Brake light switch

Discussion in 'Classic Mustang Specific Tech' started by Mach1 Ian, Jul 18, 2008.


  1. Mach1 Ian

    Mach1 Ian New Member

    Joined:
    Nov 15, 2006
    Messages:
    37
    Likes Received:
    0
    Trophy Points:
    0
    Location:
    United Kingdom
    Is there any adjustment on a 70 brake light switch? When i had a SSBC disc conversion fitted i ordered a power switch and pedal, correct parts fitted. The problem is, to activate the brake lights you have really press the brake pedal hard enough for an emergency stop, gentle braking and the lights don't come on.
    I have looked at the switch but as far as i can see there isn't any adjustment or could it be a faulty switch?
    Any help welcomed by a U.K. Mach1 owner
    Thanks
    Ian
    #1
  2. zookeeper

    zookeeper Founding Member

    Joined:
    Aug 25, 2001
    Messages:
    3,169
    Likes Received:
    3
    Trophy Points:
    59
    Location:
    Northern California
    I had a similar problem on my '68, which I think is the same as your '70. The rear of the master cylinder pushrod has a vertical, flat surface which contacts the brakelight switch. The problem is that no two pushrods are the same, and even a variation af a few thousandths changes the contct point of the switch. So what you need to do is remove the switch and use needle-nose pliars to GENTLY bend the tangs on the switch where the pushrod contacts it. It's trial and error, but not hard and if you'd like, I'll post a picture later of where to do the bending. Hope this helps! Jim
    #2
  3. Mach1 Ian

    Mach1 Ian New Member

    Joined:
    Nov 15, 2006
    Messages:
    37
    Likes Received:
    0
    Trophy Points:
    0
    Location:
    United Kingdom
    Hi Jim
    Thanks, it would be a great help if you could post a picture, then i can get the problem sorted as it is getting embarrassing having other drivers telling me that my brake lights aren't working.

    Thanks
    Ian
    #3
  4. zookeeper

    zookeeper Founding Member

    Joined:
    Aug 25, 2001
    Messages:
    3,169
    Likes Received:
    3
    Trophy Points:
    59
    Location:
    Northern California
    Ian, to show you just how easy it is to R&R the switch, I removed it for the pictures in less than a minute, took the pics and had it back in the car, all in less than 3 minutes. Why? Because I had it out about 10 times to get the tabs bent into the correct position last week. It takes a bit of fiddling, but it's not brain surgery. If yours are coming on late, or not at all, they need to be bent more, but only very, very slightly.

    [​IMG]

    This first pic shows the brake light switch, as well as the tab that needs to be bent. There is one on top and one on the bottom. If they are bent too much, then the brake lights will be on all the time. If the tab is too flat, as they are on a brand-new switch, the lights may not come on at all.

    [​IMG]

    This is a pic of the master cylinder pushrod that the switch contacts when assembled. See the flats on the end I was talking about earlier? That's what pushes the tab into the switch, closing the circuit and making the brake lights come on. Hopefully this gives you an idea of what's going on and how to adjust it so it works correctly.
    The disassembly is easy, but critical. There's a clip on the end of the stud that the switch and pushrod mount to, remove the clip and there should be a 1/8" plastic spacer that slips off. Then wiggle the pushrod/switch out towards the end of the stud so it's all flush on the end, then simply push the rear of the switch upwards and take it off. Oh yeah, unplug the switch first, it'll be easier that way. When you reassemble the whole thing, please make SURE the clip is in snug, because if it's not, and it falls out, there's nothing at all to keep the master cylinder pushrod on the brake pedal, and if it fals off, you will have no brakes. Let me know if you need anything else, Jim
    #4
  5. Mach1 Ian

    Mach1 Ian New Member

    Joined:
    Nov 15, 2006
    Messages:
    37
    Likes Received:
    0
    Trophy Points:
    0
    Location:
    United Kingdom
    Thanks for the pictures Jim, they are a great help, my switch isn't held on with a clip but a pin that goes through the lug on the pedal, so no chance of it coming off and no brakes, one question though as the lights don't work till the pedal is pushed really hard, do i bend the tangs to wards the spring or away from it?

