Dual tank reads backwards

[tzoftx]

Just aquired a 1986 GMC 1500 with factory dual tanks. I have replaced both sending units, selector valve, and selector switch. I have checked the wiring for any tampering, none. When I push the switch to RIGHT, it switches to the left tank and visa versa. Any help would be appreciated.

 

[legopnuematic]

Is it reading the fuel level from the correct tank, but drawing from the other tank? Switch on right, drawing from left, showing fuel level for right? Or reading and drawing fuel from the left tank when on right?

If it’s reading the correct tank but drawing from the other, swap the hoses at the selector valve (both feed and return assuming it’s a 6 line switch).

 

[1lejohn]

I would think that the wiring going to the new switch is backwards, (reversed), or the wiring going to the valve is wrong. It could be someone replaced the parts in the past and got it wrong. I would switch the wiring at the switch to see if it corrects the problem. The good thing is that the switch works. You could just change the label on the switch.

 

[Jgonick]

Wiring diagram

 

[SquareRoot]

Turn the switch over. Drink beer. Carry on.