Hey I put a brand spanking new alternator on my 1990 firebird formula .. But it gets really hot and it put out 19 volts.. The original alternator surged and then i put a rebuilt alternator on it and it still ran hot, then i put the new one on and it was very hot and putting out 19 volts idk what to do

 

 

It sounds like the voltage regulator in the alternator is not doing its' job anymore. I would remove the battery and have a good parts store run it on their analyzer. Then, I would hook up the good battery in the car with the alt disconnected and measure the current draw on the battery...it should be very low near zero with nothing running. I would then start the car (don't worry about the starter draw on startup) with the alt disconnected and record current draw. Use different lights radio ect and see if something you turn on is a current hog. If all seems well maybe you just bought a junk alt (it is easy to do nowadays) I usually stick with new GM ones and have pretty good luck. I never buy electrical items from "big box stores". You will need a friend with a dc current clamp and Multi meter or an old engine analyzer with a calibrated shunt (comes with the analyzer) to measure high currents though. You may be able to use a standard Multimeter to measure the current...just not on startup...prepare to blow a meter fuse or two!!!