XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

Brake lights on permanently - switch?

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Old 07-13-2020 | 03:25 PM
Asdrewq's Avatar
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Default Brake lights on permanently - switch?

Hi all,
I bled the front brakes on my 1989 ABS-equipped car recently, & my brake lights are now on all the time with the ignition.
It looks like all the pushing the pedal to the floor has broken the switch.
Does anyone know where it is located - is it up by the pedal somewhere or on the master cylinder?
 
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Old 07-14-2020 | 07:56 AM
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I assume the 89 is teh same as my 85??

Inside the car, look up from the pedal pad (the bit you put your foot on), and you will see it.

The arm may simply be stuck.

Easy to get to, NOT. About as bad as both #1 spark plugs.

Lay the seat flat, head under the dash, feet near the rear window, and go for it, is all I can say.
 
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Old 07-14-2020 | 02:03 PM
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Hi Asdrewq

You'd have a job to break the Brake Switch on an 89 because as you push the Pedal down, the Brake Light Switch is fixed to the inside of the Firewall underneath the Pedal Box, so when you push the Pedal down you leave the Brake Switch behind where it is, instead of Crushing on it

As all that really happens as you push the Pedal down, is that it gives the Switch in its holder enough room to spring out, so in other words the Brake Lights come on when the Pedal Arm loses Contact with the Switch (rather than making contact with the Switch) which is a different setup to that on the earlier Cars

You've probably jammed a wire or something like that, very easy to get to 'NOT' unless you can stand on your head!

Just don't go breaking the Brake Switch as they are 'Megabucks'!
 
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Old 07-18-2020 | 07:55 AM
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My brake pedal doesn't quite return to the full "off" position when you release it...it stays 2-3 mm low and it's just enough to make the brake lights come on. I have to remember to hook the pedal up with my right foot when pulling away, as I have not found an adjustment that will correct it. Perhaps a master cylinder rebuild? Could that be what is happening in your car, Asdrewq? Ie., the switch is fine.

Incidentally, I believe such a switch is referred to as "push to break" the circuit as opposed to the more common "push to make".
 

Last edited by Mkii250; 07-18-2020 at 07:58 AM. Reason: pedantry
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Old 07-22-2020 | 05:51 AM
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Originally Posted by Mkii250
My brake pedal doesn't quite return to the full "off" position when you release it...it stays 2-3 mm low and it's just enough to make the brake lights come on. I have to remember to hook the pedal up with my right foot when pulling away, as I have not found an adjustment that will correct it. Perhaps a master cylinder rebuild? Could that be what is happening in your car, Asdrewq? Ie., the switch is fine.

Incidentally, I believe such a switch is referred to as "push to break" the circuit as opposed to the more common "push to make".
BINGO - Thanks for that - It would never have occurred to me.
The pedal was stuck slightly down.
I pulled it back up with my hand & it 'thudded' up maybe another 1cm or so - it felt like it was overcoming some sort of resistance.

I then applied it, when pushing hard down & hear the pump running (I think my accumulator is dead so pump runs every time you touch the brake pedal) I felt an identical sensation in the pedal (a pressurised 'thunk') while the pedal pressure was being applied.

I released it, it got stuck again. Pulled it up, reapplied pressure.
I did that maybe 5 times & now it feels better & returns fully & the rear brake lights go off.

No idea what's going on but I don't understand this ABS system at all & really dislike it. It seems completely un-intuitive & really untrustworthy.
I need to change the accumulator ball at some point & bleed through the rear brakes - just hoping all the weirdness disappears after that.
 
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