I have a junkyard CS-144 swapped into my Camaro. A few days ago I noticed that I'd get voltage spikes. Especially when the engine was cold. It seems like it always would happen when I like hit the blinker, or tapped the brake pedal. And when it would spike it would make my dash lights go bright and even made my tach needle jump. A few days after I started having this happen, my car left me stranded. It didn't have the amps to crank the starter. The batt read 12 volts, but couldn't turn it over. I got jumped and went straight to sears and got a new battery. With the new battery I don't have the problem. So...did the dead battery come from the voltage spikes? or were the voltage spikes because the battery was hashed and the alternator was having troubles working with it? I want to know if a new alternator is in order since it was pulled from the junkyard and I don't want to be stranded or mess up my new battery. Also with no load the voltmeter is on the line in between 13 and 18 volts. Is that too much?
Thanks

 

well i just replaced my moms alternator in her 89 astro van.. the voltage would spike when cold, warm, at idle, giving gas.. it didnt matter.. it still charged the battery enough to start it again..

 

Soo is the verdict to change the alternator? Anyway I can check if it is bad? I don't get the spikes anymore, but...

 

You had low or a bad battery. A good battery is essential for proper operation of the alt. you may just to have needed to trickle charge the old battery. with a high out alt the terminal voltage at the battery comes up almost instantly and since the regulator only looks at voltage it never charges the battery correctly. An alt is NOT a battery charger. Case in point my car. Did some engine work and forgot to close the hood after a couple of comforts . Battery(new) was dead as far as cranking was concerned. Jumped it with a porta-pack and after weeks of driving the green eye never indicated a full charge. I did a trickle for 16 hours and it came right up and has been there ever since. There is a big myth about charging systems. They will maintain approx 70-80% of a battery's capacity but they never FULLY charge it. High output alternators actually reduce battery life because they smack the battery with extremely high current which is not want a battery wants for a long service life. High output alt's came about because of vehicles like police cars that have a lot of add on's(lightbars, high power two way radios, sirens). Collectively these add on's can add up to an excess of 50 amps or more. Conventional 65 or 100 amp units could not maintain an effective enough charge for these vehicles. Believe it or not what is best for a battery is a lower rate of charge for a longer period of time. Ask any dealer mechanic about how many batteries they change in warranty on vehicles with high output units. If the demand in your car is there upgrading is a good idea, but if it's all stock for the most part there is no reason to go over 100 amps with an alt replacement.