FYI,

Having seen various questions put up about malfunctioning gauges, here is some info on the "Dashboard Voltage Stabiliser device".

It is a small metal cannister that is earthed & hangs (the right way up (see the direction markings on the top of the can)) on the back of the FUEL GAUGE bracket

Its job is to take the 12 to 15 Volts in, (as the engine revs up) & always send out a constant 10V to the very, very voltage sensitive FUEL & TEMP gauges.

If the device fails you will either get NO readings on these gauges or BOTH will read very HIGH  &/or WOBBLE (& you will wonder why you havn't actualy boiled over yet).     Put your volt meter across the output (feed to gauge) & a good earth. Start engine.....  A STEADY 10V ?    If not, replace the device.

The Smiths part number is BR 1308/00.   They were also used on a variety of old vehicles including 68- 79 MGB, 67-69 MGC and 70-75 Midgets.

Your cheapest option would probably be to get a "recovered" one from Karrier. (or a new one if he has any left).

You can also preserve the originality with a brand new one from http://www.autoelectricalspares.co.uk/smiths-br130800-voltage-stabiliser-1383-p.asp @ £12.49 + VAT + P/P.

Or, ( like me ) you can go down the modern, solid state route with a "Semiconductor Voltage Stabilizer"  http://www.ebay.co.uk/itm/281132307313?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649#ht_1390wt_1142   @ £13 all inclusive.

Eh voila ! both gauges should be back to normal.