completely melting down. The culprit, the switch Sniper is referring too.

 

One insurance claim and a completely new underhood wiring harness later it was fixed.

 

In general pressure switches are problematic, just change to a mechanical and be done with it.

[Sam Buchanan]

Got the SLS40 mechanical stoplight switch installed, it works just as I was hoping it would. The install was simple, I removed the floorpan to make it easier to access but it can be done with the pan in place if an extra set of hands are available. When the pedal is depressed the switch arm rotates and closes the switch turning on the lights. They activate after about an inch of pedal travel well before the master cylinder kicks in. I like it.

 

I intend to remove the new pressure switch (which didn't work as I wanted it to) to eliminate the possibility of the switch developing a leak like the old one did. The wires going to the old switch are long enough to reach the mechanical switch with no splicing necessary. I'll just need to remember to disconnect the wires from the switch if the floorpan needs to be removed.

 

 

[DonaldSmith]

Of course, I have to take things to extremes, like easy access to the mechanical brake switch.  But I also have the Jiffy Jet bulb under the floor .  So I cobbled a removable part of the floor pan.   

(Shown hers, with the main panel removed.)

(Jiffy Jet plunger, between the pedal arms, pedals off.  Mechanical brake switch arm and red wires, below the panel.) 

 

 

[rcl700]

On 6/26/2023 at 5:01 PM, Sam Buchanan said:

Got the SLS40 mechanical stoplight switch installed, it works just as I was hoping it would. The install was simple, I removed the floorpan to make it easier to access but it can be done with the pan in place if an extra set of hands are available. When the pedal is depressed the switch arm rotates and closes the switch turning on the lights. They activate after about an inch of pedal travel well before the master cylinder kicks in. I like it.

 

I intend to remove the new pressure switch (which didn't work as I wanted it to) to eliminate the possibility of the switch developing a leak like the old one did. The wires going to the old switch are long enough to reach the mechanical switch with no splicing necessary. I'll just need to remember to disconnect the wires from the switch if the floorpan needs to be removed.

 

 

Any way you can post a few additional photos of the placement of this and how you mounted it? 

How is the sensitivity set on this type of switch? 

Thanks in advance 

Edited July 3, 2023 by rcl700

[Sam Buchanan]

19 minutes ago, rcl700 said:

Any way you can post a few additional photos of the placement of this and how you mounted it? 

How is the sensitivity set on this type of switch? 

Thanks in advance 

 

 

The photo I posted is about all there is to the installation. The switch has two threaded holes so a couple of screws can be used to attach it to the floor board. The switch is activated as the arm swings through an arc which is not adjustable. If adjustability is needed it is achieved by tweaking the switch attachment. In my case it works great as shown with no tweaking needed, the lights come on when the pedal is depressed about an inch. I don't know how to make this any more complicated. 

 

[Los_Control]

Just now, Sam Buchanan said:

the lights come on when the pedal is depressed about an inch. I don't know how to make this any more complicated. 

Beer .... If we hand out free beer it complicates everything  

 

[rcl700]

7 minutes ago, Sam Buchanan said:

 

 

The photo I posted is about all there is to the installation. The switch has two threaded holes so a couple of screws can be used to attach it to the floor board. The switch is activated as the arm swings through an arc which is not adjustable. If adjustability is needed it is achieved by tweaking the switch attachment. In my case it works great as shown with no tweaking needed, the lights come on when the pedal is depressed about an inch. I don't know how to make this any more complicated. 

 

Thank you for replying. 

I was trying to understand if the placement was in the engine compartment or the cab side. The picture looks to be on the firewall on the engine side. Did you drill holes and run small bolt from inside under the carpet to outside to secure the switch with nuts? 

[Sam Buchanan]

11 minutes ago, rcl700 said:

Thank you for replying. 

I was trying to understand if the placement was in the engine compartment or the cab side. The picture looks to be on the firewall on the engine side. Did you drill holes and run small bolt from inside under the carpet to outside to secure the switch with nuts? 

 

No...as stated the switch is attached to the floorboard. The arm you see over the switch is the brake pedal under the floor. Also as stated...the holes in the switch are threaded so no nuts are needed. Be advised the threads are metric, but two small screws are all that is necessary to mount the switch to the floorboard. When you look under your car this will be more apparent. 

[Los_Control]

Maybe I can help, I have a truck & not a car ..... The brake & clutch pedal rest on the underside of the toe boards.

This means the toe boards are the definitive answer to the position of the pedal.

So drilling the holes & mounting the switch on the underside of the toe board is the ideal spot for me.

 

As @Sam Buchanan suggest, pick proper placement & no adjustment needed.

You just want to mount it where the switch sits comfortably in a off position, then when you move the pedal it goes to on position.

 

Because the previous link showed a chebby switch with a mounting bracket, just makes things easier.

 

If you have under the floor pedals, you will need to mount the switch under the floor.

[Sam Buchanan]

rc1700 has the same car as I so his installation should be identical to mine.

[colbs]

I honestly will probably by the mechanical switch especially seeing as how the switch I have to replace has the female connectors and so does my wiring harness I appreciate everything as always guys! Hopefully I can slow down long enough to work on her soon!