Stewart-Warner Fuel Gauge Connections

[GrowleyMonster]

So, my old but new to me Bruce Roberts has a lot of gauges that are not working or not connected and I want to get them all working, starting with my fuel tank level gauge. I have no way to sound the tank. It is a long, narrow, not very tall tank, surveyor says 14gal but looks like about 10gal to me. I have a jug catching overflow from the vent so I know when it is full. There is a level sending unit. The tank is aluminum, and grounded. There is a wire connected to the center terminal of the sending unit. I followed it to the fuel level gauge in question. It is the only wire connected to the gauge, the red wire.

There is also a push-pull knob switch right next to each gauge. I am assuming it is for power to the gauge or maybe just to the light. Not connected. THere are a bunch of fuse holders nearby, some connected to random wires going who the hell knows where.

Am I correct in assuming that I need to get 12v to the other bottom terminal, and ground the gauge with the terminal under where it is marked "GND"?

I am assuming that the sensor is just a variable resistor with a float arm. Is this probably correct? What resistance should I see for max and minimum fuel levels?

Don't worry, I got a lot more gauges to connect! One at a time. I think my oil pressure gauge is working... but it is always either zero, (not running) or 40psi (running, any speed, in gear or neutral). I guess there is a bypass or something, There is a voltmeter that seems to be stuck on 12.6v or so, no matter what, even during engine start. Engine temp gauge not connected, and obviously I want to get that working. Charging amps ammeter not conected. Tach not connected. Engine is a Westerbeast 4-107, probably pulled from a Morgan in the late 70's, runs great but I need to get some gauges hooked up to it cause I can't afford to burn it up.

Also if anybody has any sources and part numbers for the lamp holder and the correct bulb for these gauges, I would certainly appreciate it.

[ranger58sb]

Originally Posted by GrowleyMonster

There is a wire connected to the center terminal of the sending unit. I followed it to the fuel level gauge in question. It is the only wire connected to the gauge, the red wire.

Am I correct in assuming that I need to get 12v to the other bottom terminal, and ground the gauge with the terminal under where it is marked "GND"?

I am assuming that the sensor is just a variable resistor with a float arm. Is this probably correct? What resistance should I see for max and minimum fuel levels?

At one time, our fuel sensor (original, i think) was a Stewart-Warner with a float arm contraption... and sounds like your description. An old pic shows probably signal on the center terminal on the "lid," (cap, with 5-hole SAE pattern mounts to the tank body) and maybe ground on a tab over to the side of the "lid."

FWIW, I replaced it with a WEMA/KUS SSS sender, a straight tube with an float... and I eventually also replaced the gauge with a CruzPro digital gauge. My schematic shows signal from the sender, and power from the nearby buss, or ignition circuit. IOW, maybe only one wire all the way from sender to gauge, and a ground to somewhere, could be correct.

(The WEMA/KUS sender eliminates all that hokey float arm mess.)

The SW and WEMA senders were both "standard" resistance, IIRC 33-240 Ohms (Full-Empty), but 180-10 is another common resistance standard. Our original analog Faria gauge was designed for the 33-240, whereas the CruzPro offered several selections, including 33-240 and 180-10.

I think I remember being able to measure resistance at the sender to get a feel for whatever the likely resistance range might be.

The third screw mount on your SW gauge might be for both power and maybe also back-lighting. Just a guess...

-Chris