Ruby gauges

[Merlin0161]

Hi all.
My '37 Ruby has issues with its gauges.
The fuel gauge intermittently shows full, empty or somewhere inbetween regardless of how much fuel there is in the tank.
The ammeter is stuck on full charge.
So my first question is about the fuel. On mine there are three wires. One to each pole and one, I'm assuming is earth to the screw holding the bracket to the back of the gauge.  I have disconnected the "earth" and the gauge still reads full, I shorted the gauge with a piece of wire and it read around a 1/3rd of a tank, which would go with what's in there. So, bad earth is my guess as to the problem. 
Next question,  were the gauges just fitted straight into the metal dash board piece or did the gauges have a rubber seal around them. Or were they earthed through the case and the steel dash?
Next, ammeter. It's not working at all. Does anyone out there have a spare that they would be willing to part with or does anyone know of a reputable repair service.
Thanks in anticipation of help.
Regards, 
Carl.

[Bob Culver]

Tinkering with fuel gauges it is prudent to be careful. The mechanism is inside the tank and any gross error might produce heavy sparking.  
(It always seems a miracle these with a sliding contact operate without ignition problems)

[Howard Wright]

Hi Carl

Probably not for the purist but I replaced the ammeter on my special with a modern reproduction.  Classic motorbike suppliers stock varying types of both 12 and 6 volt instruments.

The repro gauge was a tad bigger than the original and considerably deeper so the switch unit needed some modification.

Cheers

Howard

[Colin Morgan]

The original ammeter I took out my Ruby is a very simple device - not much to go wrong - if the pointer is free it has to work? The one I put back in is the same size but has a later plastic case - it ranges from -30 to +30 amps. These seem common enough, as are the older -20 +20 ones - there are always one or two about for sale?

[John Mason]

Hi, with reference to the part of your thread regarding bad earth. I had this with my Ruby and tracked it down to a number of loose connections all on the back of the instrument panel. If I remember correctly the earth wires all for the gauges and dash lights are linked together and fastened with small nuts which in my case were all loose hence the bad earth. I tightened them and also installed an earth wire from one of these to a good earth on the body just in case the instrument panel itself was not making a good earth. Problem solved ammeter and fuel gauges working and the dash lights.

John Mason

[GK5268]

Next question,  were the gauges just fitted straight into the metal dash board piece or did the gauges have a rubber seal around them.

There was a rubber gasket that fits in the groove pressed into the instrument mounting panel, I used a round sponge seal, I think from memory, this was about 5mm or 6mm in diameter, compressed nicely when screwed in position. For the fitting of the gauges into the mounting panel, these appeared to be a direct fit, there is a rubber ring for instrument glasses to give a snug fit, otherwise the glass would rattle...

As a stop-gap for the ammeter, I bought one of modern manufacture (of the correct mounting hole diameter) until I managed to get an original correct one, the modern worked well enough and looked perfectly in-keeping. An original looks lovely though!

When you take the instruments out, it is an opportunity to remove the old back-light diffusers, I used blue acetate sheet & cut the strips - brings the instruments to life after dark!