So. I start up the ride today, put the roof down, take a look at my dash and the check gauges light is on. At first i thought it was going to be a beautiful day.... so i was driving down the road and noticed that the batt. gauge was dropping below 13 pretty quick. i had the battery checked, and of course it was dead. i replace the batt. and had the alternator checked. the alternator was reading just above 12.v the check gauges light was still on, and the batt. gauge was still below 13. is it the alternator? i've changed one before, but not with a serpentine belt, is there any thing special i should know?
Thanks in advance
p.s. 1999 3800

 

Try starting it up, run a few minutes, pull the positive terminal off and if it stalls, it's most likley the altenator.

 

Don't forget to pray that the computer survives that old school test. They don't take kindly to voltage spikes, they like steady consistant powerflow

 

[X(] please dont try the old school test remember these cars are run with electronics and they reeeeeaaaallly dont like it when large spikes are created and electricity has no place to go. if the alternator isnt producing at least 14 volts and the volt gauge only shows 12 or so or less then your running on the battery. now there can be fusible link, wiring or connection problems but most likely its an alternator. the alternator wheather on the car or test bench should produce AT LEAST 14 volts if not its time to get a new one kurt

 

If the voltage is staying low you either have bad alternator or an internally shorted battery. Chances are the alternator is sick, especially if it is making a whining noise (bad diode/s). Not a good idea to run the engine with the battery disconnected, as the alternator looses control reference and can spike, and with nothing do absorb the spike, electronic equipment, including the computer can be damaged.

 

thanks for all of the input.
i was reading up on this and foung reference to belt tension, and also that there is a tool to measure does anyone know what the tension is?

 

[X(] most if not all gm cars use a spring tensioner for belt tension and is not adjustable. the spring can go bad but havnt seen it that often. is the belt squealing like its loose?? alternators arent designed to produce proper voltage or amperage at idle to 1000 rpm's so make sure the engine speed is up above this when reading voltage. there are tools to measure belt tension but due to the compactness of todays engine compartments they dont fit very many places. belt deflection specs and or adjustment procedures (if its manually adjustable) can be found in service manuals kurt

 

what an easy job.
took 20 min.