I keep preachin' this
You need to think of your gauges as a SYSTEM
The general path is
ignition switch (switched 12v power) --to PC board connector at cluster,-- via PC board to voltage limiter socket -- through limiter --(5v output) --back out to PC board limiter socket -- and goes via PC board -- to fuel, temp, and oil gauge if equipped, -- connects to each gauge with stud / nuts -- through each gauge, back out the sender side of gauge(s) via stud/ nut -- via pc board to PC board connector -- through harness connector --
for oil (if equipped) and temp -- sender wires out through bulkhead connector -- to sender connector -- to sender -- to ground
for fuel, down to kick panel connector, back on rear harness to tank sender connector -- through sender -- to ground
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The above is IMPORTANT to think about, because this SYSTEM is a big long CHAIN, and as you know, one bad link in a chain "breaks" the entire chain.
Fortunately, it's fairly easy to check. You can check everything "back to" the sender connector as a first dividing point.
As said above, a real quick check is to ground the sender wire, switch on the key, and watch for a few seconds. Gauge should SHOOT to full, don't leave the switch on for long.
If you want to be more accurate, go to RadioShack and buy some resistors. You want three resistors to check the gauges at full, 1/2, and MT or cold. All three gauges, oil, temp, fuel, check the same, same resistance.
But a combo of resistors to make up about 11-15 ohms for the "full" check, about 23--25 ohms for the "1/2" check, and about 70--75 ohms for empty
For example, buy a pack of four 100 ohm, 1/2 watt resistors at Rad Shack. Wire all 4 in parallel, and this will make one 25 ohm resistor. Clip this from the sender wire to ground, leave the key on a minute, and the gauge (if the gauge, limiter, wiring is OK) will read 1/2 full.
If so, now you know you have sender troubles. The sender could be a repop, which have known problems, or could be and original which is basically worn out or gummed up
If you can drain the tank to the point where "it's out," the sender should measure 70--75 ohms if accurate.
If you fill the tank, it should read 10-15 ohms.
Pretty difficult to check 1/2 in the tank, unless you have determined for certain what it holds
