Extra Instruments

[MorrisTenFour]

Any advice please on where best to tap into a power source for the instrument back lighting on my Smiths oil and water gauges without dismantling half the dashboard ? !
Obvious place would seem to be the little instrument light switch under the dash, but even this looks extremely difficult to get to.
Any tips most gratefully received.

Paul Harris.

[svenedin]

The issue is that you only want the backlighting to come on for your extra instruments when the sidelights and or headlights are switched on.

The little instrument panel switch is quite good place to take power from because your extra instrument backlighting will turn off with that switch as well as the speedo panel lights. However, the connections to that little switch are the rather primitive screw terminals. An alternative is to take your power from headlight/sidelight switch. You can use a terminal that becomes live when the switch is on. To access this you should only need to pull the speedo out forwards. To gain extra room, remove the speedo cable from the back of the speedo. Be aware that certain cables are permanently live behind the speedo so disconnect the battery to prevent accidental short circuits.

Stephen

[Bill_qaz]

Pull speedo forward by just slacken not removing screw either side. Then use one of the existing speedo illumination light to T into the wire. You made need to earth your gauges depending on mounting.

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[MorrisTenFour]

Thanks for your help folks. Very grateful.
I will take a look behind the speedo and see what I can do.

[geoberni]

Such questions are always given an added difficulty level because we don't know what changes have been undertaken by past owners.

Om a standard car, solid Red, with no Trace Colour was used for the feed to the sidelights and the Speedo light switch.
The problem is that solid Red is often used on aftermarket extras, Radio etc

But if you can look up under the dash and see some solid Red, it's a good choice to tap into.

[Bill_qaz]

Such questions are always given an added difficulty level because we don't know what changes have been undertaken by past owners.

Om a standard car, solid Red, with no Trace Colour was used for the feed to the sidelights and the Speedo light switch.
The problem is that solid Red is often used on aftermarket extras, Radio etc

But if you can look up under the dash and see some solid Red, it's a good choice to tap into.

Thats why I suggested T into the existing wire to the original instrument illumination rather than guessing a wire.

[Mervin]

I think that the illumination for my gauges was taken from the main lights switch. Access was made through the right side glove box aperture.
Bear in mind that an electric Smiths water temp. gauge requires a regulated 10v supply.

[Bill_qaz]

I think that the illumination for my gauges was taken from the main lights switch. Access was made through the right side glove box aperture.
Bear in mind that an electric Smiths water temp. gauge requires a regulated 10v supply.

The one I showed is a capillary so illumination is only electric but good point as OP didn't say which type is being fitted.

[Mervin]

Yes Bill, I probably should have added, depending on which type Paul has fitted/is fitting.