Electronic voltage regulator

I had to replace the voltage regulator on my MF 135 gas with the Perkins engine. I used an electronic voltage regulator. Everything worker fine except the fuel gauge. I have been told that the fuel gauge will not work when useing an electronic regulator but no one can tell me why. What do you say?

Thanks for your replies

I've changed 3 Oliver tractors to electronic regulators and the gauges work fine.

The 1800 still has it's generator. I had to change it to negative ground and I did have to modify the water heat and fuel gauge so they would work on negative ground. It's a touch tricky. I've looked at newer gauges and I don't think they can be switched.

That's the only reason I can think of that it might not work since I don't know what all you've done.

RT

A LONG time ago GM/Delco came up with the best alternator system that was out there at the time.

It had a mechanical voltage regulator with a "field relay" inside of it.

Massive Ferguson, Oil Allover, and others came up with some creative circuits to derive some other functions out of the field relay in the Delco 10DN mechanical voltage regulator above and beyond what was ever done in a GM vehicle.

Fast forward 40 or 50 years, and aftermarket suppliers have developed replacement solid-state regulators that can do the basic functions of the old mechanical regulators but cannot fulfill every possible permutation that creative folks eked out of the old mech regulators.

You either need to find a "NOS" mech regulator, or do a bit of rewiring to make everything well again.

I take that there is no "ignition switch", just a start button and a mechanical kill lever?

And that would be why the fuel gauge is (was) powered off the #4 terminal of the regulator.

And for whatever reason that terminal is not used with the electronic version or the regulator.

Just to verify this is the problem, start it up, rev it to initiate charge, see if there is 12v on #4 of the regulator. If no, that is the problem.

So, the object is to get switched (hot only when the engine is running) power to the wire that comes off the regulator harness #4 position.

Is there a wire from the R terminal on the alternator to #2 on the regulator? If so, use your test light or volt meter, see if that wire makes 12v with the engine running, 0v with it off. If there is no wire, check the R terminal on back of the alternator. Be sure to rev the engine enough to initiate charging.

If that is happening, you can power the gauge from that wire. Cut the wire from #4 of the regulator, move it to #2 or the R terminal of the alternator.

If that is not doable, as in no 12v at the R or #2, then it will be necessary to add a normally open oil pressure switch to power the fuel gauge. One side of the switch to a 12v power source, the other side to the fuel gauge wire, formerly powered from #4 of the regulator. Remove the wire from the regulator harness, do not back feed power into the regulator.

I also have a MF135 and have had to replace the original mechanical voltage regulator with an electronic one. The mechanical regulator had a resistor on the 4th terminal that cut the voltage to approximately 4 volts for the fuel gauge. You cannot just hook the fuel gauge to 12 volts as it will peg the gauge. The new electronic regulator leaves that resistor out. I simply got an adjustable potentiometer (0 - 10K) and put it in line from the 4th terminal to the gauge. Empty your fuel tank and fill it with 5 gallons which is half full and adjust the potentiometer until it reads half full. There are sites that sell the mechanical voltage regulator but they or $95. The potentiometer is way cheaper.