Anybody know about this crazy (charging system light ) comes on intermittently - once and a while - replaced the alternator with a ebay special in march could I be bad already ? checked with volt meter shows o.k. 13.8 volts and gauge shows o.k. too. don't know about this one, another electrical mystery with this 05 mustang v-6. has anybody experienced this problem. thanks Pat..

 

You get what you pay for in most cases. Take it to an auto-zone or comparable auto parts store that check your charging system for free and Under a load. Or, take it off the car and have it bench tested.

The intermittent could be a voltage regulator issue that only happens under high heat or a load. On car test under load will help see if that's a problem. Bench test may or may not see it.

 

FWIW, haven't purchased one myself, but, I'm seeing ads, and seen one at local auto parts stores, for instruments that you plug into your car and it sends a full lanquage "what's wrong" versus just a code.


anybody have a story to tell about those yet? Or a recommendation?

 

Not relevant to this thread. In short those only read OBDII codes and provide additional information that you would find by having a regular OBDII Scanner and Googling. They have nothing to do with checking or cooling system lights unless they are related to an OBDII code. Companies have done a great job of marketing them on Facebook where the masses are fairly clueless about cars in general.

 

The best way to see the voltage, is at the battery terminals when the car is running.
Check idle, and at 2000 RPM. Should see 14.4 at 2000 RPM, optimally.

AMPs, determines the charge rate of the battery, and that's a different test.

Also, you have some parasitic drain at the battery, so even if you charge okay,
and come back later and the voltage is below 12, you can check for parasitic
drains. Car off, disconnect the + terminal, set on something to insulate it from
the body of the car. Use alligator clips, and clip the positive lead of the tester
to the + post on the battery, and clip the COM(-) lead of the tester to the cable
head. This will show amps being drawn from the car when it is off. You should
not be above 40mA when the car finally goes to sleep/rest mode. When you
clip the - lead to the terminal head, you will wake the car up, and the drain
will be higher for about 8 minutes or less. Most meters can handle up to
a full 10 amp load. If the fuse pops in the meter when you hook it all up,
then the draw is very Very bad...

A full option GM vehicle can experience a parasitic load of 25-35 mA, so you
should not be seeing a high drain.