TANK AActive when de-energisedTANK BActive when energisedSELECTORSupply · return · gauge

LOGICALLY DESIGNED

Double the range without making operation more complicated.

Two fuel tanks only provide real independence when their interaction remains unambiguous. That is why the individual functions are not operated separately. One selector determines which tank supplies the engine, where the return fuel flows and which level the gauge displays.

VIDEO · 01:10 MIN Bench setup, wiring and function test of the combined tank selector.

THREE FUNCTIONS, ONE STATE

Supply, return and fuel gauge must all speak the same language.

Changing tanks is not simply a matter of switching the fuel supply. The return line must also feed the selected tank, while the gauge must display that tank's level. The three-way selector combines these tasks into one clear system.

We built the complete system in our workshop and wired and tested it as a bench setup before installation. This allowed us to verify every switching state before the technology found its permanent place in the Unimog.

Two electric three-way valves on the workbench — Supply and return each receive their own electric three-way valve.

The two installed three-way valves with connected fuel lines — Firmly mounted, connected and protected from dirt beneath the vehicle.

01SUPPLYThe selected tank supplies the engine.

02RETURNThe fuel flows back into the same tank.

03GAUGEThe matching sender appears on the dashboard.

Wiring diagram of the 12-volt tank selector with two valves, two relays and two fuel senders — The wiring diagram connects selector switch, valves and gauge into two unambiguous states.

The labelled relays R1 for the valves and R2 for the fuel senders — Clearly labelled: R1 switches the valves, R2 selects the matching fuel sender.

Wiring of the tank selector switch with red and black cables — The tank selector gives both circuits the required state at the same time.

DE-ENERGISEDTank A is active.

The safe default state works without control voltage.

ONE SWITCHAll functions change together.

Supply, return and fuel gauge remain synchronised at all times.

ENERGISEDTank B is active.

A clear second switching state – without several separate controls.

DESIGNED TO FAIL SAFE

The technology may be complex. Operating it should not be.

Valves, relays and fuel lines work together in the background. At the switch, only one clear decision remains: tank A or tank B. That is how 400 litres of fuel capacity become a robust system you can trust on the road.

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The red Unimog in the workshop — Beneath the Unimog, the completed selector system later works invisibly in the background.

Two tanks.One switch.

Double the range without making operation more complicated.

Supply, return and fuel gauge must all speak the same language.

The technology may be complex. Operating it should not be.

Two tanks.
One switch.