Magnolia faced Smiths Temperature gauge

[gtt1951]

Having been to last weekend's autojumble at Beaulieu, I returned with a number of items. One of these was a Smiths temperature gauge in a face colour that goes better with my speedometer (rather than the black I have currently fitted).
Things I didn't notice prior to purchase - the "rest" position, for the pointer, is at Max. The serial numbers etc. contain the digit string 24V.[frame][/frame]
The "serial number" is TE 2503/00 24V.
I wired it up on the bench (dining room table), with a spare sender, 12V Meccano variable output controller and the sender suspended in a mug of hot water (from the kettle).
The Gauge ran down to the small double-dot between "20" and "80". The lighting for the gauge would come from a surrounding light-source (not a bulb in the back), like the light source for the "Gold" dashboard Series 2 Oil Pressure Gauge (which I have also obtained from elsewhere).
Questions:-
(1) Is this really a 24V supply gauge?
(2) What would it have come out of?
Thanks in advance for any help and suggestions,
George.

[MarkyB]

Did you try it in cold water?
24 volt could be lorry or coach.

[gtt1951]

Hello MarkyB, that was remise of me - no I didn't and I should have had. I did, accidentally, wire it up incorrectly, to start, and fed "battery" through the gauge, without the sender takeoff being connected. In this mode it went over to slightly less than Zero.
I'll try the set-up without any water dip (room temperature), then cold water.
Ta, George.

[bmcecosse]

The Meccano controller would be pushing out ~ 18 volts with no 'load' to haul it down.......

[gtt1951]

Hello BMC, checking the controlled DC output with a moving-coil voltmeter, I get 14V on max setting and 12V one notch down.
Having checked the gauge and sender in cold water and at "room temp", the reading displayed is between the 80 and the thin red line.
This looks like I would need a different type of sender (reverse action ?).
Also looks like I wasted my money, just for the sake of getting an intrument with a "matching" face colour.
Hate to give up though. George.

[mike.perry]

Smiths do a complete set of magnolia faced instruments[frame][/frame]