. My 1989 Ford Full size Bronco has a new alternator, battery and battery cables. When the engine is running the alternator only brings the voltage of the battery to under 13 volts. Is there any cable that goes director to the battery from the alternator? I checked all the wires and made sure they are connect. Please remember this is free. I believe it is the wiring around the starter solenoid. Maybe I need a wiring diagram showing the wiring under the hood. I can not down load and my printer does not work.
Where is your voltage regulator? Some were on the back of the generator that year and some were the external ones with four terminals. If you have the external one, unplug it and jump terminals "I" and "A" together with a jumper wire in the connector. That's the two on the ends of the plug. Run the engine at idle just long enough to see what the battery voltage comes up to. Don't raise engine speed too much if at all because system voltage can go dangerously high. If the voltage goes to around 15 volts or more, clean the regulator's housing where it bolts to the body, and if that doesn't help, replace it.
If you have the regulator bolted to the back of the generator, check out this page for the test method. You'll be doing the same thing as in the previous test. It's called "full-fielding" the system.