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Stop lights


dougbgt6
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Friday, failed the MOT. No stop lights. They were working when I checked on Thursday. Bugger!

 

Bulbs OK, earths OK, no current drain when peddle depressed. Brake light switch!

 

Where is it? Never seen it these 40 years! On the brake pedal, fool!

 

Head in footwell, arms at full stretch, got a finger on it. Ping! 6 pieces on the floor.

 

Today, new switch. What a pig of a job! Would be easy with two extra joints in my forearms. Got it on!  And, the MOT is mine!

 

Just thought you should know.

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many or the switches are a cheap plastic thing, if it replaces a orig metal one there is a basic  design fault ,  the brake pedal uses the switch as a back stop, 

on the old switch it works ok but with the cheapo the nut needs to be long enough that the fixing nut stops the pedal return not the switch plunger

or a quick release of the pedal will hammer the plunger and the clip in back of the switch ends up on the floor

 

we used these switches on trucks for years but had a long sleeve nut to  act as the stop...

 

Pete

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As far as I could see, (by the light of the ignition courtesy bulb! :blink: ) the nut that holds the switch in place is massive and the plastic thread does not protrude through it. So with the pedal at rest the plastic plunger is pressed flat to the top of the nut and the pedal rests on the nut rather than the plastic threaded  outer sheath. Also the plastic thread appears to be tapered so it gets harder and harder to do up the nut. A safety feature so that the nut won't come undone? Cunning, these Triumph design chaps!

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  • 1 year later...

Hi Everyone. I am having trouble with the brake lights on a 1972 Mk IV Spitfire. Putting it back on the road after 20 years, found the brake light switch in bits on the floor. Got a new one..... exploded into bits, reassembled and now working but no power to lights. Switch is passing power but nothing at the light dimming relay. Connected switch directly to the lights with a fly lead and works fine!! I notice on the wiring diagram (Haynes and BL workshop) a circle with a cross between the switch and dimmer relay. What is this, where is it, and could this be the problem!? Failing that any suggestions other than a break in the wiring loom? Thanks

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Bw,

I thought - in fact I'm sure - that a circle with a cross on it is an alternative symbol for a light bulb in a wiring diagram.    But there is no sense in that meaning for the crossed circle where you, and I, find it.    Worse, in diagrams for later Spitfires in the Haynes manual there are circles that are half black, half white, and also quartered black and white!    None of these are light bulbs as the same diagrams use the other symbol for those, a circle with a twist across it, meaning the filament.

 

Could it be that these signify connectors?   But the diagrams omit those everywhere else.

John

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In wiring diagrams generally, a circle with a cross in it is an incandescent bulb. But I've never seen a warning light on Triumphs that says "your brake lights are on". Otherwise a junction connector? I would also recommend you ditch the night dimmer relay. Our lights are dim enough already!

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Hi everyone. Thanks for the advice. I will ditch the dimmer but the problem still remains that there is no power from the (working) brake light switch to the spade connector at the dimmer relay. If the circle and cross symbol on the circuit diagram is a connector I can't see it - any ideas where it could be - and I don't want to strip out the dashboard/wiring loom at this point. Perhaps a single wire run from the switch to the lights might be an alternative. Not original but it would get me through an MOT!

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Well done Doug. There is a multiway block connector behind the glove box. Every wire on the circuit diagram with the circle/cross symbol runs through it including a black which is not shown on the diagram. If this is new information (!!!) after 40 years, post it far and wide. The upshot is that there appears to be a break in the green/purple lead somewhere in the loom between the connector block and the brake switch spade connector. Looks like a case for two scotch locks and a new length of wire. Thanks to all for your help. Might have to revive this thread in another 6 months to keep the record going!!

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Never heard of Scotch locks. I have a crimping kit (Pete, insert hair joke here)

 

There was a guy on here a while ago who had found a company making the right colour wires, green/purple, green/red etc.  By all means use what you've got to hand to get the MOT but worth while getting the right colour wire and replacing later on.

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I have a crimping kit too... somewhere!! Thought as a last try that I would take off the spade connector from the switch and test the circuit through the bare wire just in case there is a dry joint in the connector etc.

I also found this on ebay...

http://m.ebay.co.uk/itm/152575984601?_trkparms=pageci%3A64df7afe-57ee-11e7-baa7-74dbd18006c2%7Cparentrq%3Ad4141ad115c0ab4d6d54310dffff945a%7Ciid%3A10&_mwBanner=1

This listing has most of the colours of cable that we might need. Currently £3.50 per 5mtrs. I have spade connectors somewhere from the body off restoration 30 years ago but not the memory to remember where they are!!

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Ok Chaps (and any Chapesses who are reading!). Finally identified the problem as a faulty joint at the spade connector out of the brake light switch. Fitted a new one and it finally works. Now on to replacing the glove box etc. Thanks for all your advice and input. Wait for the next posting and cries for help on another thread.

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Just a final mention for anyone picking up this thread in the future. The problem was that the insulation hadn't been stripped back far enough before fitting the spade connector which pushes onto the switch terminal. There was a microscopic amount of solder in contact with the copper wire and the spade, so when the switch fell apart the simple act of pulling the spade connector off the switch terminal pulled the copper wire away from the solder, but still left the insulation clamped within the spade. Hence no circuit but visually perfect. Only the cry of "well it worked with the old switch perfectly!!!" This could happen with any lucar type spade connector and a simple replacement is the answer. I nearly ended up doing a full rewire!

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