Thread: Fuel Selector Switch Promblem.
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Old 09-18-2009, 08:27 PM
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ctubutis
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Originally Posted by 1981FordF250 Granny
When my husband chect the switch for the tanks on the dash. The Front tank is real bright, but the back tank flickers.
No rust
Okay lets see if I can communicate these instructions. This is for the wires on the fuel tank switch on the dash. Testing with test light.

Red wire stays bright light at all times
Brown wire Nothing on top tank, flickers on back tank.
Two yellow wires nothing on top tank, flickers on back tank.
other wire (couldnt remember color) Bright light on front, back tank nothing.
__________________________________________________ ___________
Imangine this is box with wires please disregard the !!!. I couldnt get the positions of the wires right, without using the !!!

! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! *Brown Wire (ground????)


! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! *Red Wire
*Yellow Wire


*Yellow wire !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! *other wire (front tank???)
My 1981 wiring diagram shows 5 wires going to the switch...

The red wire goes to the fuse panel and provides power to the switch, it makes
sense that it's always hot.

Yellow/white stripe leads to the dash gauge.

Dark blue/yellow stripe goes to the side-mounted tank's sending unit.

Yellow/light blue hash goes to the rear tank's sending unit.

Brown/white stripe goes to the tank selector solenoid mounted on the frame
underneath (near the side tank).

Here's a test... with the key in ON or ACC,

1) remove the wire from the side tank's sender and ground it out; the dash
needle should swing all the way in one direction (I forget if it'll be full or
empty).

2) Replace that wire, do the same test on the rear tank.

If those tests pass, the wiring from the tanks to the dash gauge is good (as is
the gauge). I know you don't have questions about that but it's a way to
confirm or deny things.

The fact that the brown wire doesn't get any power on the top tank sounds OK
to me. But, the fact that it's flickering when trying to send power to the other
tank is most likely your problem. I can think of two or three possible reasons....

- The switch is bad.
- The solenoid in the valve itself (underneath, on the frame) has a bad ground
or is bad in itself.
- Bad/corroded/broken brown/white stripe wiring between the switch &
solenoid.

I will ask a really good 1981 guy to offer his diagnosis & opinion....
 
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