S4 TII
S4 ECU
S4 CPU
S4 harness
S5 engine
S5 alternator.

The charge light keeps coming on and its verrrry annoying. The fsm shows that the CPU turns the charge light on but i cant find anywhere that shows the condition. The alternator is at 14.2v with the e-fan off and 13.9v with it on high at idle. The S4 FSM says normal condition is 14.4v - 15.0v and the S5 FSM says normal is 14.1v - 14.7v.

How do i get this thing to shutup or work normal? Heres a picture of how the alternator is hooked up (i didnt hook it up).

 

On a normal series four, the WHITE/BLACK wire on the back of the alternator will output a GROUND signal to the alt relay inside the CPU which in turn causes all the idiot lights to come on.

Once the alternator puts out, that gnd signal disappears and the relay in the CPU relaxes and the idiot lights go out.

I think you seem to have one terminal on the back of the alt going to a constant 12vdc source for the internal regulator. And that's good. The OTHER blade terminal on the back of the ECU would be going to the WHITE/BLACK wire in the alternators small plug. Is that the way you have things?

The volage you stated won't cause the light to come on. You've good voltage. It's gotta be something to do with the WHITE/BLACK wire.

Answer this. Which blade on the alternators jack do you have 12vdc constant voltage going to? Say your looking from the back of the alternator to the front of the car. Is the constant 12vdc going to the blade to the left or to the right?

 

terminal S goes to the battery.
terminal L goes to the harness (where L used to go on the S4 alt)

 

seems like its hooked up right from what you said hailers. all the idiot lights go out but the charge light comes on like 10 seconds or so after you start the car. i forgot to mention that the second to last time i drove the car that charge light was on but i had to drive it home so as soon as i put it in reverse and backed up 20 feet it shut off and never came back on. last night this didnt happen though.

 

Actually..........I've no idea at all why that light is coming on. Anybody know?

 

Okay, something fishy here.

Is it just the charge light?

Its not the majority of the idiot lights?

Because if it is just the charge light, then you have either a bad idiot light cluster or the wrong idiot light cluster.

 

ok lol, i have no idea what happened but i tightened the alternator belt and the connectors but didnt change a thing and the light went out. the light was out when i bought the car too, it seems like an intermittent thing. also something weird was happening when i had the key in the on position (not always happening though). the lights would come on and stay on with the key in accessory (engine off) then a buzzer would come on and not shutup until u started the car, then all the lights would go off. if it happens again ill take a video of it. i also jiggled the cpu harness where it connects to the cpu. maybe i need to resolder it. i still dont get how the charge light works. i wish their were better schematics.

 

Again I ask:

Is it just the charge light?

 

yes it was just the charge light. now its off though. i replaced the fuse for the cooling fan circuit cause it was bad and now i have a cooling fan light stuck on hah.

 

Then you probably have the incorrect idiot light panel for the dash harness.

See the ground needed for a S4 charge light comes from the CPU... and it lights almost all the idiot lights.