Help, Found unknown plug!!!

[Porscheman912]

I just got down installing an 81 3.0 into an 82 911. Over by the relay board there is a plug that I could not find the mate to. The plug is 3 wire, blue, brown and black. They look like they are for a volt reg, but the alt has a Valeo alt with it built in. When I got the car started, the batt light was on, can anyone tell me if there is a plug, or do I need to change things. The wiring on this engine was for the 81 engine, and I am not sure about the alt, whether it was in the 82 or 81. Engine runs great, on a new rebuild.

Thank you for any help

[syncroid]

If the new motor you installed has the Valeo internally regulated alternator there should not be an issue. Its quite possible your new motor has a bad alternator and is not charging. Start the motor and put a volt meter on the battery while running. You should be seeing approximately 13.75 to 14.25 volts. If less (like approx. 12 volts or less) then there is your answer.

[Porscheman912]

I know the alt is good, because I loaned it to a buddy who was working on an 81 with a bad alt, and mine worked find 2 weeks ago. I wonder if the ground strap off the block has a bad conection, I did paint the fan and housing. I will check with a mutimeter in the morning and see what it is doing. The batt light is on.
Thank you

[syncroid]

Welcome. Here to help.

[Porscheman912]

I have been out in the hot sun all day, my mind has gone blank. I am just happy to hear this thing run after a few years of having it.

[Porscheman912]

Well, it turned out being a bad ground. I cleaned a spot off, put it back together today, and now the light is out. Thank you very much for the help.