Instrument Lighting

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Kittyhawk
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Instrument Lighting

Post by Kittyhawk »

1968 1000 Traveller. I have just replaced a blown instrument light bulb. On replacing the speedo in the panel, the fuel gauge reads empty (with a full tank). If I remove the speedo again, the gauge reads normally and in addition, the instrument lights come on despite the light switch being in the off position. Anyone have any thoughts please?
les
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Re: Instrument Lighting

Post by les »

It sounds like the gauge terminals are hitting something as the speedo is positioned, push any nearby wires away from where the back of the speedo sits. Check for loose wires or broken insulation. Sorry it’s a guessing game, not being there !

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geoberni
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Re: Instrument Lighting

Post by geoberni »

Crystal Ball time, with a fair bit of logical thought process.. :wink:

On refitting the Speedo, you've clearly disturbing, i.e., breaking a connection at the Voltage Stabiliser, that's why the Fuel Gauge isn't working.
However, Instrument Lights coming on, well that connection to the Voltage Stabiliser is apparently shorting to the Instrument Lights. :-?

So you'll just have to conduct a thorough examination of all the wiring and connections in that area; you'll find something eventually.

Only you know the condition of your car's wiring, the older and dilapidated it is, the greater the chance of these things happening.
Assuming it's the original loom, it's 57 years old, long beyond it's intended lifespan.
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Kittyhawk
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Re: Instrument Lighting

Post by Kittyhawk »

I have checked for anything which may be contacting the back of the gauge and giving a spurious earth. My understanding is that the speedo needs to get it's earth from contact with the dash when it is pushed into place, but everything works as it should when the speedo is out of the dash, so it must be getting an earth some other way?
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Re: Instrument Lighting

Post by Sleeper »

Do any of your speedo lamps ( turn,ignition , oil ,battery etc. ) have fittings with earth attached?

John ;-)
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Re: Instrument Lighting

Post by Kittyhawk »

The oil pressure lamp sender earths through the engine block.
All the lamps including the two speedo illumination lamps work with the speedo out of the dash.
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Re: Instrument Lighting

Post by Sleeper »

Speedo drive inner?

John ;-)
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Re: Instrument Lighting

Post by Kittyhawk »

I disconnected the Speedo drive. Everything still works. Pulled everything electrical out of the back of the Speedo, just leaving the B & I connections to the voltage stabiliser and the green/black from the tank sender. Fuel gauge still works. Shorting the Speedo body to the panel or the two lugs for the Speedo retaining bolts, fuel gauge stops working.
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Re: Instrument Lighting

Post by Sleeper »

Looks like you're just left with the voltage stabiliser, which should need an earth to work? Next B and I ?

John ;-)
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Re: Instrument Lighting

Post by Sleeper »

Looks like you're just left with the voltage stabiliser, which should need an earth to work? Next B and I ?

John ;-)
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Re: Instrument Lighting

Post by Kittyhawk »

I can’t see how it is the voltage stabiliser, as the gauge works correctly when the Speedo is out of the panel.
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Re: Instrument Lighting

Post by svenedin »

The instrument lights on the speedo have a live feed via the little switch under the dash and the earth is provided by the speedo fixings. If the panel lights are still on with the speedo out of the dash and the panel light switch in the off position then there is obviously something amiss. The little switch under the dash has screw terminals that just make contact with bare wire. Has a wire come adrift? The feed to the switch is a red wire and the output to the panel lights is a white/red wire.

Stephen
Last edited by svenedin on Tue Jul 01, 2025 9:37 pm, edited 1 time in total.
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Stephen
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Re: Instrument Lighting

Post by Sleeper »

Kittyhawk wrote: Tue Jul 01, 2025 6:19 pm I can’t see how it is the voltage stabiliser, as the gauge works correctly when the Speedo is out of the panel.
Looks like we're searching for a stray earth on the speedo when not in the dash..... By a process of elimination,you only have the B and I wires left ?

John ;-)
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Re: Instrument Lighting

Post by Kittyhawk »

The instrument lights are now behaving normally.
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