Charging System Troubleshooting--Blown Ignition Light Fuse?

[ACHiPo]

Disconnected the double green wire from the ignition light, replaced fuse, turned key. Blown fuse (ammeter jumped then dropped to 0).

Disconnected the 10 ohm jumper and the single green wire (ignition light and jumper completely out of the circuit). Replaced fuse, turned key, fuse blew.

[patrickt]

Originally Posted by ACHiPo

Disconnected the 10 ohm jumper and the single green wire (ignition light and jumper completely out of the circuit). Replaced fuse, turned key, fuse blew.

Alright, leave the ignition light and jumper completely disconnected, taped off, and out of the circuit. We will now try and use your tool to locate the short. Coming off of Fuse #3 there are two "legs." One is a W/G colored wire and the other is LtG colored. The latter goes to the heater switch. The former goes to the wiper switch where it becomes a Gn color and from there forks off to the wiper motor and fuel/tach gauges, respectively.

What we will try and do with your tool is to get an idea about where the short is along these lines. Once we get it in the ball park, we can definitively isolate it with a surgical cut to a wire that is easily mended. Put your tool across Fuse #3, turn the key on and observe the circuit breaker clicking on and off. Then put the inductive gauge along the wires as they pass through the firewall and traverse along the path above. Make a note of the behavior of the gauge along each portion of the circuit and report back.

As you're doing this, keep an eye out for an "easily cuttable and mendable" spot on the green wire. I know you don't like the idea of snipping wires, but it's likely that we'll end up doing that. And cutting anywhere along that line limits the potential short locations.

[ACHiPo]

Originally Posted by patrickt

Alright, leave the ignition light and jumper completely disconnected, taped off, and out of the circuit. We will now try and use your tool to locate the short. Coming off of Fuse #3 there are two "legs." One is a W/G colored wire and the other is LtG colored. The latter goes to the heater switch. The former goes to the wiper switch where it becomes a Gn color and from there forks off to the wiper motor and fuel/tach gauges, respectively.

What we will try and do with your tool is to get an idea about where the short is along these lines. Once we get it in the ball park, we can definitively isolate it with a surgical cut to a wire that is easily mended. Put your tool across Fuse #3, turn the key on and observe the circuit breaker clicking on and off. Then put the inductive gauge along the wires as they pass through the firewall and traverse along the path above. Make a note of the behavior of the gauge along each portion of the circuit and report back.

As you're doing this, keep an eye out for an "easily cuttable and mendable" spot on the green wire. I know you don't like the idea of snipping wires, but it's likely that we'll end up doing that. And cutting anywhere along that line limits the potential short locations.

Patrick,
Got it. I will try it this evening. I assume based on Gary's comment that I should not be using the test light in series?

From my rudimentary schematic reading skills, it looks like by disconnecting the ignition light the VR has been eliminated as a potential root cause (or at least not the only cause) given the fuse still blows? Given that the pink wire takes the fuel sender out, it could only be the fuel gauge, heater, or wipers (or wiring between those)?

Evan

[patrickt]

Correct. You do not use the test light in series, but you could have it tapping off the hot side of Fuse #3 and the other lead of the light going straight to ground. That would be fine.

You are also correct that by removing the pink wire from the fuel sender and the wires from the charging light (and the 10 ohm shunt) that you have eliminated the fuel sender, charging light, and voltage regulator from the equation.

What's left is the wiper motor and switch, tachometer, fuel gauge, and heater and switch, along with the wiring and plugs that connect it all. You have a 10v Smiths voltage supply under there too. We won't forget that.