Ok, so the best way to do this is probably to explain everything from the beginning. I bought my truck about 3 1/2 years ago now, and since then It has haunted me with the same problem. It started about a month after I bought the truck, I had replaced the alternator with a new one as the old one (likely factory original) was completely dead after a month of driving. I replaced it with a new unit as well as the voltage regulator, and not just a couple days later it tested bad as well. I had that alternator replaced and the new one seemed to serve me well for the next several months. It should be noted that the battery dummy light only came on when these first 2 alts went bad. After I moved from Florida (where I bought the truck) to Missouri (where I currently live,) I noticed my batteries were going dead as the temprature dropped. the dummy light wasn't coming on, but the voltage on the dash-mounted voltmeter wasn't climbing above 12 volts when at idle with ANY accessory on (ie: headlights, A/C). I didn't realize that the alt was bad, assuming bad batteries because i lacked the knowledge. 1 set of new batteries later, and they were dead in a week. After finally figuring out it was the alternator, i decided to buy my new alternator from somewhere else. I had been buying them from advance auto parts, and decided I would try autozone (caus they have a lifetime warranty on these things) and I was very please with the performance. I replaced both the voltage regulator and alt again, and this time even when idling the voltage never dropped below 14 volts. Until a couple months ago, this was working fine, but then the old problems came back, except this time when i had the alternator bench tested, it tested fine, the handheld tester however said the voltage regulator was bad so away it went. The man at the autozone warranty'd my alternator anyway despite it testing ok (i tested the new unit as well before installation) and the problem still exists. ive thrown 3 more voltage regulators at the problem and it still won't go away. Ive had grounded the voltage regulater casing to the negative battery terminal and testing the alt wiring harness for resistance didn't reveal anything. Please help I need this truck to work and hooking it up to a battery charger every morning is getting frustrating.