Petrol Tank Sender Unit

Steve Welton · Joined: 17 Oct 2013 Posts: 105

My fuel gauge did not work. Subsequent investigation showed the gauge to be OK but the sender unit not. As I was dipping the tank to check fuel level I removed the sender unit and put on a blanking plate so that I could continue to use the car.
I dismantled the sender unit to find that the wiper had worn through the potentiometer windings years before ; a previous owner had been in there and broken the potentiometer curved track around which the windings are made. So before I spend time effort and energy in attempting making a new track and winding it I seek the following help.
1. Has anyone a spare sender unit they would sell?
2. Has anyone knowledge of a fix using a potentiometer ( or possibly a complete unit ) from a more modern application?
3. Are there any good repairers out there that might know of a fix.

NB Christopher has already advised me of Speedy Cables

John Murch · Posted: Mon Mar 19, 2018 6:32 am Post subject:

Have you looked at one of these.
https://www.holden.co.uk/displayproduct.asp?pCode=070.233
Or
https://www.holden.co.uk/displayproduct.asp?pCode=070.011

Steve Welton · Joined: 17 Oct 2013 Posts: 105

Thanks John these are helpful suggestions that I will look into. I think the difficulty would be that the gauge is designed to work with a sender that has a range of 0 -35 ohms in the arc that the wiper covers. I can probably find a way of adapting the values if I can get something that will mechanically fix.

The sender unit for the Bentley is not dissimilar to those used in Spitfire fuel tanks ; I am exploring that route.

Steve Welton · Joined: 17 Oct 2013 Posts: 105

I am now looking into adapting a more modern top mounted sender unit. In looking around at these I see that the coil and wiper elements of the unit are inside the tank with the electrical connection outside.
Surely there is the possibility of some sparking as the wiper tracks across the windings ..............if this is the case then when sparks surely petrol vapour would ignite and there would be a big bang.
There is clearly something I have not understood here.
Can somebody reassure me about the safety of this set up. It has to be safe but what is the science behind it?

Robert Craven · Posted: Fri Apr 13, 2018 2:55 pm Post subject:

Christopher Carnley · Posted: Fri Apr 13, 2018 4:04 pm Post subject:

Steve Welton · Joined: 17 Oct 2013 Posts: 105

Thanks I have done the Google searches and you are right several people ask the same question and there are some answers which BECAUSE they may or may not be right are not particularly reassuring. Before using a modern sender unit with exposed electrics I thought I might find someone on this forum with the answer.

I know there are some suggestions for how to repair the sender units but no definitive advice on winding a wire wound pot to be tracked through a semi-circle or on where I might find a track of the appropriate size and the gauge and length of the wire needed to produce the correct resistance. However I am not deterred I will find a way somehow of fixing this.

Many thanks for all the useful suggestions.

Stephen Blakey · Posted: Fri Apr 13, 2018 4:32 pm Post subject:

Just to remind folks; you can enlarge web pages by holding down the ctrl key and repeatedly pressing +. Ctrl 0 (zero) restores the original size. The above was legible on my screen after zooming in.

Stephen Blakey · Posted: Fri Apr 13, 2018 4:42 pm Post subject:

Steve Welton · Joined: 17 Oct 2013 Posts: 105

Thanks Stephen I have the voodoo sorted