Now as anyone knows that owns a fuel cell, the sending units are usually 0-90 ohm units, whereas the stock unit is a 0.5-50.5 or... a 0-50 ohm unit. Now as far as I know most Subaru vehicles come with 2 fuel sending units wired in series. So basically the subaru gauge reads roughly 0-100 ohm then (or more specifically 1-5 to 100-104), and we need to run a 0-90 ohm sensor instead of 2 bulky stock sensors. With this modification you'll be able to run the 90 ohm sensor and keep very near stock levels of function.
Stock ohms vs Modified
Stock Full - 1-5 ohm
Modded Full - 7.5 ohm (reads just slightly below full)
Stock Empty - 100-104 ohm
Modded Empty - 97.5 ohm (Reads near stock)
What you'll need
-Soldering Iron and solder
-Properly sized shrink tubing
-Liquid insulation (not required)
-1x 7.5 ohm resistor
-1x 90 ohm Fuel sending unit similar to the stock one (with a floater
What you need to do
*** IMPORTANT - Make these changes to the wiring before going into the fuel cell, this way the sending unit has proper clearance at all times and you don't run the risk of blowing yourself up ***
1. Wire the 7.5 ohm resistor into one of the wires going into your new sending unit in series.
2. Flip your Fuel sending unit 180 degrees and extend wiring as needed (where the shrink tubing and liquid insulation comes in handy)
3. Test your sending unit outside the cell with another person around or yourself, when all the way up the fuel gauge should read close to or at full, at all the way down it should read empty.
Hope someone can find this helpful!
PS: You can also use a 10 ohm resistor to get closer to what you should see at stock levels for empty and it will be off by more when full.
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Originally Posted by JB91710
