The tempo fuel gauge on out 376 1996 has gone to eratic reading. bouncing all over the place but seems to like 3/4 full-- only reading nor acheived is full. Many seem to think it's a bad ground Question is where and what is the tank grounded to and how is the ground wire routed? Any insight is welcome!!
Wild and crazy fuel gauge
- Thread starter Mark Juetten
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With most all Tempo, now Moeller, sending units they do not need to be "grounded" to work. There is a loop that reads resistance. The resistance scale is 33-240 Ohm's. The center conductor on the sending unit is the send for the "S" terminal and the wire connected to the bolt on the outer edge of the sender plate is your return which goes to the GND terminal on the gauge. Of course this is only reading resistance so these wires can be backwards and still work. Despite this only being a resistance circuit you still need good connections but it is a lot less critical than a circuit that has 12V and amperage running through it.
That being said these senders are horribly un-reliable. The Wema type (Moeller calls them Reed Switch), or mechanical type with electronic sending capsule are far more reliable. The problem with the typical cheapo tempo/Moeller senders is that there is a sending unit in the tank exposed to fuel. They simply wear out and die and I just replaced one today! The Wema and mechanical versions are sealed and I have never experienced a failure of either type though I do prefer the mechanical type as even if your gauge fails you can still manually read the level of fuel in your tank. The boat I repaired today got a new mechanical sender with electronic conversion capsule.
Don't be fooled if you get a decent resistance reading across the center stud and the cover plate. I have seen this before and the senders can still be kaput. There is enough resistance to read on the meter but not enough to make the gauge work. If you remove the sender put a DVM on it and move it from empty to full and you should see 33-240 Ohm range if it is operable. They usually show nothing as the one I replaced today did and that's how you know it dead.
If you place a jumper between the "GND" pin and the "S" pin on the fuel gauge the meter should peg. If it does the gauge is likely fine and the issue is your sender.
Clean all connections first then if still erratic start trouble shooting the sender and gauge.
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