Bjeralds

iTrader: (1)

My alternator died in my S5. Buddy. Is selling me a bunch of parts for $100. Including an S4 alternator. All I have hooked up on the S4 is the main wire from the alternator to the battery. And my battery is dead so I have my jumper box hooked up.
As soon as I turn the key to the on position within 3 seconds it blows the main 100 amp fuse. I will get an S5 alternator probably this week. Just wanted to try to make this work so I can get back and forth to work.

Any ideas as to the cause?

Rx-7fetish

Your s4 alt with just the main power is sensing a dead battery and also has no ground. Instant blown fuse.
You might could look up the wiring diagrams on here for fitting the s5 into an s4 and reverse engineer it.

HAILERS2

It would be real hard for an alternator to not have a ground. The /regulator of any of these alternators gets its ground from the bond of the body of the alt to the engine via the attach bolts of the alternator.

Either the ouput cable is touching the body of the alt when you attach it to the alt or the guts/wiring internal to the alt is shorted to gnd and blowing the fuse. Remove the output cable and then see if the fuse still blows. Most likely your output cable is touching the alt body or ??? intercooler causing the blown fuse.

Bjeralds

iTrader: (1)

That's what I was thinking Hailers is that it pretty much has to be grounded if it's bolted up. But I believe you hit the nail on the head with the second part. With it disconnected no it does not blow a fuse. And the plastic spacer where the output cable is was missing. and without thinking i thought i'll just use a nut as a spacer. Which in turn grounded the output to the alternator thus blowing the fuse. Sounds like what happened don't you think? Gonna get some sort of rubber or plastic spacer and try again.

HAILERS2

-Remove the cable from the alt. Key to ON...................now offer the end of the cable up to the stud on the alt where it would normally bolt on. Just touch the end of the cable to the top thread on that stud on the alt.

If the fuse did not blow then it must be the way you bolted the output cable to the alternators stud i.e. the cable wire must have been touching some part other than the threaded stud alone.