Dual tank not switching over 1986 C 10

[akart]

Second tank not switching over stays on same tank regardless of switch position. Looked at my fuse block and do not see a fuse. Is there one?
Would appreciate any help and what to try. Thank you

[TexasJeff]

The valve under the truck is more than likely bad, you can still buy that valve from a dealer, I believe there are 2 different ones, a 6 port and 3 or 4 port.

[hatzie]

Before you start swapping expensive parts test things.

On a 1986 it's a 20A ATC fuse marked IGN but I bet it's OK. Ground to the switch is from the Buss bar above the E-Brake pedal.

Usually the problem is the dash switch. It's easy and cheap to replace. If your truck still has the old 81-86 momentary switch that says "DEPRESS FULLY" I'd upgrade to the AC Delco D7089C maintained switch that's listed for the 1987-1991 RV series TBI trucks. Honestly... I'd upgrade to the newer maintained position switch whether the old switch is testing dead or not.

If the new switch doesn't fix the problem break out your volt meter and some alligator clip test leads.
Buy a couple Male and a couple Female Weatherpack terminals. NAPA usually has them. With a few loose terminals and some alligator clip test leads you can safely probe unplugged Weatherpack connectors without damaging them.

Check the power and ground at the dash switch connector with the ignition on.

• Pink +
• Black -

The green wires control the valve with a good switch. The switch position sets the polarity of the Light Green and Dark Green wires at the valve to reverse the permanent magnet DC motor in the valve.

• Select LH.
  • Light Green is +
  • Dark Green is -
• Select RH.
  • Dark Green is +
  • Light Green is -

If you have the proper volts at the green wires the valve is probably shot. It's worth noting that an old shagged out switch can sometimes pass enough volts to drive a meter but not the valve. Before you change out an $80-$115 valve swap in a new $15 switch.

[RUN GMC]

TexasJeff is right there are 6 slots on the connector which come in 5 and 3 port styles....Rockauto has a cheap option and the AC Delco option......have one on my 87 GMC but never had to replace it...........

[hatzie]

Originally Posted by RUN GMC

TexasJeff is right there are 6 slots on the connector which come in 5 and 3 port styles....Rockauto has a cheap option and the AC Delco option......have one on my 87 GMC but never had to replace it...........

Hookup diagram...Pollack Motorized Valve Install Instruction Sheet PDF
If it turns out that you need it get the AC Delco Professional grade U7001 valve. Amazon is a pretty decent deal if you have Prime. Otherwise Rockauto is a better deal.