Any ideas?

In message , Jim Warren writes

It's possible that you might have broken the ground connection to the instrument voltage stabiliser. In Triumphs of this age, it's a medium-sized metal 'beetle', whose ground connection is usually to the case of the speedo. You did re-connect the black 0V connection to the speedo case didn't you?

I thought I had. But I have just turned the side lights on, and the panel lights for fuel gauge and temperature gauge light but not the speedometer. It seems too much of a coincidence to imagine that the bulb has blown, so my guess is that I somehow dislodged the earth.

Back to the screwdrivers and scratched hands!

Thanks for the pointer.

Jim

It is the Saloon

I might easily have dislodged either the bulb or the earth connection when I had my hand behind reconnecting the trip meter cable and then pulling the air vent tube back to its position on the back of the vent.

For the moment, I am assuming Chris's explanation is correct. Why assume two faults when one would cause the same symptoms?

Interestingly, the old speedo cable had metal ends, the new one has plastic. So I am beginning to wonder whether the old cable made an earth connection from the speedo casing back to the gearbox and the new one doesn't. It is at least as plausible as the idea of pulling a wire off - although it is very cramped behind the dashboard, what with the main wiring loom and air vent tubing in a small space, and it took a good push to get my hand behind there.

Dashboard out and checks with a continuity tester, methinks.

Jim

Maybe the proper earth wire has been dodgy/disconnected for quite a while and the old speedo cable was acting as an unofficial earth lead?

Ron Robinson

That was my thought too. I will check all the instrument earths while I am at it. The rev counter panel light doesn't look as bright as I expect either, so a dodgy earth is a distinct possibility.

Jim

I thought you would like to know that your diagnosis was correct (ish).

The ground connection was apparently in place, but the spade was a very sloppy fit and a meter across the connection showed a high resistance. Cleaning the contacting surfaces and tightening up the grip fixed the problem. The temperature gauge behaves normally again.

So thanks for the pointer. If I hadn't known to pay special attention to that connection, I would have seen it in place and assumed it was OK.

The sad thing is that having got the voltage stabiliser working properly, I have suddenly "lost" a quarter of a tank of fuel.

Jim

Glad to have been of help. I ought to have thought, the non-working voltage stabiliser would have made the fuel gauge read high as well! It's something that happened to me when I had a Vitesse.