How to Install a 12V Voltage Regulator

Written by mike frees
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How to Install a 12V Voltage Regulator
(Jupiterimages/liquidlibrary/Getty Images)

The voltage regulator is an important part of your car's electrical system, ensuring that the proper voltage is fed to the battery. If the voltage regulator fails, it could result in a dead or damaged battery. Most modern cars are equipped with alternators or power train control modules (PCMs) that incorporate the voltage regulator as an integral part; if the regulator fails, the alternator or PCM will have to be replaced. Older cars and some current models have separate voltage regulators that can be replaced individually if necessary.

Skill level:

Things you need

  • New voltage regulator
  • Wrench
  • Screwdriver
  • Electrical tape
  • Pliers
  • Fine sandpaper
  • Electrical contact cleaner
  • Fine (600-grit) sandpaper
  • Volt/ohm meter

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  1. 1

    Remove the ground cable from the battery. Carefully examine the old regulator before removing it. It will be bolted to the alternator and will have several wires attached to it. Note the position and colour of each wire; you should mark the new regulator or label the wires to indicate which wire should be attached to which terminal.

  2. 2

    Detach the wires from the old regulator. Tape the end of the battery wire to avoid grounding it against a metal part and causing sparks. Remove the old voltage regulator. Some are attached with two screws, others have two or four bolts. Carefully lift the regulator away from the alternator. There will be two carbon blocks, called "brushes," on the bottom of the regulator. If the brushes are in good condition and the new voltage regulator is not equipped with them, you may reuse the old brushes. Carefully clean the contact ends of the brushes with fine sandpaper and spray with electrical contact cleaner. Notice that the contact ends of the brushes will show a concave wear pattern from the armature of the alternator. Insert them into the new voltage regulator so that the wear pattern will align correctly.

  3. 3

    Install the new voltage regulator onto the alternator, taking care not to damage the brushes as you insert them into place. Bolt the regulator in place, then reattach the wires according to your tags or labels. Be sure all wires are securely attached. Reconnect the ground cable to the battery. Start the car and measure the voltage being applied to the battery when running at 1000-1200 RPM. A normal reading should be in the 13.5 to 14.5 volt range. Some voltage regulators are equipped with a voltage adjustment strap. If yours is so equipped and the voltage range is out of limits for your car, follow the adjustment instructions supplied with the voltage regulator to correct it.

Tips and warnings

  • On some cars it may be necessary to remove the alternator in order to access the voltage regulator.
  • If working underneath your car, be sure the car is securely supported by jack stands or a lift; do not trust a car jack.

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