Well, today when I came outside to go for a spin, the car wouldn't start - dead battery. I figured I must have just left the parking lights or something similar on when I parked and forgot about them.

No problem, I'll just jump it, then drive around for a bit. Well, my girlfriend comes over, I jump the car, disconnect the cables, and all seems well. The voltage seems at a solid 13.6 volts or so (NA S4) and I proceed to drive around charging.

I come upon a pretty steep downhill grade and double clutch down a couple gears (I believe bringing RPMs up to about 5k or so). Soon after, the lights all begin to dim and the car begins to die. I attempt to crawl home but the car completely goes.

After getting a ride and picking up her car again we go get her car again and I jump it again, let the car idle while connected. At this point the volt meter is reading a max of 12 volts. I try disconnecting the cable and sure enough, the lights dim.

So, do you think my alternator is dead? I've heard alternators may work extra hard to when a battery's charge is low, could I have killed mine with the *high* revs? What else could be bad, if not the alternator? Also, will I need to buy a remanufactured alt or would a used unit off of another na S4 be fine?

Motor is bone stock with the exception of a voltage stabilizer/ground kit. Definitely not the source of parasitic loss!

 

A used one should work ...if it's any good.

Make sure the small plug is attached to your series four alternator. It is a series four alternator, right? Or a ??

You might take it to a auto store and ask them to check your present alternator. I hear they do it for free. I don't know that for a fact.

Your best advised to never remove the batt terminal while the engine is running. That can (I said CAN, as in possibly) ruin an alternator.

If the small plug is on the alternator and engine idling, you should put your meter on the large output terminal of the alternator to see what it's putting out. Should be 14 plus volts.

As stated in the free online ENGINE ELECTRICAL seciton of the FSM, you put the key to ON, engien OFF, then backprobe the WHITE/black wire on the small alternator plug with the plug connected to the engine. The reading should be 1-3vdc approx. IF it read higher, the regulator in the alternator is kaput.

If things were Kosher on your car, the when you put the key to ON, engine OFF, the warning lights should all come on. IF not, the that is a sign that something is wrong. Unfortunatly the wrong could be just bad solder joints on the warning light assy.

But if that assy is good, the the lack of all lights coming on would indicate a bad alternator because a good one would output a gnd signal to a alternator relay in the CPU, which in turn would put a gnd on the warning lights to make them come on.

You might put a fully charged battery in the car and do the 1-3vdc thing mentioned. Whatever.

And or to check the warning light assy, you could remove the small plug from the alternator. Then, if you can determine a white/black wire from a black/white wire, then go put the WHITE/BLACK wire to ground with the key to ON. You should hear the alternator relay click and the warning lights all come on if you do that. IF it happens,then you know the warning light assy and relay are all good.

Or another way is to pull the small plug off with the key to ON. IF you have batt voltage on the WHITE/BLACK wire, then don't worry about the relay in the CPU or warning light assy. Alls well for the alternators field getting juiced up on start up.

So do the 1-3vdc thing first. Other things later.

 

Thanks for the advice. Yeah, I was thinking about just taking it to an autoparts store to have them test the alt but the car won't move. Looks like I'll have to buy a battery and just move it first of all.

Yes, na s4 and thanks again. The cars only got 67k on her so its a bit frustrating but then again, still is 21 years old haha.

 

yep advance auto will test your battery(to see if it has a dead cell) and your charging system when you bring the car oveer FREE(oneof the few things in this world)

 

I had the same problem a while ago.. and it died on my way to work.. i thought it was my battery as well. Turned out to be just the bolt on the alternator came loose.. after i tightened it back up, car started right up..

 

I am praying its a bolt but I do recall an electrical burning smell coming through the heater shortly before it died

Yeah I know autoparts stores will test it for free (along with a few other things) but the car is dead where it sits. Looks like I'll just be buying a battery and working from there.

 

or just take the battery over to the store and get it charged maybe alternater. i dunno i would like to save 80 bucks when my battery is fine ya know. charge the battery take it over test charging system and go from there.

 

I'm silly - its was just a the belt slipping majorly. Of course I didn't discover this until I bought a reman alt for ~$60 though. Thanks for the help, problem resolved! :P