strange fuel readings

[dvdswan]

ok, so I will try to explain this the best I can but I confuse myself. 
1st off truck switches tanks with no issues.  I've been pondering this for a couple of days now and tested it today to verify the issue.

to start I had 7/8 fuel in each tank, started on the left side tank (according to the switch) and went to the j/y.  arrived there and the fuel gage was still showing 7/8 of fuel.  I switched to the right side tank and it showed 1/2 tank.  so on the way back I left it on the right side tank (according to the switch) got home and the right side tank was still showing 1/2 tank switched to the left tank it was now 1/2 tank as well.

so apparently I have wires switched somewhere, either on the selector switch itself or the at the firewall connection (I'm guessing, I don't know where the wires go through as of yet). 

my question is can I swap the 2 sender wires at the selector switch terminal 3 and 5 for the aux and main tank senders to solve this or is it more than that?

term 3 wire is labeled 18 LT BLU - 30B AUX TANK SEND
term 5 wire is labeled 18 TAN/W - 30C MAIN TANK SEND

control switch is labeled as
1-IGN FEED
2-SOLENOID
3-AUX TANK SEND
4-GAGE
5-MAIN TANK SEND

[bd]

30B should be connected to the left (auxiliary) tank, 30C is the right (primary) tank.  You should be drawing from the left tank with the solenoid energized.  If you reverse the wires at the switch, you'll effectively make the left tank the primary and the right tank the auxiliary.  Are you certain that someone didn't switch the hoses at the selector valve?

[dvdswan]

I pulled that info from the 78 wiring diag manual.

but what you said makes sense to me and I think I see what my issue is now.  when I replaced my selector valve last month the new valve was opposite from the original.  by that I mean, the solenoid was on the opposite side of the feed lines so when I hooked it up the main tank is now the left tank and the right was the aux tank according to the fuel hoses as they were connected.  left tank is now closest to the solenoid and the right is now furthest.

so if I switch those 2 wires that should fix my problem, is that correct?

the selector valve is a single lead valve so as it is engaged it will switch to the aux tank.

[bd]

Swapping the two wires at the switch will restore proper function.  Just remember the primary and auxiliary tanks will be reversed.  Happy switching!

[dvdswan]

thanks for the info.