Continuity?

[69/70Plymies]

I have a 1970 Plymouth B-body standard dash. With the voltage limiter removed, should there be continuity at the posts for the fuel gauge? With the wires disconnected, should there be continuity across the ammeter? Thank you.

 

[BLK 68 R/T]

Yes and yes. If you do not have continuity then it would mean the gauge is open internally and therefore defective.

 

[69/70Plymies]

With the instrument panel out of the car is there a way to test the fuel gauge and see if it is good. If there is continuity, does that mean it's good?

 

[Yatzee]

The voltage limiter does just that, limit voltage from 12V down to around 4.5. If you by pass the sending unit and go directly to ground, at the rear of the car, the needle will go to the very top. It's the resistance created by the resister built into the sending unit which varies the voltage through the gauge as the float arm raises and lowers. In essence the sending unit varies the voltage going through the coil in the fuel gauge and moves the needle proportionally. If you start with a 1 1/2 volt flashlight battery wired across the terminals of the fuel gauge, you will see the needle move to a set position for that voltage. As you add more batteries in series the needle moves proportionally with the increase in voltage. I am not exactly sure what voltage range your gauge operates at but you can find out by stacking batteries and when you hit the upper range of the voltage the gauge will read full and you will know the exact upper voltage the gauge requires to read full.

 

[BLK 68 R/T]

The voltage limiter does just that, limit voltage from 12V down to around 4.5. If you by pass the sending unit and go directly to ground, at the rear of the car, the needle will go to the very top. It's the resistance created by the resister built into the sending unit which varies the voltage through the gauge as the float arm raises and lowers. In essence the sending unit varies the voltage going through the coil in the fuel gauge and moves the needle proportionally. If you start with a 1 1/2 volt flashlight battery wired across the terminals of the fuel gauge, you will see the needle move to a set position for that voltage. As you add more batteries in series the needle moves proportionally with the increase in voltage. I am not exactly sure what voltage range your gauge operates at but you can find out by stacking batteries and when you hit the upper range of the voltage the gauge will read full and you will know the exact upper voltage the gauge requires to read full.

If you wire 2 AA batteries in series and then touch the + and - to each post it should read roughly half IIRC. Just make sure you don't go over 5 vdc, that is the purpose of the voltage limiter, to keep everything at 5 volts so you don't burn up the gauges.

 

[Glenwood]

here's an interesting article you may find helpful.

http://www.chargersourceguide.com/voltagelimiter.html