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Voltage Regulator Replacement
 
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Pelican Technical Article:

Voltage Regulator Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$80

Talent:

**

Tools:

13mm, 15mm deep sockets, Philips head screwdriver, floor jack, jack stands, wheel chocks, safety glasses, torque wrench

Applicable Models:

Mercedes-Benz C350 (2008-15)
Mercedes-Benz GLK350 (2010-15)

Parts Required:

Voltage regulator

Hot Tip:

ALWAYS disconnect the battery before beginning

Performance Gain:

Car charges again

Complementary Modification:

Change drive belt

The alternator charges the battery and provides your car with a constant source of electricity while the engine is running. The voltage regulator does just what it says: it regulates the voltage from the alternator. Your battery should read a little more than 12 volts with the engine off. Next check the voltage of your charging system under load, the voltage should be within 13.2: 14.5 volts d/c. To load, have the engine running at idle, turn on the headlights and the HVAC blower motor. Never disconnect a battery cable while the engine is running to test the alternator. You may cause damage to the alternator or other electrical components from the surge in amperage. If your battery appears to be leaking, then your voltage regulator has probably failed. The battery will usually only leak acid if it has been overcharged at a much higher voltage. If the voltage measured at the battery is more than 14.5 volts when the engine is running, then the voltage regulator is probably bad. If your battery has boiled over and has acid overflowing out the top, make sure that you clean up any spilled acid immediately. Dousing the area with a water and baking soda solution should help considerably to neutralize the acid, and prevent it from eating away at the metal.

A fair amount of the time when there is an electrical problem with the charging system it is the voltage regulator. Yet people just swap out the entire alternator because it comes with a new voltage regulator included because it is easier, fixes the problem, and most people do not understand how an electrical system works on their car. If your electrical issues are caused by a faulty voltage regulator you can save yourself a lot of money by just replacing the defective part.

You will have to take the alternator out of the car to replace the voltage regulator.
Figure 1

You will have to take the alternator out of the car to replace the voltage regulator. Please see our article on replacing your alternator.

Turn your alternator pulley side down on your bench.
Figure 2

Turn your alternator pulley side down on your bench. The voltage regulator is partially obscured by a plastic cover on the back of the alternator. Remove the two bolts, one 13mm (yellow arrow) and one 15mm (red arrow) along with the Philips head screw (green arrow).

Lift the cover off the back of the alternator.
Figure 3

Lift the cover off the back of the alternator.

With the cover off you will see the three Philips head screws (red arrows) that hold the regulator in place.
Figure 4

With the cover off you will see the three Philips head screws (red arrows) that hold the regulator in place. Remove the three screws and lift the voltage regulator from the alternator.

You can now see the two brushes (red arrows) that make contact with the poles on the alternator.
Figure 5

You can now see the two "brushes" (red arrows) that make contact with the poles on the alternator. Check the condition of the brushes for excessive wear or pitting.

The brushes are held in place against the polls by springs that can wear out; push them down with your finger and they should pop right back up.
Figure 6

The brushes are held in place against the polls by springs that can wear out; push them down with your finger and they should pop right back up.

While the regulator is out make sure you check the condition of the poles (red arrows) on the alternator: they can be discolored but should not be excessively worn, corroded and should not have grooves worn in them.
Figure 7

While the regulator is out make sure you check the condition of the poles (red arrows) on the alternator: they can be discolored but should not be excessively worn, corroded and should not have grooves worn in them. Installation is the reverse of removal.


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