delawaredave

1999 Mustang, V6. Battery light came on. Took off alternator - took to Pep Boys - confirmed bad - bought new alternator - installed.

Battery light still on - is there any "reset" that needs to happen ? Or do I still have a problem ?

The alternator is outputting close to 14 Volts. The gague on the dash shows charging.

My neighbor has a code reader - but he's away for a couple days.

Thanks !

socalwrench

14v charging volts is fine. The charging light could be reading the BATTERY voltage- which could still be low. Turn OFF the engine and read the voltage at the battery. If the alternator was failed for a long time- than there's a good chance your battery is undercharged.

Also, as far as clearing codes or resetting the PCM- simply removing your negative battery cable for ~15 min will do the job. Some cars can be more longer to clear, but the same principle applies. Please be aware that the adaptive strategy will also be cleared, so your car may run a little differently for the first 10-20 miles.

delawaredave

The battery voltage with car off is 12.5 volts -- so battery is fully charged (I put it on a trickle charger overnight).

Battery light is still on.

Should I remove battery cable and clear the codes and see if that does it ? Or should I leave codes in system and wait until neighbor gets back with code reader ?

I'd rather try clearing codes now - but I do not want to lose good information.

I also do not want to fry the new alternator. Thanks for your help !

socalwrench

Well, it's no problem really- I just have some time to hang out on the forums.

12.5v should be sufficient (charging it overnight was good; as most people forget).

If it were me- I would reset it. If there's still a problem, than the code will occur again.

delawaredave

I reset the computer - took negative terminal off battery for 15 minutes (correct ?).

Battery light is still unfortunately still on. Terminals to battery are clean and tight.

Any ideas ?

delawaredave

It is negative terminal that comes off - right ? Not positive ?

socalwrench

Removing either cable will cut the circuit and remove power. However, using the negative battery cable reduces the tendency for electrical spikes to occur.

Is there an engine light on? Just the battery light being on may not mean there's a code.

I wonder if there's a problem with the wiring on the back of the alternator. How many wires are there- not including the charging wire?

delawaredave

I re-seated the connectors, started the car - and now the battery light is off. Who knows. Maybe OK now.

Here's link to wires going into alternator (plus the red charging wire in back).
http://s295.photobucket.com/albums/m...t=DSCN3068.jpg

Thanks for your help !

socalwrench

You're more than welcome.

BTW, that's a very nice picture- I can even make out the numbers below the wires. Since, it seems to be working fine, I am going to stop monitoring this thread. But, if you have more trouble, feel free to send me a message or email me at grhperformance@yahoo.com.