MOT Electrical problems

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salty_monk
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MOT Electrical problems

Post by salty_monk »

Ahh failed MOT :cry:

Luckily the intermittent horn worked ok but the brake lights refuse to light!

Can't see it's an earth problem (I'm still positive earth) as all the other lights work ok & I believ are al earthed at the same point at the rear,

Have cleaned up all the green contact on top of fuse box, checked bulbs etc. Have also cleaned up the contacts on the back of the horn itself & the push. Will now get the meter out!!

Does anyone know where the brake light switch is? I no a green wire goes to it & a green purple comes out the other side but where is it? Presume it's down by the pedal, do you access through the reservoir plate or from underneath??

Cheers! :)
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aupickup
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Post by aupickup »

hi
sorry to hear about the fail

brake switch is in the engine bay, on the floor, it is situated on the offside just in front of the radiator panel

should not make any difference whether neg or pos earth, as neg all earth is neg and pos all earth is pos.

as you have no brake lights at all could be the switch, an easy job to do

can not help on welding though, i thought wax oil and cavity wax was less flammable with age, may be wrong
au
aupickup
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Post by aupickup »

sorry but why should an intermittent horn be lucky for the mot, it should work all the time, also as a matter of point, it is best to check all lights at least before the mot, but then serviced at mentioned times, lights should be a routine check for you.
salty_monk
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Post by salty_monk »

I knew it was going to fail on some welding so just took it in for a fail sheet! Not worth wasting my time beforehand!

Thanks for showing me where the brake switch was, obvious when you know!! :) I've shorted the wires across & the lights work so I guess that's the problem. Will get a new one sent through on Monday. Presume that fitting it doesn't require a re-bleed of the brakes or anything?? Is it just a standard thread? Whip one off & screw the new one in it's place??

The horn works 98% of the time, think it was just dirty contacts as I've been playing with it this morning & it's working fine now!!
Unfortunately I have 4 vehicles to keep on the road & am in process of starting a new company, have just moved house & have spent 2 months of the last 6 in China, unfortunately the moggie's lost out a bit on anything but essentials!! :D
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aupickup
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Post by aupickup »

i know i have 3 commercial moggies.

i think if you raise the car at the front so the switch is at the highest point, and put some brake fluid in the switch it can be changed without bleeding the brakes
Chris Morley
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Post by Chris Morley »

There should be no need for a bleed just to replace the brake / stop switch. Undo the old one and quickly replace it with the new one. I put some brake fluid into the new switch held upside down, then tipped into position at the last second - to avoid an air bubble forming. Note you may need to brace the brake pipes when you're trying to undo the old stop switch (they can buckle if the switch is seized into the union). I used a piece of soft wood jammed between the 3-way union and the front grille). :wink:

My horn also didn't work when the wheels were dead straight - I guess the sliding / slip connection had worn out? When I tried to pull off the horn switch (late 1098cc) it disintegrated..... :x
Chris
-------------
1969 2-Door daily driver
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