Ruby Fuel Tank Sender Unit Problems

[DaveT]

I have a problem with Fuel Tank Sender Unit on my 1935 Ruby.
 
The float was found to be part full of fuel and the arm on the sender unit snapped when removing the float. (That’ll teach me for being heavy handed)
 
So the question is has anyone ever replaced the sender unit with a modern equivalent or can you still source original replacements.
 
Also does it matter if it’s 6v or 12v as it’s only a rheostat that produces the reading?

I don't fancy resorting to a stick down the filler to check the level.

Any and all ideas gratefully accepted.

[Nigel Ricardo]

1970 Midget / Sprite (12 v) fits, but keep the float to the driver's side as the other way round touches a tank baffle.

[DaveT]

Thanksfor the info Nigel, I take it that the holes are in the same position so it's a straight swap and I've found them listed on eBay https://www.ebay.co.uk/itm/143106015973#vi-ilComp.
Cheers
Dave

[Nigel Ricardo]

Yes, the holes line up, remember to keep the float to the right of the car, the arm will also want bending down a bit.

[John Cornforth]

Hi DaveT

The original Ruby used a Smiths Moving-Iron Gauge and a Sender with "Maximum Resistance equals Full", the Resistance range being about 0 to 30 ohms.

Around 1935 Smiths changed to using "Maximum Resistance equals Empty", sticking with 30 ohms.  These were used by Morris among others.

Later still, for 12 volt systems used right up to around 1960, the Resistance was increased to 70 or 80 ohms.  The Sprite and Midget ones are this type.

I suggest you wire up any replacement sender with your current gauge with the sender out of the tank to begin with, and make sure it gives sensible readings as you move the arm.

One option is to keep the original sender body and rheostat (assuming it works), but replace the float and arm with one from a later model.  Wire arms can be joined together (with overlap) by using the innards of an electrical terminal strip connector, or by binding with wire and soldering.

Cheers,  John.

[DaveT]

Thanks for the suggestions, I've ordered the Smiths Sender Unit BHA 4711 and I'm going to temporarily extend the existing wiring so that I can sit comfortably in the driver's seat and try both of them to determine any differences in their function etc before finally fitting to the tank. 
Luckily a long time ago I cut a circle in the back seat floor pan above the sender unit to allow easy access then fitted a covering plate., so fitting and removal is very easy peasy. 

I'll let everyone know of the final outcome and any and all adjustments necessary to mimic the original. I'm very grateful to both Nigel and John for the useful input.
Cheers
Dave

[Mick Hanna]

In the hope you might notice this, Dave T, could you tell me the diameter of the access panel you cut to reach the fuel sender unit, please? I need to examine mine to sort out a fuel gauge that doesn't register more than half a tank. Lying on my back beneath the car and trying to remove those screws on top wears me out just thinking about it. I've marked out as best I can where a hole needs to be cut in the floor-pan beneath the rear seat squab, but I'm wondering how wide it should be to be workable?

["Slack Alice" Simon]

5.5" cover over a 3.75" hole, on my '34 Tourer

   

   

[Mick Hanna]

That's tremendous. Thanks, that really helps.