How to Rebuild a Faulty Generator
95 percent of the time, a malfunctioning automotive generator can be traced back to worn brushes. And while replacing the entire generator unit should definitely fix the problem, you can save the generator and in replacement costs by rebuilding it and replacing only the generator brushes. Rebuilding the generator is also fairly easy, and you can do the entire process at home provided that you have the tools on hand.
Difficulty level: Moderate
What you'll need:
- Generator repair kit
- Ratchet and socket set
- Electric drill
- Stiff brush
Step 1: Open the hood and disconnect the battery leads. Make sure that the ignition is switched off to avoid electric shock.
Step 2: Detach the air filter for easier access to the generator. If you have a cold air intake or a similar performance air intake system, you may also need to unbolt the filter housing or air box and the air intake pipe.
Step 3: Locate and remove the electrical wires leading to and from the generator. Mark the location of the wires with a grease pen before removing them.
Step 4: Remove the serpentine belt connecting the generator to the engine. Wedge a long-handled ratchet or a serpentine belt tool into the drive into the square opening of the tensioner arm and rotate it as far as it will turn. Doing so will release the tension and allow you to remove the belt from the pulley.
Step 5: Remove the generator's mounting bolts and pull the generator out. Take note where the bolts are mounted on the arm.
Step 6: Unscrew the bolts holding the plastic cover into the back of the generator and pull the cover out.
Step 7: Inspect the bearing. If the bearings appear loose or make noise when it spins, it has to be replaced.
Step 8: Loosen and remove the screw holding the resistors in place. Doing so will expose the rectifier assembly.
Step 9: Pry out the soldered leads and unscrew the rectifier mounting bolts. Pull the rectifier out.
Step 10: Install the new rectifier. Replace the mounting screws and solder back the lead wires.
Step 11: Unscrew the brush assembly cover and remove the brush assembly. Make sure that the springs and the brushes do not pop out as you do this.
Step 12: Remove the brushes. In some models, this can be as simple as pulling out the brush from a channel. If the brush is soldered in place, use a small drill bit to remove the solder from the brush. Make sure that all the springs are accounted for; these are not usually included with the new brushes.
Step 13: Using a stiff brush, clean the area around the armature shaft where the brushes come in contact with.
Step 14: Install the replacement brushes. Depress the spring and push the brush wire into the slot, then put the spring holding the brush in the hole.
Step 15: Detach the voltage regulator. Use an ohmmeter to determine if the diodes are receiving the proper current. If not, replace the regulator.
Step 16: Replace the cover and the resistors and put the generator back to its original position.
Step 17: Reconnect the electrical wires and the serpentine belt. Make sure that the belt is at the right tension.
Step 18: Reinstall the air filter and other air intake parts you have removed. Reconnect the battery leads.