Bad voltage regulator

[Walker]

How can you tell if the volt. regulator in an S3 is going/gone bad? As soon as I turn the key to start the engine the #8 fuse blows. I don't even get to the full start position. Any help would be appreciated.
Art

[Nium]

If the voltage regulator for the alternator is bad the battery either doesn't charge or over charges.

If the voltage stabilizer for the fuel and temperature gauges is bad the gauges will read inaccurately.

If you have a fuse blowing then check for shorts. Probably a wire rubbed thru or routed thru a hole without a grommet where the sharp sheet metal has sliced through the insulation and is shorting it out. If you have done any work recently start the investigation there.

[Walker]

Thanks Nium. Haven't done any electrical work lately but the PO () mickey-moused a tow plug that is a freakin' mess. I'll start there and see where it leads.

Art

[Terrys]

If you want to rule out the alternator, simply disconnect the heavy brown wire from the back of fthe alternator, and turn the key on. Don't start it though, alternators shouldn't be run without being loaded.
However, the alternator, good or bad, shouldn't be blowing a switched hot line.

[SafeAirOne]

How can you tell if the volt. regulator in an S3 is going/gone bad? As soon as I turn the key to start the engine the #8 fuse blows. I don't even get to the full start position. Any help would be appreciated.
Art

It's not the voltage regulator. There is a short in the electrical system, downstream of the fuse, as others have mentioned.

What do you mean by "the #8 fuse"? There are only 4 factory fuses in the SIII. Looking at the schematic, do you mean the fuse between terminal 7 and 8? If so, the only FACTORY items powered off that fuse are the fuel and temp gauge systems and the brake light circuits. Who knows what a PO may have added.

Presuming it's the terminal 7 to 8 fuse you're referring to, you can narrow down the shorted circuit by removing the 2 green wires (and whatever other wires might have been added) from terminal 8, stick a new cheapo 10amp fuse in, then reconnect the green wires one at a time, noting which one blows the fuse.

NOTE: Don't use up all your spare 35amp original fuses, they're not regular 35 amp fuses that you can pick up at AutoZone.

This will tell you which circuit is the shorted one. After that, it's simply a matter of finding the spot where the power is errantly going to ground.