Hello everyone,

I have a 2003 Silverado 4.8 with a 105a(k68 I believe) alternator and a 3 year old battery. Lately my truck has been very weird where the voltage will jump from about 10 volts all the way to 14.5ish on the gauge while the engine is running at idle or low loads and keep bouncing around between that but when I'm driving it's high (14.5ish) and if I push the brakes at night the lights will flicker(dash lights and headlights) and if I put a high enough load (everything electrical on at once) the voltage will drop nearly to 9 at idle so I believe the alternator is dying and maybe has a bad diode or something funky, AutoZone tested my battery and it said to replace it but couldn't check anything because the charge was 94% but with no loads I measure it at 12.63V which is way within spec and it has no problems running everything and doesn't drain. So should I just replace both or do I have maybe another issue? I should also mention I have an aftermarket sound system with a 500 watt amp and two 12's along with a touchscreen head unit but I've had it for nearly a year with no problems until now. I've heard that a bad diode can cause overcharging and sending alternating current into my system and can damage the battery and the computers and various parts, is this true or should I be good?



ALSO, Ive read that for an 03 Silverado you can simply replace the 105 with a 145amp alternator and all you have to do is change the belt to a 93' belt, the connections are all the same and you don't need to upgrade wires or anything( like doing the "big 3"), I'd rather go that route if it's plug and play.

 

Doing the big 3 is highly recommended anyway, even with a stock truck. It would probably help a little, but it sounds like your alternator is going out, so I would try that first.

 

I am of the opinion as soon as you start modifying the stereo in any significant way its time to upgrade electrical. The big three should be done anytime an amp and subs are added. A 145a alternator is a great upgrade although a 200a is even better. Either will help significantly. Lastly a secondary battery if necessary. Capacitors are stupid don't let anyone convince you to do one.

 

Well I've already ordered the 145, and I plan on doing a big 3 in the near future but will the stock wiring be able to take the 145a going from a 105a?? Also would the 200a your talking about be a plug and play as well or would I absolutely have to upgrade to the big 3 with it?

 

I should also say that I only have the sound system with a 500 watt amp and a touchscreen head unit. Planning on changing the headlights to the led with halos and led taillights(will not be running in H.I.D) and not anything else I can think of except that I can think of other than a phone charger I guess

 

Anyone?

 

big 3?

 

Big 3 is an awesome upgrade no matter the current your flowing.

I would definitely do it its not expenisve and it will inspire you to clean up your engine bay a little too.

Keep in mind that the engine ground is the most important one in the whole system. Your alternator is the originating ground point for everything in the truck and assuming its grounded well to the block the engine to battery ground is the weak link.

-Matt

 

what is the big 3?

 

Its a very common upgrade across all makes and models.

It involves upgrading the wiring to and from your alternator, frame, and battery

Bigger wires and better grounds help take electrical strain off the system and is essential for big current setups such as winches, lots of conventional lighting, and big stereos.


Heres a good general article on it,

How to upgrade the Big Three

If there isn't a thread on how to do it on your vehicle on PT somewhere let me know and I can help you do it but more than likely its on here somewhere.


Its cheap and only a afternoon to do it right I highly recommend doing it.


-Matt