Brake Light Switch

[demon69 13]

Hi 

Just replaced the brake light switch on my 69 Mach1, unfortunately, its no better than the one I replaced.  It is not sensitive enough to detect light peddle pressure, is there an adjustment that can be made or is there an alternative solution?

Thanks

Peter

[Brian Conway 279]

Two switches' available; one for power disc brakes C9ZZ-13480-B   SW-864 and non-power C9ZZ-13480-A   SW-863.  Brian

[RPM 1,268]

Hmm... anyone know the difference between the two? I kept the switch from the original power brakes when I went to manual, brake lights work the same, which is really good. 

[Brian Conway 279]

As I recall it was a switch 'spring tension' difference?   A description of the problem might help with a solution.  Some adjustment is possible but it is at the booster push rod.  Do you have a booster? Brian  

[demon69 13]

I have power disc and used C9ZZ-13480-B.  So the problem is, I apply the brakes lightly to a point where it will slow the car but the switch is not activated, I have to brake harder for the switch to activate.  So I can be in traffic slowing down but the driver behind wouldn't realise this because the brake lights are not activated.  I know of other owners have had this problem and done away with the switch and used a GM switch.......

Ditch the stupidly designed brake light switch & install a cheap universal switch (HQ/Chev). I mounted mine to a simple L bracket & strapped it to the steering column with two hose clamps. It's so much more reliable than the original & fully adjustable.

Or using a micro switch......

So the micro switch is wired as "normally closed" so that the circuit is complete when the switch is "relaxed". When the pedal is fully up it closes the switch and opens the circuit and keeps the lights off. Very slight movement of the pedal closes the circuit and puts the light on before there is any actual braking.

It's effectively fully adjustable by moving the point where its hose clamped to the column. Wiring wise I just made up an adaptor with some spade terminals to plug into the existing wiring plug that connects to the standard switch so nothing has been butchered and it's easily returnable to original condition (which is my case meant no brake lights). I left the old switch in place so there is no change in the relationship between the pedal and the master cylinder/booster rod.

However, I would prefer to get the factory switch to work more efficiently if this is possible.

Cheers

Peter

 

 

 

 

[Brian Conway 279]

I took a look at what's in my PDB car.  I am running the AUTOLITE C6OB-13480-A.  Can't explain the why or how but it works.  Maybe try a C9ZZ-13480-A switch and see what happens?  

[demon69 13]

Brian, does your brake light come on with a light touch of the brake peddle?

[aslanefe 352]

On 6/4/2022 at 4:01 AM, demon69 said:

Hi 

Just replaced the brake light switch on my 69 Mach1, unfortunately, its no better than the one I replaced.  It is not sensitive enough to detect light peddle pressure, is there an adjustment that can be made or is there an alternative solution?

Thanks

Peter

You can put a shim between the "cam" of the brake pedal and the switch and shorten the distance between the cam and switch.

[Brian Conway 279]

9 hours ago, demon69 said:

Brian, does your brake light come on with a light touch of the brake pedal?  Yes.  At the first hint of resistance.  Brian

 

[jmlay 92]

Peter,

Are the bushing and spacers installed with the switch?

https://www.npdlink.com/product/mounting-kit-brake-light-switch/185676/

[det0326 198]

I seem to remember, that on the Power assist brakes anyway, there is a slight amount of travel on the petal before the pushrod that goes through the firewall ever moves. That is the actual movement that activates the switch, if that movement is not there on yours that may be your problem. 

[maxum96 32]

I recently had the opposite problem, my brake lights were staying on.  I figured out it was my aftermarket brake pushrod I'd just installed.  The backside of the pushrod ring (where it attaches to your brake pedal) has a flat area.  This is what contacts the brake light switch and activates it.  In my case, the flat area was too thick and I just shaved it down about .030 to get the brake lights not to stick on.  I suspect you have the opposite issue,  too much play.  Check the plastic bushing the brake pushrod uses where it attaches to the pedal.  Perhaps you need to shim the brake light switch?  I saw this done and they used a piece of thin metal folded around the face of the brake switch contact area. 

 

[demon69 13]

Thank you everyone for your reply, appreciate the input.  FYI, I have now used both brake switched, the -A and the -B for the same result.  The guy who owned the car before me had the -A switch and had tried to shim it to make the brake switch work better but to no avail.  I was thinking the problem is the spring pressure in the switch is too high but there is nothing I can do about that.  I might try the shim method as outlined by Maxum96 but I'm still thinking the spring pressure is the problem.

I will let you know how it works out.

Cheers

[RPM 1,268]

On 6/5/2022 at 6:27 AM, jmlay said:

Peter,

Are the bushing and spacers installed with the switch?

https://www.npdlink.com/product/mounting-kit-brake-light-switch/185676/

Did you confirm this?

[demon69 13]

Yes, the bushing and spacers are installed with the switch

[Kris 90]

You may have the wrong pushrod on your master cylinder. When I replaced my master cylinder the rod it came with was the incorrect length. I took my the rod out of my original master cylinder and it works perfect. I had my wife test it yesterday with me watching the lights and if you touch the pedal basically at all the lights come on. 

[Project 69 1]

As mentioned before the switch for power brakes is more sensitive that the one for manual brakes, there is thread about this somewhere on the forum. A more drastic solution could be installing a proportioning valve combo unit that has an integrated fluid pressure switch like the one attached. I'm Installing one of these while I replace brake lines and plan to try it.

[AusTex70 78]

Iam battling this issue - any udate on this from @demon69

[Vicfreg 800]

I had this issue on my '68. The root cause was that my clutch pedal support bushings were worn out to the point where the pivot shaft had worn into the metal. This was causing the brake pedal to move around. I had to replace the clutch pedal support with one from an automatic transmission car, and now the original mechanical switch works fine.

On my '70, I had to install one of the Wilwood proportioning valves as I went with 4 wheel disc brakes.  I have a pressure switch, works every time.  I like this setup much better.

Vic

 

 

[69RavenConv 308]

On 12/20/2023 at 3:22 PM, AusTex70 said:

Iam battling this issue - any udate on this from @demon69

 

I just replaced mine this last summer. I tried the sheet metal shim on the OEM and it worked but ended up replacing it with a new one just to be safe. If the new one lasts 50 years like the old one it will be someone else's problem :)

My problem was the spring had fatigued to the point I had to stand on the brake pedal to get the lights to come on. The new one lights them with a very light touch. As mentioned above, there is a different switch for power brakes and non-power brakes, so make sure you get the correct one.

[AusTex70 78]

I was able to remove the old switch, it actually fell apart in pieces! 

While I wait for parts to arrive, I've rigged up a stop light switch I had laying around, and used a band clamp around the steering column. 

It's actually working great! Maybe I'll just leave it this way? :)

 

[69RavenConv 308]

Very clever! 

[Vicfreg 800]

Neat fix!

For sure would not leave it that way