    Thanks again
    Ian
    #5
  6. zookeeper

    zookeeper Founding Member

    Joined:
    Aug 25, 2001
    Messages:
    3,169
    Likes Received:
    3
    Trophy Points:
    59
    Location:
    Northern California
    If the brake lights are not coming aren't coming on soon enough (or at all) then you need to bend the tabs upwards as shown in the first photo of the switch, or forwards as mounted in the car so that it contacts the mastercylinder pushrod sooner.
    #6
  7. Mach1 Ian

    Mach1 Ian New Member

    Joined:
    Nov 15, 2006
    Messages:
    37
    Likes Received:
    0
    Trophy Points:
    0
    Location:
    United Kingdom
    Thanks for the help Jim, i will have go at sorting it out, i will let you know how i get on with it.

    Thanks
    Ian
    #7
  8. Mach1 Ian

    Mach1 Ian New Member

    Joined:
    Nov 15, 2006
    Messages:
    37
    Likes Received:
    0
    Trophy Points:
    0
    Location:
    United Kingdom
    Jim you are a real star!!! i followed your instructions and sure enough it worked :nice: now the brake lights come on when i push the pedal down with my finger, rather have them come on sooner than later.
    What are you like at brakes?
    2 years ago i had a SSBC power disc conversion fitted on the front and i have never been really happy with result. The problem is no matter how hard i press the pedal i can't get the front brakes to lock up, it feels as if the pedal will only go down so far, not far enough to bring the brakes on fully, i wouldn't like to think of high speed braking as they are.

    Thanks
    Ian
    #8
  9. zookeeper

    zookeeper Founding Member

    Joined:
    Aug 25, 2001
    Messages:
    3,169
    Likes Received:
    3
    Trophy Points:
    59
    Location:
    Northern California
    Glad to hear you got it fixed, can't have you running around with no brake lights now, can we? As far as the front brakes go, did your kit come with an adjustable proportioning valve? If it did try dialing it to supply more pressure to the front. If it didn't buy one and install it in place of the whatever non-adjustable valve there is in the line now. Typically, the factory one is nothing more than a distribution block anyway, and in my opinion too much pressure is sent to the rear drum brakes. Drums don't need high line pressure since they are "self energizing" but discs do need more. It also sounds like the bore on your master cylinder may be too big. A large bore master cylinder makes for a high effort pedal that doesn't stop the car. If your car is equipped with a large bore master cylinder, like a 1 1/16" bore, try dropping down to a 1" bore or even a 15/16" bore. The small bore will provide an eaiser pedal and greater stopping power, but the pedal may move a fraction of an inch farther. Either way, it's the master cyinder or something related to the master cylinder causing your problems.
    #9
  10. Mach1 Ian

    Mach1 Ian New Member

    Joined:
    Nov 15, 2006
    Messages:
    37
    Likes Received:
    0
    Trophy Points:
    0
    Location:
    United Kingdom
    Thanks again Jim for your help.
    The kit came with a proportioning valve and every thing is fitted as per the instructions, another problem that occurred was the fluid in the new master cylinder was leaking out through the seal on the lid and emptying the rear bowl, so the mechanic drilled a small hole between the 2 bowls and that cured it, but that was a last resort after having 2 replacement master cylinders from SSBC and still doing the same thing, i have just measured the bore of the other 2 MC's the end which fits up to the booster and they are 1 /16" the MC's were part of the conversion kit, a friend of mine came up with the same answer as you have, so it looks like i am on the right track for a solution. Where would i be able to get a 15/16" bore MC? as none of the US suppliers i use do not state bore sizes.
    Thanks again for your help
    Ian
    #10
  11. zookeeper

