Alternator not charging, battery and alternator are good.
 

Okay here is the run down. My inertia fuel switch in my maf sensor went bad in my fc causing me to burn up the starter. The wire from the starter to the solenoid was completely burnt. So I got a new starter and put it on, and also wired a 30 amp toggle to the fuel pump which is running off a 20 amp spare in the fuse block.

Well my problem now is that the alternator isnt charging the battery. both the battery and alternator are good. Even swapped out the alternator with a new working one, still happening. All grounds are secure.

Please help.

S4 or S5? NA or turbo? I can't tell you much about the fuel toggle, but I would say that's a good place to start. Have you attempted to do without the toggle since replacing the starter? Also did you replace the MAF? Because if you didn't, it's probably toast.

What is the voltage output of the alternator would be some important info to share. And how would a switch in the AFM burn out your starter??????????

Its a s4 non turbo 5 speed. i have the fuel pump toggled due to the maf not sending the signal to the fuel pump due to the fuel switch that isnt working thats inside the maf.

the voltage output isnt a steady voltage. after i jump the car it goes from 14 down to around 9 volts and its kind of a gradual decrease. but goes pretty fast.

Tried a new working alternator and it done the same thing so i ruled out the alternator.

Hmmm. Why not just replace the AFM and the MAF to start? I still don't understand why that would even remotely affect your starter, but if you know there is a problem in it, you need to replace it.

it didnt affect my starter. it went out so i wasnt getting fuel and didnt know it and kept cranking and burnt my starter up. im wondering if the maf would be drawing down the power or not.

You have a plug w/two wires that connects to the back of the alternator. Top wire is Black/White and the bottom wire is White/Black. Do you have this plug connected to the alternator? Are you sure the alternator pulley is at the proper tension, not too tight nor too loose? And the AFM will not affect the alternators output but the starter would. And jumpering the fuel check connector will bypass the broken fuel switch found inside the AFM so there is no reason to toggle the fuel pump at all.

well i didnt know if it would run correctly off of the plug if i jumpered it. it would be the same as grounding out the brown wire to the maf so i may try it and take the toggle off and put it on the signal wire so i can still cut the fuel when starting to prevent flooding.

the plug that went to the alternator looked burnt up so i cut the plug and put connectors on the wires and plugged em back up correctly on the alt. they arent touching each other either.

The two wires on the back must have the proper voltage and again, the B/W wire is on top and the W/B goes to the bottom pin and of course the wires need to be making a proper connection and perhaps maybe this is your problem. W/key to on both of these wires will have 12 volts w/the plug disconnected from the alternator. W/the plug connected the voltage on the W/B wire drops to 2 volts or so w/key to on while the B/W wire stays the same. W/the engine running both wires will have 12 volts to them. And make sure the large voltage output wire is mated properly to the alternator and w/the car running use this output wire to get an accurate voltage reading instead of relying on the voltage gauge in the instrument cluster.

Yeah the wires are showing correct voltage and are in the right spot. ill try jumping the plug once i get home from work and see if that helps. if not then i think i got a short somewhere. all my grounds are fine, secured and not dirty or anything.

The alternator will self excite itself if you rev the engine above 4 to 5k and if the voltage returns to normal levels then either the alternator is no good or the wiring is just not right. And alternators can test well outside of a car but not when installed and this occurs rather regularly w/cheap aftermarket replacements. One thing you can try is to disconnect the output wire from the alternator and read the output from the alternator terminal and see if there is a difference. And when replacing the starter are you certain you reconected it properly w/respect to the wiring that comes from the battery (positive and negative cables)?

I've tried to excite the alternator and it didnt work, and like I said before i swapped it out with a working one and it done the same thing. I reconnected everything properly when i put the starter on.

could it be a possibility that my battery is bad? or would that even effect the way the alternator works? Im not 100% on how the charging system works on the s4 fc's.

It might affect it, but if you disconnect the output wire from the alternator and test the alternator output from the alternator terminal that will tell you if the problem is caused by the alternator itself or some outside source.

ive tried with the output wire on and the voltage was decreasing the same amount as the battery.

With it off, with it off.

okay, ill try it.

With the output wire off it was showing 17volts while running

It should peak at 14.4 volts. Apparently the voltage regulator is not doing its job.

EDIT: You might want to reconnect the output wire then start the car up then disconnect the battery and then test the output of the alternator.

Thanks satch. I found the problem. If I take the ground terminal off it runs fine and charges. So I have aa bad ground.

Post a pic of that "ground terminal" will ya.

It has brand new terminals on it.

..and WHAT has brand new terminals on IT?..the harness,the battery cables,the alternator?
You say you took the ground terminal off and it runs OK now,So take a pic of the terminal you took off and post it.
I'm curious as to what you did and the only way to get that answered is with a pic.Your explanations..frankly lack any info.(sorry)..

The battery has brand new terminals on it. i took the negative terminal off of the battery while running and it ran fine.

would that mean i have a bad ground, my battery is shot, or what?