i recently noticed some strange noises coming through the stereo and when i test my voltage while the truck is running my voltage is going up and down and spiking constantly. from 13.8 to as high as 15.9, i was told this could be a bad alternator or the voltage regulator in the alternator. where or how can i test this and are those regulators able to be replaced or would i have to get a new alt?

 

Hate to break it to you but there is not voltage regulator like in the old days. The PCM regulates the alt now.

But when you are using a meter and testing voltage, are you testing on one circuit like the power wire to the radio or other places like at the ODBII port and battery post and cig light? You could have an issue with a circuit and not necessarily the entire truck.

 

ah gotcha, yeah tested from multiple places all show the same thing

 

A few things to test

Bad Battery / or cables
Load test Battery / Check battery cables and Alt cable. Also check Alt Ground (pin 2 on the two wire connector)

Bad Batt temp sensor
Well you'll need a scan tool to see what its showing to the PCM.

Bad Alternator Diodes (this will cause noise on radio)
Put your meter to AC voltage and see if you have more than 0.5 AC volts leaking

Intermittent short to ground on the Alt field control could be wire or internal on Alt.

Bad PCM
If everything else is good this has the voltage regulator built into it.

 

ok ill check those out at lunch and see whats up thx

 

ok checked truck with my scan tool no codes present

 

I'd say you've got high resistance somewhere's like a short to ground, you could have dirty terminals or a loose terminal. These will cause intermittent issue's like you described. I would check all of your connections and probe your lines for any voltage drop or excessive resistance.
There's a nut on the backside of the alt, make sure those lines are secured tight by the nut(there's a rubber boot over the lines). Check the nut on the battery terminals split under the hood. Check your ground strap on your frame.

 

ok update to this, me and my buddy just put anew ground cable on, no change there, got the alt checked at advanced auto parts ill post the stats in pdf link http://www.mediafire.com/?3uzhmmslbme342e that was fine, when they did the test it never got above 14.7 so thinking it might be the voltage regulator in the pcm, but if its not pulling a code theres no real way to test that?? i still have those other things to test so will let you all know.
thx

 

The only way to test the PCM is to know someone with a StarScan tool or take it to the dealer.

 

eeek those things are expensive, they dont make any good alternative to those do they?