When I push the gas pedal, my voltage gauge goes down to 9 and sometimes red battery light comes on. when the engine off if i leave my lights are on inside the truck my battery dies. these are the symptoms. Also, I have 600 wats amp for my speakers. my question is is it my battery or my alternator?? Thank you for your time

 

If you have a multimeter test your alternator for voltage out put. Should be around 14 volts. You test at the main terminal coming off the back of the altermator going to the battery. If you cant get to the terminal you can check at the battery.

Check the voltage of the battery with truck off. It should be around 12 volts. Start the truck and check for voltage should be around 14 volts. If at 14 volts the alternator is charging.

If you dont have a multimeter, with the truck off, loosen the negative battery cable so it can be pulled off by hand but not so loose as it does not make a connection. Start the truck. Then pull the negative cable. If the truck dies your alternator is bad.

I have no experiance with sterio installs. However, when large amps are added it does cause problems if other electronics are not installed to help with the load. I'm not sure if it is a resistor, capacitor, or stater but something along those lines is sometimes required to be installed. Maybe a search for amp or sterio install will have something on it. Hope someone can answer to this. Or I could be totaly incorrect on this one.

 

tomorrow i will try that i dont have a multimeter so i will go with the second one. Thank you

 

Please do not disconnect any battery cables when the truck is running! The voltage spike that occurs can peak at 75 volts! It can cook your computer, your alternator and anything else that doesnt like 75 volts.

A 10 dollar multimeter is a tool that everyone should have in their tool box. Its alot cheaper than replacing parts.

 

you can always go to autozone,advance auto,etc and they will test them both for free.

 

I was in a hurry once so instead of testing my alt myself i stopped at Autozone. My symptoms were similar. Strictly stock truck, when engine rpm increases above 4000 rpm, my battery voltage drops. The teeny bopper that check my truck hooked up to it and went through all the steps. Told me alt was good.

I explained what was going on, ran the engine up to 4500 rpm and voltage dropped battery light came on. Kid tried to explain to me that it was normal: the alt is spinning really really fast and the electrons just cant go through the brushes when it spins that fast so I shouldnt rev the truck that high. After I picked my jaw up off the ground I couldnt help but laugh. I explained to him that I do generators for a living and what he fed me was a whole load of horse stuff. He got angry! Geez!

If you dont know what youre talking about, Just keep your mouth shut.

I still have the same alt on the truck. The only time it drops out is when I pass or have to run down the road to the Fire station.

I believe the ECM is commanding it off for some reason.

I hear there is a fix for this: removing the ecm from the circuit somehow.

Good luck!

 

i dont believe the stereo ampwould have anything to do with it as i am running a 1000w amp with 2 1000w subs and have no fluctuation in my alt gauge, but then again depending on the maker of the amp, the coils could be bigger and harming the alternator, best thing to do if you have an amp that is 600w and up is to buy and hook up a 1 ferad capacitor so you dont have to worry about killing your battery.

when i took my alternator to autozone due to it being loud, they said the bearings were bad and tested it on the monitor and it failed. if you take it to autozone find some 1 that is experienced to run the test

 

I was really busy with work and summer school. I just had a chance to look at it yesterday. I did the test with the multimeter and it was good it showed 14 from the battery and alternator when the engine is one when its off it showed 12. so i took it to autozone and i asked the manager to test it. he tested and passed the test but he said it was 60% charged. the car was just there maybe not more than 5 minutes and i didnt left any light on. he told me maybe i had a corrosion on the battery cables.

 

Buy a new battery (knowing your alternator is good). How old is it? Here in NY between the cold winters and hot summers I'm lucky if I can get 4 years out of a battery. Other thing too is when you run a battery dead they only come back to 90% capacity. Do that enough times - 90% of 90% of 90% etc. and there's not enough left.

 

well I bought the blazer like 1.5 years ago and the guy told me truck had the battery for about couple years it might be the battery but it passed the test. i had this problem when i didnt have my sound system in it too. the battery specifications are cold crank 650 and the other one i believe 700 something.