MOT Cancelled

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Royalratch
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Fri Dec 04, 2009 10:02 am

Because my brake lights don't work...

I'm having a nightmare with my electrics at the mo :-x

There is voltage at the brake switch plug but just under 12V (11.7V). A test with a 12V bulb yields no light. Switch seems to work okay.

I did my own 'MOT' the night before to ensure a pass and this is the only thing that could cause a fail.
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Royalratch
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Fri Dec 04, 2009 2:50 pm

:D
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Speedtouch
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Fri Dec 04, 2009 2:58 pm

Blown fuse or another loose connector?

The switch itself can be tested by removing the connecting cables and using a multimeter on continuity buzzer mode or low resistance across the switch contacts. Pressing the brake pedal should obviously close the switch, resulting in either low resistance or a buzz.

Main +ve feed to the switch should be capable of lighting a test lamp.
///M aurice
ECU Upgrade EPROM Chips, £40 posted within the UK. Note these are not Zone chips.
viewtopic.php?f=6&t=279421
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Royalratch
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Fri Dec 04, 2009 3:06 pm

I was going to check the switch for continuity next but still the issue of low voltage...
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Speedtouch
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Fri Dec 04, 2009 3:17 pm

According to my Haynes manual, Fuse 41 is the one to check. You could pull the fuse out and test the voltage from its socket.

You mentioned that your battery is a bit duff: if that's the case, it's possible that it doesn't have enough voltage output to operate the brake lights test unit in the boot. Do they operate with the engine running (battery being charged), or was the test carried out with just ignition on?
///M aurice
ECU Upgrade EPROM Chips, £40 posted within the UK. Note these are not Zone chips.
viewtopic.php?f=6&t=279421
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Royalratch
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Fri Dec 04, 2009 3:22 pm

Battery is brand new and lives on a CTEK conditioner and is tip top.

Fuses are all in tact.

They don't operate in any of the situations you suggested.
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Speedtouch
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Fri Dec 04, 2009 3:38 pm

In that case, it's probably a loose or corroded/dirty connector somewhere; did you clean the C101 terminals when you discovered the top was loose?
///M aurice
ECU Upgrade EPROM Chips, £40 posted within the UK. Note these are not Zone chips.
viewtopic.php?f=6&t=279421
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Royalratch
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Fri Dec 04, 2009 4:00 pm

No - but they looked perfect and the rest of the rear lights work fine.

Must be the switch and of course I don't have a spare!
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davse30
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Fri Dec 04, 2009 4:22 pm

pull the wires off the brake light switch and short them together with a piece of wire ,if your brake lights come on its your switch if not leave the wire in and start testing from the rear lights backwards till you find the fault :wink:
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Royalratch
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Fri Dec 04, 2009 4:23 pm

Will do - cheers chaps!
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