Mr.T Posted July 31, 2023 Report Share Posted July 31, 2023 Good Evening Again I have another query this time regarding a fuel gauge. I sure I have read somewhere you can match your sender unit to your gauge by adding in a resister ??. The herald sender reads 16ohms and 244ohms empty / full. The gauge reads 132 ohms. Any ideas please. Thanks in advance Martin Link to comment Share on other sites More sharing options...
Pete Lewis Posted August 1, 2023 Report Share Posted August 1, 2023 is the car old enough for non stabilised gauges or has a voltatage stabiliser as sender units are not mix and match both are completely not interchagable are the needles a slow moving (stabilised ) or move instanly ( non stabilised ) voltage stabilisers control the gauges or charging voltage changes would alter the needle reading if the unit (on back of the speedo) fails you get silly high reading but igf you have the wrong sender float assy you cant solve with twiddling as the operation is very different is this 6 hole or bayonet fixed sender in the tank do make sure if it has a stabiliser that the speedo case is earthed Pete Link to comment Share on other sites More sharing options...
Chris A Posted August 1, 2023 Report Share Posted August 1, 2023 I'm not the one to help you but someone will very soon. Try the search function on the forum as this topic has been covered and I am sure there is a reply to your question. Good hunting Link to comment Share on other sites More sharing options...
Chris A Posted August 1, 2023 Report Share Posted August 1, 2023 I see Pete is awake and on your case, light at the end of the tunnel . . and no not an oncoming train Link to comment Share on other sites More sharing options...
Pete Lewis Posted August 1, 2023 Report Share Posted August 1, 2023 awake well now need a coffee for a hit Ha Pete Link to comment Share on other sites More sharing options...
johny Posted August 1, 2023 Report Share Posted August 1, 2023 10 hours ago, Mr.T said: Good Evening Again I have another query this time regarding a fuel gauge. I sure I have read somewhere you can match your sender unit to your gauge by adding in a resister ??. The herald sender reads 16ohms and 244ohms empty / full. The gauge reads 132 ohms. Any ideas please. Thanks in advance Martin The sender resistance readings seem to indicate the later bimetallic stabilised system so as Pete says critical to have the correct gauge and voltage regulator output. The latter can be checked by measuring the voltage at the supply wire (green/black) on the sender which, when disconnected and with the ignition on, should show approximately 10v to earth.... Link to comment Share on other sites More sharing options...
DVD3500 Posted August 1, 2023 Report Share Posted August 1, 2023 Since I have two Spitfires I have two of almost everything. I was thinking about trying to use a standard fuel gauge to show how full a battery is. (I know there are voltmeters etc. it is really just a thought experiment) Anyone have a clue if that would be possible at all...? Link to comment Share on other sites More sharing options...
Mr.T Posted August 1, 2023 Author Report Share Posted August 1, 2023 My herald has been fitted with a number of gauges at some time in its life. I have been tidying up some of the wiring. Gauges I guess are possible out of a spitfire. The voltage stabiliser has been disconnected and there is separate circuit board voltage stabiliser Wired in to provide power to the separate gauges. The gauges all work apart from the fuel gauge. It does work and goes to full when just power is connected. As I believe its to do with the different resistance. The fuel sender is the bayonet type and looks brand new. I can't see anywhere to adjust it. Its not a smiths gauge so there are no holes allowing you to adjust it. It's back to the drawing board and maybe some Googling. Link to comment Share on other sites More sharing options...
Colin Lindsay Posted August 1, 2023 Report Share Posted August 1, 2023 Can you bend the fuel sender arm? Might adjust the reading. Link to comment Share on other sites More sharing options...
Mr.T Posted August 1, 2023 Author Report Share Posted August 1, 2023 Could be a possibility as you can read the resistance as you move the sender arm. Not sure how that would effect the empty reading. Have found the gauge is empty 10 ohms and full is 180 ohms. The sender is 16 ohms empty and 244 ohms full. How you adjust the gauge is the question. Might bit the bullet and take gauge apart and see what's inside. Link to comment Share on other sites More sharing options...
johny Posted August 1, 2023 Report Share Posted August 1, 2023 Are you sure the gauge is a smiths instrument as the resistor values you have found to give empty and full correspond exactly to those of a Euro type sender.... Link to comment Share on other sites More sharing options...
Mr.T Posted August 2, 2023 Author Report Share Posted August 2, 2023 It's a copy of smiths so probably a euro version as you say. Hopefully it can be adjusted Link to comment Share on other sites More sharing options...
johny Posted August 2, 2023 Report Share Posted August 2, 2023 Are you sure about those sender resistance readings as the correct Smiths sender should show 240ohm empty and 20ohm full so has no chance of working with a Euro type gauge... Link to comment Share on other sites More sharing options...
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