TR4/4A TR4 FUEL GAUGE CONVERSION FOR A TR3

My dash fuel gauge on my 59 TR3 quit working (after I took it apart and cleaned it up (oops)). The tank gauge works fine and gives me variable resistance depending on where the float is. I purchased what I "thought" was a TR3 replacement gauge that works, but it is for a TR4 and not a TR3 and it gives me readings that are way too high. My old original gauge is Jaeger FG2530/20 and my new one is Jaeger BF2206/00. What I am wondering is can I place the proper resistor between my tank and gauge that will make it work properly? Has anyone done this before? Thanks ..................AL

Alvin, who did you buy the incorrect one from?

Nope, can't be done. The TR4 sender and gauge work 'backwards' to the TR3. The TR4 gauge reads "full" for (nearly) zero resistance, while the resistance of the TR3 sender goes up when the tank is full.

You could possibly build a little electronic circuit that would translate, but it seems a lot simpler to find the correct gauge.

BTW, the TR4 gauge is sensitive to charging system voltage, so you'll also need a voltage regulator/stabilizer to make it work properly.

Thanks Randall. Guess I have to scrap that idea........but it "seemed so brilliant"! I bought the gauge on E-bay and I will resell it. It is a nice gauge.

I ended with a TR4 fuel gauge for my TR3 too. I had trouble getting the proper sending unit for the gauge, and gave up after several obvious incorrect attempts.
(Gauge number BF 2301/00)

Since I already have the voltage stabilizer for the temperature gauge, I opted to find a suitable sending unit. I plan to use a SunPro 'universal' CP7583 fuel level tank sender. I had to swap the tank mounting plate with the original one, but the float arm was adjustable, and the resistance is close to what it should be. Empty shows empty, and full shows full -the accuracy of the rest isn't that important to me. I can't tell how well it works in practice, until the car is finally on the road. But the float at the bottom of the tank says empty, and at the top shows full.

My notes say TR3 empty=2ohms full=85ohms TR4 empty=240ohms full=30ohms.

Hope this helps.