running new wiring for gas gauge

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In an attempt to get a working gas gauge on my 1993 Starcraft 240 Starfish pontoon boat, I've checked out the sending unit and gas guage as described in my previous thread http://forums.iboats.com/showthread.php?t=307300

I've purchased a NOS gas guage, a new sending unit and got new wire. I installed the gas gauge and the new sending unit ( seperately , checking for correct operation before trying the other unit). Still no reading. ( all electric work has been done with battery ground disconnected )

At the sending unit, the center wire is red and the ground is black & green. The green goes directly to the metal side panel of the boat from the sending unit itself. The red and black wires run to the console.

Due to Starcraft's twisting of the wireloom and placement over the tubes, I can not physically pull the wires out to visually follow them.

I ran new red and black wires from the sending unit up to the console. Looking at the back of the gas guage, I have reddish/pink wire for the sending unit wire, black wire at the center post and a purple wire to the other side with a pigtail for the 1/4" male plug for the lights.

Here's the question

To wire this direct --
Am I correct in assuming the sending unit wire ( red) goes to the post marked "sending unit", the black wire to the center post and leave the factory purple wire in place?

This would assume that the purple wire would power the sending unit ( right? )


Thank you
Jeff ( who's figuring out nothing is as simple as it should be )

Re: running new wiring for gas gauge

Here's the diagram. But why run a black (ground) wire all the way from the back of the boat to the front? Ground is all over under the console and that terminal on the gauge can be connected to the ground terminal on any other gauge or to the ground buss on the fuse/breaker panel. Waste of wire. The ground wire to the hull "electrically bonds" the tank sender to the hull. If you are getting no reading you need to trouble shoot rather than rewire. With the key in the RUN position, you need 12 volts on the "I" terminal of the gauge. You use an Ohm meter to make sure you have continuity between the GND terminal on the gauge and battery ground. If you have continuity between the "S" terminal on the gauge and the sender, the system should work.

Re: running new wiring for gas gauge

Here's what I did today.

Checked new sending unit for continuity. With the wires disconnected, I got a reading of 125.5 to 125.8 ohms. ( the old unit fluctuated between 116 and 148 ohms)

Checked continuity between the ground on the gauge and the ground block on the inside of the console. That was good.

I checked the continuity of the red sending unit wire from where it would connect to the guage to where it connects to the sending unit. That was good.

I got 13.2 VDC between the "I" terminal on the guage and the negative post on the guage with the key in the "ON" position. ( all the gauges light up but no reading on the gas guage)

I did run a jumper wire from the back of the negative post on the guage to my meter and then having the meter set on VDC, touched the main body of the sending unit. I got a reading of 13.2 VDC

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I guess all that's left is tracing the black wire and checking that for continuity. Am I correct in assuming that once I find which wire it is, disconnect the battery, turn the key "ON" and check for continuity?

Thanks for the help
Jeff

Re: running new wiring for gas gauge

If the black wire is a ground wire it should not be switched so it is of no consequence if the key is on or off. Ground is ground -- there are no switches in that circuit. Use the ohms (resistance scale) to check any length of wire (unpowered as the meter uses its own power source). The diagram I previously showed is as simple as I can make it. You either have that configuration or you don't. The only connection not shown is the "bonding" between the shell of the sender and the hull of the boat. The gauge would work even without that wire.