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Stock Gauge Wiring

Posted: 25 May 2019 20:49
by jeffball610
I recently redid EVERY chassis wire in the car and replaced all connectors (except the ignition switch) with Deutsch connectors. In doing so, I've ensured that there is no corrosion in the wiring and that the connectors will not come loose or fade away in the sands of time. However, the one stock gauge I still have is the fuel gauge. It never really worked great to begin with, but it at least let me know when I was low on fuel.

After rewiring everything, it appears that I'm missing something with how the gauge works. I was under the impression that it needed the signal wire from the fuel sender and a power wire. For the life of me, I can't seem to figure out which wire goes where on the stock pin out. I tried connecting wires like the stock connector, but it's still not working. Does anyone have a diagram that shows which each pin does? I can probably figure it out if I stare at it long enough, but I'd rather take the shortcut and use other people's knowledge.

Re: Stock Gauge Wiring

Posted: 25 May 2019 21:13
by datzenmike
12v is fed to a voltage regulator that reduces it to about 8 volts. This 8 volts is steady and does not vary from engine off non charge 12.6v to idle to full charging at 14.4v so the gauges read steady. The regulator is just a bi-metallic strip with contact points on one end and a coil of wire around it. When turned on the coil heats up the strip and it bends, opening the points. It cools and relaxes back and the points make contact again and this repeats. The voltage regulator powers the temperature and the fuel gauge so if one is not working it can't be the regulator. If both are not working it could be the regulator or fuse.

The temperature and the fuel gauge 'senders' are simply a path to ground that is variable. The fuel gauge resistance varies between 80 and 10 ohms. The lower the resistance the higher the reading. A full tank would be 10 ohms or less, empty would be 80 or more ohms.

If your fuel gauge works but the temperature gauge does not, ground the wire to the temp gauge and it should read full HOT. If it does then the sender' or the connection is at fault. If still no reading then the gauge or the wire from the sender is at fault.

If your temp gauge works but your fuel gauge does not, ground the wire to the gas tank 'sender' and it should read FULL. If it does then the sender may be stuck, bad or the tank is not grounded properly. If the gauge does not read FULL then the gauge or the wire to it may be bad.

Re: Stock Gauge Wiring

Posted: 29 May 2019 16:48
by jeffball610
I found the answer to my question in Dime Quarterly. Unfortunately, I had to use the "old school" paper version since the PDF on Google Drive is missing Volume 3 Issue 2. I had my wires right anyway, but I put the signal wire from the fuel sender on the wrong pin when I rewired the car.

Sidenote: Why does the stock 510 rear harness go down the driver's side, then across to the passenger side? I rewired it all with Duetsche connectors and ran the whole harness down the driver's side.