XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

Brake light switch

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Old Dec 11, 2021 | 06:45 AM
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Default Brake light switch

Has anyone ever fitted a hydrolic switch for the brake lights, what would be the best place for the new switch, mine comes on and then turns off the further the peddle goes down
 
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Old Dec 11, 2021 | 08:05 AM
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I took my brake light switch apart this week, cleaned the contacts, used some dielectric grease, and reassembled it. Works fine. The bottom plastic plate is just crimped on. I uncrimped it with a screwdriver, and pried out the plate. Very simple inside. Two copper pads on the plastic plate, and a lightly spring loaded contact plate in the upper half that moves with the lever arm Should be good for another 100,000 miles
 
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Old Dec 11, 2021 | 08:49 AM
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Originally Posted by rgp
Has anyone ever fitted a hydrolic switch for the brake lights, what would be the best place for the new switch, mine comes on and then turns off the further the peddle goes down
Not aware of anyone doing so, no. Sounds like a cure looking for disease.

The hydraulic switches, common until the mid-60s or so, were notoriously problematic. Mechanical switches were the improvement!

Cheers
DD
 
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Old Dec 11, 2021 | 09:05 AM
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Originally Posted by jal1234
I took my brake light switch apart this week, cleaned the contacts, used some dielectric grease, and reassembled it. Works fine. The bottom plastic plate is just crimped on. I uncrimped it with a screwdriver, and pried out the plate. Very simple inside. Two copper pads on the plastic plate, and a lightly spring loaded contact plate in the upper half that moves with the lever arm Should be good for another 100,000 miles
I will do that now. Thanks
 
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Old Dec 11, 2021 | 01:56 PM
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Looking at the internals of the switch it appears that
​​​​​​ If the pedal goes beyond a certain polnt the light connnectors will switch off. I will swap for hydrolic I think

 

Last edited by rgp; Dec 11, 2021 at 02:04 PM.
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Old Dec 11, 2021 | 02:22 PM
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Originally Posted by rgp
Looking at the internals of the switch it appears that
​​​​​​ If the pedal goes beyond a certain polnt the light connnectors will switch off. I will swap for hydrolic I think
You have to adjust the switch in its mount, until it makes contact withva slight movement of the brake pedal. There should also be an overtravel bracket to keep the arm of the switch from going too far. Once adjusted properly, you shouldn't have an issue.
 
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Old Dec 11, 2021 | 02:49 PM
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Originally Posted by jal1234
You have to adjust the switch in its mount, until it makes contact withva slight movement of the brake pedal. There should also be an overtravel bracket to keep the arm of the switch from going too far. Once adjusted properly, you shouldn't have an issue.
I think I must have overlooked the stop on the switch, I will take the steering wheel off tomorrow and have a proper look
 
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Old Dec 12, 2021 | 02:56 AM
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One more question, what is supposed to stop the travel of the switch actuating arm?
as the problem I'me having is ir goes straight down which is taking the contacts past their point of contact
 
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Old Dec 12, 2021 | 01:37 PM
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Here's a photo. You can see the straight arm of the switch resting on the brake pedal lever. Almost in the middle of the photo there is a 90° arm that limits the travel of the straight switch arm when the pedal is depressed. I can't find a part number in the parts manuals for it.


 
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Old Dec 12, 2021 | 02:15 PM
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Originally Posted by jal1234
Here's a photo. You can see the straight arm of the switch resting on the brake pedal lever. Almost in the middle of the photo there is a 90° arm that limits the travel of the straight switch arm when the pedal is depressed. I can't find a part number in the parts manuals for it.
That's fantastic. I am missing that part and it's not anywhere on the car floor. Thanks for your input.
 
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Old Dec 12, 2021 | 02:42 PM
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Possibly C43829 as seen in he illustration below?



Cheers
DD
 
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Old Dec 12, 2021 | 04:10 PM
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Originally Posted by Doug
Possibly C43829 as seen in he illustration below?



Cheers
DD
Doug that's the tapped plate the fixing bolt goes in. It doesn't appear to be listed anywhere.
 
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Old Dec 12, 2021 | 04:52 PM
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Should be easy to fabricate out of some sheet metal. The picture is from my 85, but I checked an 87, and it's identical.
 
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Old Dec 12, 2021 | 06:01 PM
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As mentioned, the hydraulic switches were used on E Types, Mark 2's etc in the 60's. Problematic then, and moreso today as the replacement switches are of inferior quality to the originals. I've also heard of more than one switch coming apart resulting in the loss of all brakes.

Many of the E Type owners convert to mechanical switches to avoid the problems of brake lights coming on late, or not at all. I'd go with an adjustable mechanical switch rather than hydraulic.
 
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