This post is for discussion in an associated techtalk thread.

An alternator charging at only 12.6 volts instead of the typical 14.2 volts indicates that it is not functioning properly. Here are some potential issues that could cause this problem:

### 1. **Faulty Voltage Regulator:**
The voltage regulator controls the amount of voltage the alternator produces. If the regulator is malfunctioning, it may not allow the alternator to produce the necessary voltage to properly charge the battery.

### 2. **Worn Brushes or Slip Rings:**
Alternators have brushes that make contact with the slip rings to transfer electrical current. Over time, these brushes can wear down, or the slip rings can become dirty or damaged, leading to reduced electrical output.

### 3. **Bad Alternator Diodes:**
The diodes in the alternator convert AC current to DC current. If one or more diodes are faulty, the alternator may not be able to produce sufficient voltage.

### 4. **Loose or Corroded Connections:**
Loose, corroded, or damaged connections at the alternator, battery, or voltage regulator can cause a drop in the charging voltage. Ensuring all connections are clean and tight is crucial.

### 5. **Drive Belt Issues:**
The alternator is driven by a belt connected to the engine. If this belt is loose, worn, or slipping, it may not spin the alternator fast enough to produce the required voltage.

### 6. **Battery Problems:**
A failing battery can sometimes load the alternator down, preventing it from reaching proper charging voltage. It's essential to check the battery condition as well.

### 7. **Internal Alternator Problems:**
There could be other internal issues within the alternator itself, such as damaged windings or bearings, which would impair its ability to function correctly.

### 8. **Electrical System Load:**
Excessive load on the electrical system, such as numerous accessories running simultaneously, can sometimes cause the alternator to struggle to maintain the correct voltage.

### Troubleshooting Steps:
1. **Check Battery Condition:**
   - Test the battery with a multimeter to ensure it is in good condition and fully charged.

2. **Inspect Connections:**
   - Examine and clean all connections at the battery, alternator, and voltage regulator.

3. **Test the Voltage Regulator:**
   - Check if the voltage regulator is functioning correctly, possibly by swapping it with a known good unit.

4. **Measure Alternator Output:**
   - Use a multimeter to measure the alternator’s output voltage directly at the alternator terminals.

5. **Inspect Drive Belt:**
   - Ensure the drive belt is in good condition and properly tensioned.

6. **Check for Excessive Load:**
   - Turn off all unnecessary electrical accessories and recheck the charging voltage.

7. **Professional Testing:**
   - If initial checks don't reveal the issue, consider having the alternator professionally tested to diagnose internal problems.

By systematically checking these potential causes, you can identify why the alternator is only charging at 12.6 volts and take the appropriate steps to resolve the issue.