Charging Problem - SC

[VincentVega]

Hello All

My 1981 SC is giving me fits, any help is much appreciated. One night the car lost power and died. I jump started it to get home. I tested my battery, checked out ok on a load testor. I just got back from a buddies shop who but his amp/load testor gadget up to it and he said there are no amps being put out. He suggested a wiring problem as the solution. I'm still reading through old posts and the wiring diagrams, but thought I would see if anyone has any thoughts.

Quick facts:

-Alternator replaced, new Porsche, ~6k miles ago
-Battery Tested ok
-Battery light does not come on anymore, bulb tested ok
-Battery voltage is ~12.3 volts with the car on or off
-Ground strap at battery replaced ~1 yr ago
-Ground strap at tranny replaced ~2 yr ago, cleaned contacts this week

What's left?

Thanks!

Chris

[GB83SC]

Firts test the volts with the car on again, just to make sure the 1st test was right (any auto parts has the tool) if you are not getting sufficient juice than check the belt. From there the alternator connections at the rear have to be checked. I had a battery start problem that ended up being the light at the glovebox had been left on.
Good luck!

[VincentVega]

Thanks for the insight. I've tested the voltage at the battery with the car running a dozen times, I'm pretty sure of that reading. I havent started pulling fuses yet, but it's not a draw problem. Good idea though.

[SpeedracerIndy]

Does your alternator have an external voltage regulator? If so, that would be something to check. When the car is running the alternator should be putting out closer to 14 volts if I remember correctly.

[GB83SC]

Chris,
How loose is the alternator belt? it should only push in about 1/4 " with pressure at the center.

[Early_S_Man]

Chris,

No warning lamp illuminated when you turn ignition key on = no output from alternator, since the current to pre-energize the field magnets HAS to come through the warning lamp!

If your alternator warning lamp bulb is good, then you either have a worn brush problem inside the alternator -- not likely at 6000 miles, or a wiring problem on the Blue #61 terminal at the gauge, or at the 14-pin connector junction -- either side, or at the alternator (if an updated model with integral regulator) or at the regulator or alternator -- if still using an external regulaor.

The following diagram shows the SC charging circuit with external regulator:

[VincentVega]

Thanks for the help Warren, just what I needed. Looks like I have my work cut out for me. When the car initially broke down the battery light was on. Since then it's been out. I tested the bulb with 12 volts and it's fine. Next I'm going put a test light on the bulb socket.

Thanks too guys, everything helps! The belt is tight and the alternator has an internal regulator.

I've had the alternator in and out at least 4 times now. Anyone needs an alternator replaced, I can have one out in 15 minutes.

[marcesq]

Chris:

I would pull the 14 pin connector apart and clean and spread the pins ever so slightly and clean sockets as best you can. Add a little electric grease and see what happens.

Glad to know we have an alternator expert in the fold.

See on Sat.

[VincentVega]

Thanks Marc. This weekend cant come soon enough

[JC930]

Don't forget the ground strap on the back of the alt.
jc930