Voltage Regulator Grounding Battery

[mikedren]

I've been having an issue with my 1972 bug lately where if it's left to sit for ~3 days, I can't start it up. It's still got a little juice, but not enough to crank it over. I've tried to test for voltage draw at the fuse box and also at the battery. When all of my fuses are disconnected, I'm still getting a voltage draw. I then disconnected all of the wires from the voltage regulator one at a time and found that when all wires but the one connected to the battery were disconnected, I'm still getting a voltage draw.

So my question is, is this supposed to happen? I'm assuming not. I've made sure that the voltage regulator body is grounded well (per some manual I think), but I don't think it's supposed to have any current passing though it in that manner, especially when it's not connected to anything but the battery. Before I went out and got a new voltage regulator, I wanted to make sure it was bad. Thanks.

[Marc]

Alternators were first introduced in mid`73 - first in Convertibles, then in Supers, finally in Standards (and they were never 2-wire back then, they were all externally regulated until late in `74).

Generator regulators have a "cut-in" relay that divorces the generator from the car's electrical system below a certain RPM, specifically to prevent the problem that Mike's having.

Old-style electromechanical regulators are no longer available for 12V 30A (SR15X) generators, but there's a modern electronic version you can still get:
http://www2.cip1.com/ProductDetails.asp ... D350%2D068

[mikedren]

Thanks for the background. I do have the old style generator (probably should switch to the alternator). So I'm assuming your saying that my voltage regulator is bad? I'm guessing it shouldn't work like that, grounding out and causing a current.

[Marc]

Yes, with the cut-in (A.K.A. "cut-out") contacts stuck shut, whenever the engine's off the generator is trying to act as a motor, heating it up and discharging the battery. Until it's fixed you need to pull the negative battery cable whenever parking the car.
To convert to alternator you'll need a different pedestal and most likely different accelerator pump linkage on the 34PICT-3 carburetor (it was modified/inverted on later versions of the carb to clear the larger diameter of the alternator housing). Modern alternators are all of the internally-regulated style so no regulator would be needed; you just need to make some simple wiring modifications under the back seat. Get an 11.3x912 belt, too - although the pulley and 9.5x905 belt from a generator will fit, the thicker belt is needed to resist slippage under the higher load presented by the alternator.

[mikedren]

I'll definitely check that out. Part of me doesn't think that's it as the voltage drop is happening when no other wires are connected to the voltage regulator other than the one from/to the battery. The generator was not connected to the voltage regulator when I was testing it. (That's still possibly a problem though) Hooking it up that way would eliminate the generator from the test, correct? Thanks for all the help.

[Marc]

Correct, if the D+ & DF wires to the generator aren't connected then there must a low-resistance path to ground inside the regulator causing the battery to discharge. Check that nothing conductive has slipped down between the regulator and the body, there are exposed resistors there on the OEM-style regulators.