93 defender intermittent brake light issue.

Peat76 · Nov 24, 2018

My defender has finally had its chassis blasted, repaired and stone chipped but on driving it back I noticed both brake lights weren’t working .
I’ve replaced the fuse and both bulbs and out of about 10 quite hard pedal presses the brake lights came on twice.
The rear lights work fine.
Am I looking at a wiring issue from the sand blasting or would the rear lights also be out if there was a wiring issue ?

Hicap phill · Nov 24, 2018

Sticky brake pedal switch?

Flossie · Nov 24, 2018

Just link the two wires together going to the brake switch(rear of master cylinder under the bonnet). If they work fine then the switch may have sand in it which may be possible to tap and blow out? Otherwise replace it.
If you've blasted the vehicle assembled I suspect you're going to have more problems arising.

Flossie · Nov 24, 2018

What grit was used?

Peat76 · Nov 25, 2018

Flossie said:
Just link the two wires together going to the brake switch(rear of master cylinder under the bonnet). If they work fine then the switch may have sand in it which may be possible to tap and blow out? Otherwise replace it.
If you've blasted the vehicle assembled I suspect you're going to have more problems arising.

Thanks. Just watched a few videos on brake switches and they are all dealing with a thing behind the brake pedal. Is that the same thing that’s in the engine bay or is there two things I need to check ?

Yeah it was done assembled. At this point in time I couldn’t afford a chassis replacement so just had to get work done to get the major stuff sorted so I could safely use the defender.

I’ve had to unstick one door lock that was jammed solid so far.

Peat76 · Nov 25, 2018

Flossie said:
What grit was used?

Not sure. There is a lot of tiny black balls inside the defender. Like microscopic ball bearings .

Peat76 · Nov 25, 2018

Just been to have a look.

Is the brake switch that thing in the middle of the picture that I've sprayed wd40 on?

If so, I take it I have to loosen the nut at the bottom, the switch comes out then I can spray wd40 on the push bit and my brakes work perfectly again ? ......

Hicap phill · Nov 25, 2018

Short the 2 cables out on that switch first. This will prove if switch is faulty.

Flossie · Nov 25, 2018

Peat76 said:
Not sure. There is a lot of tiny black balls inside the defender. Like microscopic ball bearings .

Sounds like J blast. That stuff will break down over time. If they had used metallic grit you'd have rust breaking out everywhere it collected and it collects everywhere.
Wd40 won't fix a grit filled switch. If linking the wires confirms a sticky switch, remove it (make a note of how many turns it's set at ) and tap it/work the plunger until it's all good again or replace it.

Peat76 · Nov 25, 2018

Cheers. Well I went ahead and had a go. Took ages to get the bl00dy wires apart. But tested the wires with a multimeter and got a tone. So that’s good (I’m guessing ) .
I don’t really understand what is meant by linking the wires :/.
Unfortunately I had a go at removing the switch before reading your post so didn’t make a note of how many turns it was. Doh.
Plunger seems to be moving perfectly fine but gave it a clean and pushes but when I went to put it back in I couldn’t do it.
I would get the switch in position turn it a full 360 maybe a few times I think. It would feel solid in position so then I would tighten the nut but when that got tight the whole switch would pop out. I tried 4 times and it happened every time.
I’m guessing I’m doing something wrong like

Edit: just watch Britannicas video again and realised he tone tested the switches wires to make sure the switch was working .. flipping heck. I tone tested the other side of the wires thinking if I got a tone that meant there wasn’t a problem with the wiring to the lights.

Flossie · Nov 25, 2018

The thread on the switch is probably knacked, I think it's only plastic?
Anyhoo, the two wires going TO the switch, disconnect them(which you've done) join them together and if all is good with the wiring, the brake lights will light up, ign on.
The two short wires FROM the switch are what you need to test for switch operation.

Peat76 · Nov 25, 2018

Thanks. Yeah I’m gonna try pick up a new switch tomorrow might as well change it anyway.

How many full rotations does it normally take to screw in the switch? I’m a bit paranoid i over tightened this one and striped the plastic thread.

Flossie · Nov 25, 2018

Dunno.
Just screw it in until the brake lights come on and then back it off until they just go out plus another 1/2 turn. Some fine tuning may be needed.

Peat76 · Dec 1, 2018

Brake light switch replacement fixed my issue. I couldn’t get the old nut to fit over the new switch so left it off. But all is working so that will do

93 defender intermittent brake light issue.

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