how to check alternator in 993
 

I was just wondering if there is an easy way to see if the alternator is charging on my wife's 95' 993. The other morning I tried starting it and the battery was dead. The battery should be about 2-1/2 years old. It almost never get's driven in the winter but I took it out a couple of times and the battery was dead a couple of days later. I just want to know if the battery is dead or if the car is not charging.

Thanks
Oscar

Run a voltmeter on the battery terminals while the engine is running . Should read 12.5 and above 13v - 14v is normal. Less than 12v your alt. is dead.

Get the car running and put a voltmeter across the battery.
A good alternator will put out between 13 and 14 volts.

Another way is to jump start and let engine idle and turn everything electrical on. If it stalls after a while then probably alternator. If not turn everything off and drive round the block. When you get back turn off and try to restart. If it starts the alternator is good and the battery is probably losing its charge over time.

The best way to check any alternator is to find an oscilloscope. If you have a dropped or weak diode, it may not show up with the voltmeter test. An oscilloscope will show you the ripple and any deviations from a normal ripple can easily be diagnosed with several good web references.

Actually, 14.4 volts is typical for most alternators in good shape, but anything over 14v is fine. between 13.5-14 is ok at at idle, but the voltage should rise with the RPMs then level off at some point around 2500-3000. Make sure to turn on all electrical stuff such as AC, rear defroster, headlights. Under 13.5 is marginal (I'd say not good, really) especially if the car's accesories are off.

Edward