I was driving last nite.....i had my running lights on and then all of a sudden my tach drops to zero....i step on the gas and the needle pops back up again...i drove this morning and it was fine(no lights on)...... wat could this be???? i have a system with two amps and i have those aem tru power pulleys on my alternator...

 

this happen to me it was the alternator and a other time it happen to me a wire that goes to the alternator was loose and i have obx power pulley kit

 

wat did u do to fix it....new alternator?? took off the pulley???

 

yes new alternator

 

yeah got it rebuild but im sure the pulley are to blame

 

Before you buy a new alternator, you should check to see if your current alternator is supplying around 14.4 volts to the battery. First test the point on the battery while the car is running and it should read around 14.4 volts on the ohmmeter. If it reads around 12 volts at the battery terminal, then either your alternator is bad or there is a loose wire like what abexh22 said. Check the voltage output on your alternator terminals to see if it reads around 14.4 volts. If it doesnt, then your alternator is bad. If it does read around 14.4 volts, then you have a loose wire. I had a problem with my alternator wire (the one with the huge cap) coming off so i stuck a piece of a rubber band in between the gap and it hasnt came of ever since. Avoid driving around until you get it fixed because when i had the same problem, a friend of mine was driving behind and he noticed small bursts of flames coming out of my exhaust while my electrical system was dying; caused by the build up of fuel in the cyclinders due to low or no spark at all and then suddenly igniting.