[graphic66]

Speaking of the tach, do not turn the stud that the tach wire hooks to on the alternator even a tiny bit or you will break off the wire inside the alternator and your tach wont work until you open up the alternator and solder the wire back on. These alternators are as basic as they can be. A few diodes and a couple of bearings and some brushes, that's it. Good idea to grease the bearings when you split one open.

 

[graphic66]

OK, first does your red alternator light come on when the key is on and the truck is not running. If not, that is your problem. It must work or you will not be charging period. The trickle of current through the bulb excites the windings. To get the tach wire off, clean the threads on the end of the stud real good and spray lube it. You may need to hold the end of the stud with pliers very carefully and when it comes loose clean up the threads you dicked up with a file, die or another nut the same size before taking the nut completely off. It may be easier to cut the wire flush at the alternator and do it on the bench, real easy if the alternator is split open. But check that bulb first, no bulb= no charge

 

[graphic66]

Yes, you should get 14-14.5V running and 11.5-12.5V not running. The difference should be noticable. You can also check with just the headlights, they should get brighter when you start it up. And if it's not charging your Alt. light should come on when running and when not running. Make sure that light works before you go any further. You could also just have the problem that has probably sold more batteries and alternators than just about anything, bad battery connections. They can look good but they can be corroded or loose. If you can move the battery post connectors by hand you most definitely have a problem there.