    zookeeper Founding Member

    Joined:
    Aug 25, 2001
    Messages:
    3,169
    Likes Received:
    3
    Trophy Points:
    59
    Location:
    Northern California
    I can't for sure give you an answer on bore sizes on OEM master cylinders, but I do know that Wilwood has lots of master cylinders with various piston sizes, and I remember measuring one I borrowed from a freind and it was VERY close to a bolt-on. Not only that, but it was only like $50. If I were you, I'd do some checking with Wilwood, tell them what you have and what you want to do and see what they suggest. I know my wife's '69 Corvette has a 1" bore master cylinder with manual discs at all 4 wheels and it stops fine, while my brother's street rod uses the same master cylinder with a power booster and the brakes are much more sensitive. Having said that, if it were me (and it's not) I'd go with a 1" master cylinder.
    #11
  12. Mach1 Ian

    Mach1 Ian New Member

    Joined:
    Nov 15, 2006
    Messages:
    37
    Likes Received:
    0
    Trophy Points:
    0
    Location:
    United Kingdom
    Thanks Jim i will get in touch with Wilwood and see what they come up with.

    Thanks
    Ian
    #12
  13. TOM B

    TOM B New Member

    Joined:
    Nov 15, 2002
    Messages:
    868
    Likes Received:
    0
    Trophy Points:
    0
    Location:
    Harrisburg Pa
    Now that is just exellent help, just dont get any better:nice::nice::nice:
    #13
  14. Axlepressbutton

    Axlepressbutton New Member

    Joined:
    Mar 9, 2014
    Messages:
    1
    Likes Received:
    0
    Trophy Points:
    2
    Brake light issues after installing my disc brake set-up with new master cylinder had me scratching my head for awhile.
    After searching the net I found your solution. A+ explanation. Thank-you!!
    A patient and clear explanation that had my lights working in 5 minutes.
    Star*****


    #14
  15. zookeeper

    zookeeper Founding Member

    Joined:
    Aug 25, 2001
    Messages:
    3,169
    Likes Received:
    3
    Trophy Points:
    59
    Location:
    Northern California
    Glad you could use the info! Also, here's something I found out a while back: my car was originally an automatic-trans car when I posted the info. Since then I converted it to a T5 manual trans and I can assure you, the brake light switch is NOT coming out in a couple minutes! To anyone converting thier car over to manual trans, which requires swapping to a smaller brake pedal, spend the time adjusting the switch BEFORE you put the clutch pedal in place! I took my steering column out to do the swap and can assure you if anything needs to be tweaked our adjusted, removing the column is far easier than trying to work around a clutch, brake and steering column nightmare!
    #15
  16. horse sence

    horse sence Please don't call me Mom SN Certified Technician

    Joined:
    Nov 30, 1999
    Messages:
    3,887
    Showcase:
    164
    Albums:
    5
    Likes Received:
    616
    Trophy Points:
    153
    Location:
    Wile Coyote's stunt double
    Yep there isn't much room to work under there . one more thing i would like to add is if you have the clutch rod disconnected to the pedal be careful ,the helper spring on the clutch pedal will pull the clutch pedal to the floor with a lot of force and can break a finger. And it will also pop up if you pull up on it.
    #16
  17. zookeeper

    zookeeper Founding Member

    Joined:
    Aug 25, 2001
    Messages:
    3,169
    Likes Received:
    3
    Trophy Points:
    59
    Location:
    Northern California
    I fabbed up a hydraulic clutch myself, but yeah, the stockers with the spring can cause some grief. Don't ask me how I found that out...
    #17
  18. horse sence

    horse sence Please don't call me Mom SN Certified Technician

    Joined:
    Nov 30, 1999
    Messages:
    3,887
    Showcase:
    164
    Albums:
    5
    Likes Received:
    616
    Trophy Points:
    153
    Location:
    Wile Coyote's stunt double
    Probably the very same way i did.
    #18

Share This Page