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Hi,
I have never thought about polarization to a resistive load but 240s don’t have low fuel lights.
Warning: I’m not familiar with the 700 or the 900 series but I cannot help thinking that they are built internally in a likewise fashion.
The low fuel light is out of my league.
It probably involves a transistor circuit that either responds to a Voltage drop reading or grounding current?
How it triggers backwards well, it just might be polarity?
Trick is how did that happen with plug and play socket systems?
On a 240 the gauge can get wacky.
Actually it is the wiper finger is “over traveling” a coil of resistance wire inside the sensor housing.
The wiper finger is not centered on the resistance block with the float arms travels.
Rare but there could be a dirty wire section from gelled fuel at either end too and it loses contact.
To me it’s unusual to have it happening at both ends.
Slipping off the top it will say empty, when it’s totally filled, until some fuel usage drops and it back down on the wire.
With that it can show empty too late as the reserve section is raised and there will not be as much.
Losing a contact to the wire causes the gauge needle to fall down because lack of current stops heating the gauge up.
240s can have this happen if the float arm gets bent or is missing one or both a limiting stop tabs on the outside of the sender housing.
Has the cars gas tank ever been heavily jolted while it was nearly empty of fuel?
The float can bobble around pretty violently and the gauges do not respond very quickly.
Driving too fast pass through some open ditches, used for rain control above ground of city streets, can do it.
I’m sure someone will have seen this on a 700 and hopefully will clue us both in with their experience or knowledge of the 700.
It seems like it’s on the sensor end rather than a polarity issue.
I wonder why the in-tank pump, if there’s one, would not be affected in this case.
Four wires means two circuits so maybe?
Phil
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