Quote:
Originally Posted by bigred1957
Resistance makes sense, both my new and old rheostats do the same thing. The full sweep ranges from empty to just above a quarter tank, but it still is a full sweep (i.e. the gauge isn't stuck at a quarter a tank until the tank reaches a quarter, it sweeps the entire capacity of the tank). Wouldn't that mean added resistance in the gauge or printed circuit?
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First of all, I'm pretty sure I had it backwards. 0 ohms is empty, 90 ohms is full (mods, can we edit my last post in this thread, then also get rid of this disclaimer for future people searching for answers?)
Additional resistance would just read higher. Instead of ranging from 0-90 ohms, you'd be ranging from 60-150 ohms, so your tank would always look more full than it is. You'd basically read from 3/4 to full.
Is it possible you have an old 30-ohm sending unit? They were used I believe before 1965.
You can do some really simple tests to check the gauge. Pulling the wire off the sending unit should peg the fuel gauge to full full full. The gauge is expecting to see 90 ohms at full, and you're showing it a million ohms (open circuit).
Likewise, taking the wire from the sending unit and shorting it to ground should peg the gauge at empty. The gauge is expecting zero ohms at empty, and that's exactly what you're doing. Sending it to zero ohms.