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Handbrake warning light on 1980 Triumph Tr7 coupe Instrument Cluster


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Was wondering if anyone could assist me in fault finding my inoperative Handbrake warning light.

Initially it came on when the handbrake was applied 50% of the time but now it doesn’t work at all.

I have removed the centre storage box and accessed the brake switch which appears to make contact with the handbrake when it is applied.

However when I check the wire to the switch there appears to be no voltage there at all.

I assume there should be, and when the handbrake is applied it forms the circuit and illuminates the light on the instrument panel.

I have tried to follow the cable (Black/white) back to the dashboard but it is beneath the carpet and I lose it, so I have no idea where it goes.

Any idea what to do next?

Cheers

John.

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It may just be an earth switch, does the switch actually provide continuity through when operated?

Stuart.

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If you haven't got a circuit diagram it is here - page 5:

https://drive.google.com/file/d/0B0OCjgNgn85aOEdlYWp6dnFfc2s/view

As Stewart says, the switch just  provides an earth for the warning lamp.

It may be that the warning lamp in the instrument console may be blown or not making proper contact. If the other lamps are working there should be power to the bulb.  

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Thanks for the info, i suppose it could be the bulb, but i’ll check the switch again first for continuity & report back.

Cheers
 

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Quick checks - If you meter on the black/white wire with ignition on you should see 12v more-or-less if the bulb is good and making contact. The meter resistance is much greater than the bulb resistance so there will be next-to-no volts drop and the bulb will not light.

Earthing the wire directly should light the bulb.

Edited by RobH
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  • 1 month later...

 

Hi

I have finally changed the warning light bulb,  but it still does not work when the handbrake it applied.

(I managed to change a couple of the dash bulbs at the same time so it wasn't a waste of time)

Looking at the wiring diagram there should be a connection from black/purple to a black/white.

I have tried to trace back the black/purple from the handbrake switch but the wire seems to head towards the rear of the car beneath the carpet at the side of the transmission tunnel.

Can't find it anywhere in the back of the car.

Could it be threaded through the floor and running externally?

I will persevere,  as this is now the only snag left to rectify.

 

Cheers

John

 

 

IMG_8886.jpg

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Wire runs back to behind the trim behind the seats and then runs across to the passenger side before running forward along the side of the footwell. I am not sure how it finally gets to the instrument cluster however.

See the attached photo which shows the wiring in this area.

Cheers

Howard

IMG_3740.JPG

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Hi,

Well I fixed it!

Removed centre storeage consol, & back panel to locate the wire, found it, followed it down the passenger side beneath the carpet and it came into a multi plug where it joins onto the black/white.

Nothing found there.

Had a look under the centre grill cover on top of the dashboard - loads of wires & plugs.

Pulled them all out one by one and found one end of a multi plug with a black/white & green/white.

Fiddled about & found the other end - put them back together and the light now comes on when handbrake is applied.

How on earth did they come apart?

A good job done as I managed to replace 3 dash bulbs and the clock I bought about 2 years ago, and never got round to fitting.

Thanks to those that offered the advice - much appreciated.

Regards

John

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