Testing fuel gauge/sender circuit

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DyeingSwan

Testing fuel gauge/sender circuit

Post by DyeingSwan »

:banghead
OK, so when I got my '67 D100, the needle on the fuel gauge never would move off of "E", or actually below "E". Now, I have replaced the gauge with a supposedly good-used one, and the problem remains. There is nothing, repeat NOTHING in my P.O.S. Chilton's manual about how to test the gauge and sender circuit... like as in they just politely bypass all mention of it in the instrument troubleshooting section. :censored

So here is what I'm getting. At terminal "I" on the gauge, which I assume is Ignition, I am getting a nice steady 12 volts when the car is off an 14 when it's running. At terminal "A" on the gauge - Alternator? I am getting a constantly fluctuating volatge reading whether the car is on or off - seems like this would make sense if it is the alt terminal. Finally at terminal "S" - sender? I am getting... not a gosh darn thing, and I'm testing it right at the post. Likewise, I am getting no voltage at any time at the sending unit, and I disconnected the wire midway to test that terminal - no voltage there either, although that would make sense I guess since there's no voltage reaching it through the gauge, if "S" really stands for Sender. So I guess my question is, have I got a bum gauge? I need to know ASAP so I can send this :censored gauge back and get a refund!

Many thanks again,
Courtney

DyeingSwan

Post by DyeingSwan »

Update... paging through this forum it looks like DB69 had a similar problem with his fuel gauge, and from the suggestions given there I was able to determine that indeed it was the used gauge that was causing the problem - so it went back to the supplier today. :clap (applauding my own ingenuity... kidding) Thanks anyway!

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mesman
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Post by mesman »

Courtney,
I had the same problem. Although mine is a '67, I believe they work the same. If you still have the same problem after installing a new gauge, try grounding the wire at the sending unit, (with the other end still attached to the gauge and the key on). If the gauge is good, it should immidiately go to full. My problem turned out to be the sending unit. Hope this helps!
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Jeffc
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Post by Jeffc »

Above post is correct, pull the plug off the sender wire at tank and
ground it to the tank, needle on gauge should peg......
Back of the gauge......
I is imput and should be feed by buss bar off the
alt gauge and read steady 12 to 14 volts
A is accessory and runs power to temp gauge
and should pulse 0 to 6 voilts
S is to sender
You can also ground at the S pulg-in and gauge should peg
If gauge does not peg ether way after grounded then
it's bad
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