not charging
 

the alternator on my 87 dually went bad, I put a rebuilt one on, thought the problem was fixed. drove around all day, then went to start it, it just clicked like a bad battery, checked the alternator at the local parts store, they said its good. bought a new battery, put it in, the alt, gauge reads just below 13 ( I think it should be just above 13, 13.8) now I noticed the dash lights turn off when the ign. switch is turned off, and the dome light doesn't work anymore.. any Ideas???? thanks.

Re: not charging
 

Good afternoon, Time to check all ground leads that they are clean & connected, both engine and chassis. I also may be a power drain somewhere. Start with the grounds. Almost forgot check the main cables on the battery they may need replacing.

God Bless, Terry

Re: not charging
 

Also check wires at the starter

Re: not charging
 

There is a fusible link between the alternator output and the battery. If this is blown, you get no charge. The battery + cable is connected directly to the starter stud. From that stud radiate several fusible links, one of which connects to the alternator. Check all of your fusible links. A burned one will feel soft, will probably look burned, and will test open circuit on an ohmmeter.

Check if this is the problem without getting under the truck by:
- disconnecting the battery - cable
- measuring ohms from the battery + cable to the alternator output stud.

Infinite ohms means open circuit means burned out fusible link or bad connection.

Actually, any ohms over an ohm or two is trouble. Should read close to zero.

Re: not charging
 

A charged battery is 12.6V but the engine charges at 13.5 or so Volts. After sitting a bit and having a small load the battery voltage should read very close to 12.6. Much under that indicates a lack of charge or bad.
When the key is off, most things should be off. Headlights and horn normally work though.
The dash lights and dome light are controlled by the rheostat in the headlight switch. Crank it right to make things brighter, or all the way to the left to turn on the dome light.
A new battery doesn't mean its good or charged. The old battery may have been good but needed a charge.
Check battery voltage before and after starting. A running engine should be charging the battery so voltage should be above not running voltage, and 13.5V or so if memory serves...