Earthing problem?

[EEED]

Hi,

I hope someone can help!

I have encountered an odd problem related to earthing my tachometer (I think). The car is early '66, running electronic ignition, an alternator and converted to negative earth. It has been running well with everything working. I took the tach out to try to rectify the needle sticking slightly. The only wires I disconnected were two earth leads, one from the high beam waring light (which is too short to connect to anything other than the tach fixing) and one that comes out out the loom (which I assume is the earth for the tach itself). When I reconnected everything and tightened up the clamps, neither warning light was working, so I checked the bulbs (both OK) tested them in-situ with both earths attached to one of the tach fixings. All OK. After reinstalling them, them only the main beam light works. But, in addition, I noticed that the fuel gauge doesn't work now (if anything the needle seems to want to go backwards!).

The only thing I haven't tried is connecting the earth from the loom to another instrument - the oil pressure / water temp gauge is nearest. I did loosen one of the clamping nuts on it but I don't recall an earth wire coming loose.

I have tried several times to rectify these problems but I've had enough of working from below with my head under the dashboard and very limited space to work in. The car runs well but I don't want to leave it without the ignition warning light and fuel gauge (although I don't rely on the gauge anyway, a dipstick is much more reliable!).

Any thoughts? I'll be very grateful for any advise.

Paul

[Craven]

With an alternator conversion your ignition warning light will be connected between battery + and the alternator control terminal only. Your old style fuel gauge needs a case earth to work correctly as well as the two push on terminals, pointer tending to move backward indicates a poor or no earth case connection.

[EPA]

If the earth connections were connected on the meter mountings studs it is possible that a third wire was on the stud and fell down out of sight without you realising, this once happened to me. I would also check that you haven’t inadvertently pulled another connection off adjacent to the tach.
Ed

[EEED]

Thanks Craven and Ed,

I have now got the tach, main beam and ignition light working. The main beam earths to a tach stud and the earth from the loom also attached to the tach stud. The tach doesn’t work without the earth. The fuel gauge issue was an unattached spade connection for a green lead but it only works without the earth connected to the fuel gauge!

Paul

[billwill]

The fuel gauge itself is not normally earthed, but the earth on it is needed for its panel light. That circuit is earthed at the fuel tank sender.

[EEED]

Hi Bill,

Thanks for the diagram. After my last posting I realised that the bulb in the fuel gauge had failed and after replacing it found it doesn't work without the earth. Everything is working now. It 'just' needs reassembling (for which I will need to shrink my hands). Elans certainly weren't designed with ease of access in mind.

Tanks again

Paul