Brake Light Problem

[NickJ]

Hi, I have a problem with the brake lights coming on as soon as the ignition is switched on :?:
Any advice gratefully accepted, Cheers Nick.

 

[NickJ]

I've just checked the 4 wires that connect to the master cylinder and they are all live, is that right :?
The engine came out recently to access the fuel tank and I noticed the lights on when I got it home.
Any ideas please.

 

[faux]

I think there should be:

2 Switches =
2 x black - Live,
2 x Red - Only live when there is an issue (these feed to the dash as a warning light)
2 x Black and Red - only live when engaged

Or

2 Switches =
2 x black - Live,
2 x Black and Red - only live when engaged

Could be a faulty brake switch on the MC - have a look on here for wiring diagrams:
http://www.vintagebus.com/" onclick="window.open(this.href);return false;

 

[ground hugger]

One wire on each pressure switch should be live,when you press the brake the switch makes contact making the other two wires live thus turning the lights on.So two wires should be live with ignition on.Sound like the master cylinder is holding pressure some how or both switches are shot

 

[NickJ]

Thanks for the link and info but when I checked the connections to the MC I took the plugs off and checked them with a 12v tester and all four were live disconnected from the MC which makes me think it's not the MC (this was replaced for the MOT in March although the old switches were refitted)
A bit more investigation needed I think, any more ideas :? Cheers Nick.

 

[currylager]

Its probably one of those switches , easy way to tell is leave ign on, unplug both switches and brake lts should be out , plug in each switch at a time, if brk lights come one with one switch connected and no pedal , you know its that one thats faulty

 

[NickJ]

Thanks once again, I'll check in the morning and let you know how I get on. Cheers Nick.

 

[NickJ]

Well i did the unplug test this morning, took both plugs off the MC with the ignition on and the brake lights stayed on :x

 

[faux]

A case of follow the wires! :|

 

[currylager]

Are there plugs on the MC switches? (mine are just spade connectors) If so it could be possible that the wiring has shorted out in the back of one of the plugs somewhere?. I had the same fault with mine but one of the switches was faulty, so i just disconnected one of them and now my brake lights are operated by one switch . Have you changed the rear light bulbs recently?, it is possible that a poorly fitted bulb can short the brake light and tail light contact and operate the brake lights via the tail light circuit if it is switched on, just a thought :roll:

 

[NickJ]

Cheers again fellas,
Jon that's what I was thinking but as it looks a bit like a pigs guts under the dash I was hoping for an easier answer :lol: but I suppose that was wishfull thinking.
Currylager yes there are plugs and I hadn't thought about a problem with the plug itself I'll check them out first next time I get on it.
Thanks Nick.

 

[NickJ]

Well I finally got to the bottom of the problem after checking and rechecking, I eventually found that when a new front panel was welded on several owners ago whoever did it didn't take enough care keeping the wiring out of the way :roll: and this was melted so that all the wires were live together. What I don't really understand is why it has taken several years for this to show itself but at least the brake lights now only come on when the pedal is pressed