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Voltage Regulator and Impeller Replacement
 
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Pelican Technical Article:

Voltage Regulator and Impeller Replacement

Steve Vernon

Time:

30 minutes30 mins

Tab:

$80 to $280

Talent:

**

Tools:

Philips head screwdriver, 16mm socket, M10 12 point

Applicable Models:

Porsche 993 Carrera (1995-98)
Porsche 993 Carrera 4 (1995-98)
Porsche 993 Carrera 4S (1996-98)
Porsche 993 Carrera S (1998)
Porsche 993 Targa (1996-98)
Porsche 993 Turbo (1996-97)

Parts Required:

Voltage Regulator

Hot Tip:

ALWAYS disconnect the battery before beginning

Performance Gain:

Car charges again

Complementary Modification:

Replace the belts

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 the system, have the engine running at idle, turn on headlights and HVAC blower motor.

Never disconnect a battery cable while engine is running to test alternator, you may cause damage to 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 large 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 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 your self a lot of money by just replacing the defective part.

There is an impeller on the rear of the alternator, if this is damaged in any way you want to replace this.

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 alternator, like on all air-cooled 911 motors is behind the cooling fan (red arrow).
Figure 1

The alternator, like on all air-cooled 911 motors is behind the cooling fan (red arrow). 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.

With the fan, alternator and housing removed you can either separate the alternator and fan (yellow arrow) from the housing (red arrow) or work with them together.
Figure 2

With the fan, alternator and housing removed you can either separate the alternator and fan (yellow arrow) from the housing (red arrow) or work with them together.

The nice thing about replacing the voltage regulator is you do not need to separate the alternator from the fan, so yeah.
Figure 3

The nice thing about replacing the voltage regulator is you do not need to separate the alternator from the fan, so yeah. We separated them because we had to replace the fan shaft bearing. On the rear of the alternator you will see the voltage regulator (yellow arrow) and the impeller (red arrow). If you are not replacing the impeller you do NOT need to remove it. We removed it because the Philips head screws were on really tight and we could not get enough purchase on them without removing the impeller.

With the alternator on your bench you will want to remove the two Philips heads screws holding the regulator in place (red arrows).
Figure 4

With the alternator on your bench you will want to remove the two Philips heads screws holding the regulator in place (red arrows). Be prepared to use an impact screwdriver here as you do not want to strip out these screws and they can get corroded in place.

Pull the regulator (red arrow) out from the alternator and you can see the two brushes that make contact with the poles on the alternator.
Figure 5

Pull the regulator (red arrow) out from the alternator and you can see the two "brushes" that make contact with the poles on the alternator. These are held in place against the polls by springs that can wear out; the brushes can also wear out or become excessively corroded over time.

While the regulator is out make sure you check the condition of the poles on the alternator (red arrows): they can be discolored but should not be excessively worn, corroded and should not have grooves worn in them or a replacement regulator will not make proper contact with the poles.
Figure 6

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

To remove the impeller for better access to the screws holding the regulator in or to replace it you will need to counter hold the alternator shaft with a M10 12 point socket (red arrow) and use a 16mm socket to break the nut loose; there can be thread locker on the impeller shaft so you may need a friend to help hold the alternator shaft while you break the nut loose (yellow arrow).
Figure 7

To remove the impeller for better access to the screws holding the regulator in or to replace it you will need to counter hold the alternator shaft with a M10 12 point socket (red arrow) and use a 16mm socket to break the nut loose; there can be thread locker on the impeller shaft so you may need a friend to help hold the alternator shaft while you break the nut loose (yellow arrow). Then you can turn the impeller until it slides off the shaft.

Installation of the impeller is the reverse of removal.
Figure 8

Installation of the impeller is the reverse of removal.

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