1970 Voltage regulator help

I am somewhat new here and just bought a 70 911t and am going through it. Noticed battery was kind of just thrown in there so I decided to put gauge on it and readings were low. Charged and it holds a little low at about 12.35 with no drop over night.

Anyway at start up light goes out as it should but reading at battery is barely above non running at 12.75 or so. When rev'd to about 25-3000 we get into 13.50 or so but at 4k readings get high at 15.5. When brought back to idle and warmed up it reads fine at 13.5. Does anybody know what RPM alt kicks in or is it producing at below or at idle? Not new to cars just Porsche and want to make sure there are no particular issues.

Is there any source for new or rebuilt factory regulator? Any good link on adjusting? It looks as new inside and out. Would rather do bolt in and drive not play with.

Any good source? I know of a/m adjustable and newer units just want to keep fairly stock.

Thanks

The Marchal VR is still available, it's expensive, but it looks stock.

That said, I don't think it's your VR or alternator, I think it's your cable connections first, and your batteries second, and the VR third.

Here's why I think so-- when you start the engine, the warning lamp goes out, which means you have equivalent voltage on either side of the warning lamp-- the same voltage coming from the "trio" diode in the alternator (except that in your Motorola/Marchal alternator, it's a single diode) as is present in the battery.

"Zero-ampere" RPM is usually pretty low, around 1000 rpm, that's high enough for the battery to begin to charge. If it's higher than that, that means the VR isn't sensing the lower voltage caused by greater current consumption by the CDI-- as the RPMs increase the amperage drawn by the ignition gets higher- and that will draw the system voltage down, and therefore the field voltage down, and therefore the alternator output down, and the VR is supposed to compensate for that and be closed for longer, increasing the battery voltage.

I would clean the battery cables and the voltage regulator contacts on the engine electrical console and bulb holder in the oil pressure gauge down to bright copper and repeat the test.

Good luck!

I disassembled and used contact cleaner on VR. I have already gone through sanding connections so all are good. I noticed with clean VR that it seams that alternator kicks on at about 1500 or so RPM and reached full at about 3k. Once it gets into those revs it stays at about 15.8 and then comes down into the high 13's at idle again. If I shut off and restart and do not touch pedal it will again be at about .30 higher than batt voltage.

I am used to older US stuff and know that certain alts depending on pulley config barely put power at idle regardless of batt condition.

Anyway bought new battery starting at t 12.65 and now it reacts the same but as expected charges at lower and within spec 15.5 at 3-5500RPM and then comes down to idle in the mid 13's. Again if restarted we are at about batt voltage or .030 higher. Headlights cut off almost 2.00?

I will buy an adjustable VR to play with it but I am satisfied at this point.

Thanks?? comments?