Mad Scientist Posted March 21, 2021 Share Posted March 21, 2021 Hello folks, The fuel tank now only registers 1/4 full. I'm told its likely because the indicator potentiometer windings have failed, and they are poorly constructed in the first place. Has anyone ever managed to replace this unit or, for that matter, the sender unit in the fuel tank? I know its easy to look into the tank to check the fuel level, but I'd like to try and rectify the problem. Any advice gratefully received regarding fault-checking. If any one has a spare dud instrument panel that I could look at, I'd be very grateful to hear from you. Clive remarked in a separate post "Is your Switchboard No.1 still a Mk 1 or has it been upgraded to Mk 6?". Can anyone please tell me how to tell the difference between the two. FV numbers gratefully accepted. cheers, Mad Scientist Quote Link to comment Share on other sites More sharing options...
wally dugan Posted March 21, 2021 Share Posted March 21, 2021 HAVE you taken the sender unit out of the tank and checked it is free to move as if the vehicle been has stood for a while this can happen take the engine cover off to gain better access disconnect the wires and leave the potentiometer in place until you check as it can be a pain at times to relocate Quote Link to comment Share on other sites More sharing options...
Mad Scientist Posted March 21, 2021 Author Share Posted March 21, 2021 Wally, thanks for this. I've moved the float arm with the aid of a stick and its moving freely. Since my post, I've found instructions in EMER V623 Unit repairs, Chap 10, page 8-9 and Para. 19 to check voltage and resistance between the three terminals of the tank sender unit as 400 ohms. The resistance between pairs of cables at the instrument panel end should be 600 ohms. Any further information that I find, I'll post on here. Quote Link to comment Share on other sites More sharing options...
Mad Scientist Posted May 24, 2021 Author Share Posted May 24, 2021 As an update to my post, with an electrical engineer friend I checked the ohm values of the tank sender unit, and of the torroidal coil, plus the wires which go forward into the Ferret driving compartment and connect to the wires going into the instrument panel switchboard at the connection cluster by your right knee. We also removed the sender unit and bent the float arm because it was obstructing on the side of the fuel tank. WE had to bend the float arm; we couldn't rotate it wrt to the sender unit by loosening the screws of the two clamps at the top and bottom of the grey tube connecting the sender unit to the float arm. Once the free movement of the coark float was fixed, we cleaned the top pin holding the two rotating contacts on the sender unit with WD40 and established that this was working on all three sectors of the wound torroidal coil. Wggling the wires in the right-hand electrical cluster we found that the instrument dial went from full to empty the wrong way round under the gauge, and then suddenly it went OK, around the top. So, the carbon coating on the magnets in the meter on the instrument panel is OK; the sender unit and its wiring are all OK, and its just a poor positive feed connection at the cluster. I’ve also included a photo of this with the FV-number, plus a photo taken from a descrition of the Austin Champ to show the float arm assembly. Also read this link http://www.austin-champ.co.uk/mech/fgjacksn.htm and this http://www.austin-champ.co.uk/mech/fuelgage.htm Hope this helps, Mad Scientist. Quote Link to comment Share on other sites More sharing options...
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