Just the hot lead to the gauge needs a voltage reducer, not the sender.
Most troubles are that the sender mounting flange is not grounding. The fix for that is to add a wire from a sender screw to a nearby frame spot.
See if that helps. The system is not real accurate. If you have a half tank +/- a 1/4 of a tank it may read 1/2 ish.
If you still want to test them together, it can be done but you will have to pull out the sender.
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn
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