Can the computer on a 1991 dakota 3.9 be bypassed so alternator will charge?

No, you can't completely bypass the computer on a 1991 Dodge Dakota 3.9L to charge the battery. While the system isn't as sophisticated as later models, the computer still plays a role in the charging system. The alternator is controlled by the PCM (Powertrain Control Module) through a field current wire. Simply connecting the alternator's output directly to the battery will likely damage the alternator or the charging system and could result in erratic behavior.

While you might be able to jury-rig a connection to charge the battery in an emergency, it won't be a proper or safe long-term solution. The problem needs to be diagnosed and fixed. The issue could be:

* Alternator: The alternator itself could be faulty.

* Wiring: There might be a break or short in the wiring between the alternator, the PCM, and the battery.

* PCM: While less likely, the PCM could be faulty.

* Fuses/Relays: A blown fuse or bad relay could interrupt the charging circuit.

Instead of bypassing the system, you should:

1. Check the alternator: Have it tested at an auto parts store to see if it's putting out the correct voltage.

2. Check the fuses and relays: Locate the fuses and relays related to the charging system in your owner's manual or online and check for damage.

3. Inspect the wiring: Look for any damaged, corroded, or loose wiring connections between the alternator, battery, and PCM.

4. Professional diagnosis: If you can't find the problem yourself, take it to a mechanic or auto electrician for proper diagnosis and repair.

Attempting to bypass the computer without understanding the electrical system is dangerous and could lead to further damage. It's far safer and more reliable to find and fix the underlying cause of the charging problem.