ISSUE with '77 Fuel Gauge Switch

[302]

Hey Guys,

The dash switch on the gauge to monitor the fuel levels in the two tanks has stopped working properly. It will now only monitor one of the tanks. The other tank just reads "empty" even with a full tank.

Anybody have any suggestions or experience with these?

Thanks very much.

 

[Blue Bastard]

I would bet its not the switch. It might be the sending unit for the tank. Put the switch to the tank that is not working and see if you have and pulsing voltage (4-9)at the plug for the sending unit at the tank. If you do then you know the switch is working and the sending unit has issues. no pulse, Then its up in the switch area.

 

[oleguy74]

which tank?maybe lost ground at tank.check wiring first.

 

[DirtDonk]

To add to what was already said, while it's possible to be other things, it's still VERY possible for it to be the switch. They fail with unfailing regularity. And if yours is the original, it's given excellent service.

The only things you can be sure it's not are the gauge itself and the wire between the gauge and switch. Anything after that can be the culprit.
First thing to do then is start testing. Get your handy-dandy volt/ohm meter out (you DO have a volt-meter, don't you? ;D ) and start having fun.

1. Switch.
2. Wire from switch to Aux sending unit.
3. Sending unit
4. Ground wire between sending unit and body.

You could eliminate a few of those things quickly by swapping wires at the switch. One tank for the other.

Paul

 

[Steve83]

Another way is to just bypass the switch temporarily: pull the gauge wire & 1 tank wire off the switch terminals, and join them. Don't let them touch ground while the key is on.

 

[DirtDonk]

Do you know which tank is not reading 302?
Like Steve said, you can bypass the switch. It's super easy to do for the main tank, as the harness is the same whether you have single or dual tanks. So there is an Orange wire with a funny looking 90° push-on connector right there by the switch. Find the matching 90 degree connector that's sitting there nearby, and simply plug them together.
This is how it's wired if you don't have the switch.

I forget just how the wires are oriented with the switch, but it will be pretty obvious what to do when you see the connector I'm talking about.

Paul