86 fuel sending unit wiring on 85 Honda Spree

[Rideslikenacho]

86 has the 3 wire
85 has the 2 wire

Do you just connect the two wires and leave the other disconnected or ground it? If left disconnected does it melt the wires or cause any further electrical issues?

[mousewheels]

The 86-87 three wire sender is mated up to an electrically different gauge than the 84-85 Sprees.
Thus the sender/gauges only function correctly as a matched set.

It is possible to wire the late sender to the early gauge, but IRC the following:
The early Spree gauge will read 2/3 to 3/4 Full when the tank is actually full
From there the Spree gauge will drop like a rock, showing "E" well before the tank is drained.

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Here's the info from the Service Manual regarding the 2 wire and 3 wire wiring and resistances.
Probe with a DMM and get the pair that reads 33 ohms (full) and 566 ohms (empty). The left over lead can be left floating.

Fuel_Measurement.png (90.45 KiB) Viewed 826 times

[Rideslikenacho]

Excellent thanks, one wire is not connected and meter shows half full when the tank is full. I’m ok with that.