Fuel gauges

edited July 2015 in LINKS
when at the Treffen I consulted with Wizard Bennet regarding a white wire that was dangling down under my platform mid ships. My fuel gauge doesn't work and I thought that might be the problem as it was dangling in fresh air and might have been the feed wire. Now back, and tidying up some bits and pieces ( including the horn that turned out to be a short circuit between the feed wire to the button that was making whenever I dipped the clutch. Now it's one inch shorter and properly insulated and routed, problem solved.) I have now found the sender on the top of the tank, and nothing attached to the spade connector. Making a circuit back to the white wire did not give any activity at the gauge. My circuit diagram, and the one published in the magazine, do not show any wiring for a fuel gauge. My gauge looks like it was factory installed so does anybody have any info on how it should be wired up please? I think the white wire is for a reserve valve, so not used on my 73 Polycab.


  • Nigel,

    I'll have a look at the fuel gauge circuit on Lurch this weekend. Glad you found the real cause of the horn issue.
    Did you take the tool box off to find out where the white wire went? Could be that it is not connected at either end!
    Have you put a meter across you battery without the engine running and recording the voltage. Then the same again with the engine running (above idle)? That should give you an indication of the charging status of your Dynastart. Shouldn't get a flat battery when the engine is running!
    How good is the battery? Could always be a duff cell in the battery which is the underlying cause!

  • Thanks John. Have changed the regulator for a good spare. The contacts in the old one were well burnt out. All now fine. Charging light now goes out much earlier and stays off during normal running. At least this has confirmed the Dynastarter is ok. But I like the idea of the electronic one and they do a kit with new solenoid as well, so it on my list.
    The white wire had a bullet socket on the end and not a spade so I don,t think it was meant for the fuel sender. I am away racing this weekend so it will be next week before I can get the tool box off so no urgency for the gauge. It's been like that for a while but any info will be helpful.

  • Nigel,

    You can "service" your existing solenoid - I pretty sure I did a "how to" that's on here, or is it in the magazine? Either way not a difficult job if you have a 100 watt soldering iron. Or one of those that you put in a flame to heat.
    The electronic ones from the place I bought mine do a "DIY" unit which is just the circuit board - no case, or if you send them an old one, they can hide the electronic gubbins inside that and then it looks original!

  • My fuel gauge is proving interesting. The gauge now shows full even when there are no wires connected. I have tried lots of different combinations of connections on the back and nothing makes any difference. I have even taken the fuel filler cap off and waggled the float again to no avail. So I don't know if its the gauge or the sender. The white wire that John found goes back to the gauge and is now properly connected right through.

    And I thought having a Hafi was just going to be a physical challenge - my brain hurts.
  • If the gauge shows full with no power, then it must be faulty in some way. The problem is that everything is held in place by the rolled over rim, so you would have to very carefully lever the rim up all the way round to release it from the lip on the body of the gauge. The remove it and the glass and what ever sort of gasket is lurking in there before removing the internals.
    More than likely they are just gummed up from having been sitting still for so long. The internal are "sort"  
    of open to the element in that the bulb unit is just a push fit in a hole in the back.

    It is possible you have the wire going to the gauge on the wrong side of the sender - the sender is basically a variable resistor and it might be that the gauge is expecting 12 Volts for full meter movement and proportionally less for other positions on the dial.

  • edited December 2015
    Have finally got to the bottom of the problem. The gauge is goosed. I had an old Smiths fuel gauge and put that on and it showed half a tank, which is what is there according to the Mk 1 piece of garden cane. So here I am looking for a new (?) VDO gauge, preferably with the original Austrian wording. Its got leer und voll for empty and full, and is a Kraftstoff gauge (thats fuel). Have searched on the Austrian, German and Dutch ebay sites and not found anything yet. The regular suppliers don't have any stock either. For the moment I will use the Smiths unit with a conversion ring, its 52mm and the VDO unit is 60mm. It may be there for a while.

  • Nigel,

    If you want I can send you a fuel gauge, not sure if it has German or English on it's face. It could of course wait until we next meet and I bring both it and the sump guard along....

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