mechanical oil temperature gauge not working in original GT40 - where to look first ?

Hi guys and girls,

the oil temperature gauge on my GT40 has never been working since I bought it. The instrument is of the mechanical type, with a copper or brass wire, which is inside a coil like a brake line, going from the oil pan to the instrument.

Where would you start looking to find the defect ?

Hi Chris: Lack of use may make the needle get stuck - both in electrical and mechanical gauges. I'd apply heat directly to the wire near the gauge. If the pointer moves, check for continuity of the wire from the oil pan to the gauge (e.g. physically and/or via electric resistance measurement - or test lamp) . If the pointer does not move you can carefully remove the chrome ring (bezel) and glass of the instrument (there are 3 tabs on the ring which you may have to open slightly with a small screw driver so the chrome ring can be rotated and released). Carefully check if the pointer is stuck. Usually the lube has dried. Apply heat once more and see if the pointer moves now. I'm pretty sure the instrument uses the Seebeck effect and thus should be robust. There is further information on the internet (Holden Vintage, Howard Instruments, Triumph Owners Club, the vintage Smiths catalogue, and youtube videos showing repair of Smiths instruments). If all fails, a new gauge can be had for decent money. Use original bezel. Good luck!

Here are 2 pdf files:


  • smiths-66 (1).pdf
    11.5 MB · Views: 97
  • A-Gentlemans-guide-to-Smiths-gauges_Pt_1_1v3.pdf
    813.8 KB · Views: 110
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