Electrical problems with my 99 4.3 ltr blazer. Charge rate has dropped from 14 volts to 12 volts maximum (Engine running fast idle, lights and rear window heater on or off), tonight the dash went crazy, warning lights flashing, gauges up and down. On stopping the car, engine running at idle voltage showed a drop to 11 volts and the engine stalled. I presume it is the battery or generator, but which? Urgent help needed as I am in the UK and will have to order parts.

 

If the battery is more then 3 years old I would suspect the battery
But be sure to check all electrical connections from the battery
Especially the grounds
Poor electrical connections can cause all kinds of havoc and can shorten the life of the battery and generator/alternator
and it is possible for a cable to go bad if it is heavily corroded inside the jacket.

 

alternator...

 

After some thought I would have to agree with Shawn, if it where the battery you probably wouldn't be able to get more then a start or two out of it.

 

Thanks for all your help, have charged the battery and it is holding charge at just over 12 volts, looked at the alternator on the vehicle in daylight, windings inside look blackened and there has been a slight scorching smell. Looks likely I will be putting in a new alternator, just getting one in the UK isn't so easy!
Adrian

 

Try a netsearch to see if any parts stores in the USA(Auto Zone,Advance Auto, Pep Boys, NAPA,J.C.Whitney) or perhaps GM themselves are being supplied alternators from the UK or Europe. Then maybe you can get your local parts store to special order it from them for you. Best of luck.

 

Replacement alternator now fitted, battery seems OK. Thanks to all those who offered advice.
Adrian

 

As a side effect of fitting the new alternator my dashboard lights now don't flicker, so if you have flickering dash lights watch out for your alternator dying.