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Voltage Regulator Replacement
 

Pelican Technical Article:

Voltage Regulator Replacement

Steve Vernon

Time:

30 minutes30 mins

Tab:

$35 to $50

Talent:

**

Tools:

Philips head screwdriver

Applicable Models:

BMW E10 2002 Coupe/Conv (1967-76)
BMW E21 320i Coupe (1977-83)

Parts Required:

New Voltage Regulator

Hot Tip:

ALWAYS disconnect the battery before beginning

Performance Gain:

Car charges again

Complementary Modification:

Replace the 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 significant amount of the time when there is an electrical problem with the charging system it is the voltage regulator. People typically just swap out the entire alternator because it comes with a new voltage regulator included and 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 out car to replace the voltage regulator. Please see our article on replacing your alternator. You must perform this work first.

The voltage regulator is mounted to the alternator (red arrow) so you must remove the alternator from the engine to replace the regulator.
Figure 1

The voltage regulator is mounted to the alternator (red arrow) so you must remove the alternator from the engine to replace the regulator. Please see our article on alternator replacement.

With the alternator on your bench you will want to remove the two Philips heads screws holding the regulator in place (red arrows).
Figure 2

With the alternator on your bench you will want to remove the two Philips heads screws holding the regulator in place (red arrows). Use care with these screws as they can get corroded in place. This was not the case in our project car as we had the pleasure of working on the Clarion Build's BMW 2002. Everything was fully restored to factory new condition.

Pull the regulator (red arrow) out from the alternator.
Figure 3

Pull the regulator (red arrow) out from the alternator. There is a metal strip that works as a ground for the regulator (yellow arrow). Do not damage this while removing the regulator.

You can now see the two brushes that make contact with the poles on the alternator.
Figure 4

You can now see the two "brushes" that make contact with the poles on the alternator. These are held in place against the poles by springs that can wear out; the brushes can also wear out or become excessively corroded over time.

Push the brushes down.
Figure 5

Push the brushes down. They should both pop right back up.

While the regulator is out make sure you check the condition of the poles on the alternator.
Figure 6

While the regulator is out make sure you check the condition of the poles on the alternator. They can be discolored but should not be excessively worn, corroded and should not have grooves worn in them. A replacement regulator will not make proper contact with the poles. Installation is the reverse of removal. Make sure the ground on the regulator makes contact with the ground on the alternator (yellow arrow).



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Page last updated: Wed 12/13/2017 03:01:56 AM