911SC Technical Article - Voltage Regulator Replacement

[mca]

1982 911 SC Voltage Regulator Replacement

First Time Around Difficulty Rating: 4 out of 10
Second Time Around Difficulty Rating: 3 out of 10
Patience Rating: 6 out of 10

I wrote this for DIYers that are new to the game. I welcome comments, corrections, and additions. I performed this task with the help of Wayne Dempsey’s 101 Projects for Your Porsche 911.

First things first … the voltage regulator is located on the back side (side facing front of car) of the alternator. The alternator sits inside of the fan housing. The fan housing is the big fan that you see in engine bay.

I suggest that this job is performed with stubby wrenches (ratchet style) and the correct fan belt tool. Thanks to toddu for suggesting the stubby wrenches. They proved to be a huge time and frustration saver. Thanks to timc for helping me sort out a battery issue that I encountered during the job.

Step 1: A/C Compressor Belt
Disconnect battery first!
If you have a working A/C system, then you must first remove the A/C compressor belt. I have the rotary style compressor so I can not speak to the process of removing the belt for other compressors.
Three screws must be removed. One screw -the tensioning screw on the left side of the compressor that points to the fan housing – need only be loosened to the point where it is almost removed. I believe that all of these require 13mm wrench. See photos.
The compressor may then be tilted toward the fan housing and a little bit towards the rear of the car. This will allow the tension on the belt to slacken sufficiently for removal from the compressor and then from the pulley by the fan housing.





Step 2: Fan Belt Removal
Use the proper pulley wrench to hold the pulley steady and a 24mm socket to remove the retaining nut that holds the entire assembly together. Fan belt removal is covered thoroughly on this forum and elsewhere so I won’t go into any further detail.
As a side note, my old fan belt had 4 shims on the inside (towards front end of car) and 2 shims on the outside (towards rear of car). After installing my new fan belt, I had 2 shims on the inside and 4 shims on the outside.

Step 3: Remove Fan Housing
Remove coil by removing the 2 bolts that secure the coil onto the fan housing and tuck to side. Don’t remove or disconnect any of the coil’s wiring.
Loosen and disconnect the long metal strap that runs across the top of the fan housing. I tied the straps back with strings to keep them from interfering with my work.





Step 4: Pull Fan Housing from Engine
Now, carefully pull the fan housing toward you (toward rear of car) just enough so that you can see the plastic air flow guide that surrounds the alternator and the wires that are attached to the alternator. You want to be careful here because the wires are the only thing holding the fan housing in place.
The plastic air flow guide has 5 nuts that must be removed in order to gain access to the wiring connections at the back of the alternator. This was a little time consuming for me because I had a hard time getting my hands in there and I didn’t want to drop any of the nuts while trying to remove them. I rotated the fan housing freely in order to gain access to all 5 nuts.
After you remove the nuts, you can push the plastic air flow guide away from you (towards front of car) and you will see the wire connections to the alternator. These wires may be delicate from years and years of exposure to engine heat – so treat them accordingly. I wasn’t too terribly careful with moving them - but I was careful not to bend them.
Take pictures or mark the wires before disconnecting them from the alternator so that you will be able to re-connect them properly.
Disconnect the wires and pull fan housing away from car. You will now have access to the voltage regulator which is on the back side of the alternator where you just finished disconnecting wires. Go ahead and pull the fan off too. It is not secured by anything and you won’t want it to drop to the ground because it could easily break.





Step 5: Remove Alternator from Fan Housing
Going into this project, I was under the impression that I would not have to remove the alternator from the fan housing in order to replace the voltage regulator. Unfortunately I saw no alternative as the voltage regulator was being hindered by the lip of the fan housing. This may or may not be the same for you! I suggest that you try to remove the regulator first, then proceed to separate the alternator from the fan housing if needed.
If you see any nuts on the 6 studs, remove them now. I had one nut that was on the stud closest to the voltage regulator. Not sure if this is common, but I can only speak from what I experienced.
The alternator should pull away from the fan house - try shaking the housing if need to help free the alternator.
My alternator was quite snug so I used the method of gently tapping the 6 studs (marked in red in photo) with a soft mallet. I sat on a bucket and squeezed the entire fan housing between my thighs – voltage regulator facing towards the sky. I kept my left hand between the fan housing and the floor to catch the alternator once it was freed from the housing. I then used my right hand to tap on the 6 studs with a soft mallet - moving from one stud to the stud opposite of the one I was working on. After a few minutes, the alternator easily worked its way out and into my left hand. Be careful and take your time because you don’t want to damage the alternator or the stud threads.
Now that you have freed the alternator from the fan housing, you should be able to replace the voltage regulator. This is super easy as it is secured by 2 screws and 2 wires that are clipped on to the alternator – remove screws and pull wires away from alternator. You may have to back out the one stud that is closest to the voltage regulator in order to gain enough clearance to pull the regulator away from the alternator.
Now is a good time to take a break and clean the fan / fan housing before reassembly. I used a little bit of gasoline, rubber gloves and a rag to clean the gunk off. Not sure if gasoline is the best or wisest thing to use, but it worked well and it was all that I had.





Step 6: Reinstall Process
Simply reverse the first 5 steps!
After reinstalling or replacing your fan belt and tightening the pulley nut, you will need to turn the engine over to ‘un-pinch’ the fan belt. Do this by putting your car in neutral, use the same 24mm socket on the pulley nut and turn clockwise. You will likely have to use your other hand to place tension on the belt so that it will turn the engine – just press on the belt midway between the pulleys and then turn the nut. You will see the belt ride up into its proper location. I won’t go into further detail here because this process is well documented.

NOTES:
It turned out that my failed voltage regulator destroyed my 2 month old battery. I completed the job of replacing my voltage regulator and then tried to start my car – no dice! I felt sick to my stomach thinking that I had screwed up royally. Using a multimeter I measured 9.5 Volts at the batter which was clearly not enough to get her started. After replacing the battery (red top Optima at $180 – ouch), the 911SC fired right up!

[mca]

Oops! Forgot picture showing the tie back of the metal bands.

[304065]

The first thing you should do is disconnect the battery. If somebody tries to disconnect the alternator while the battery is connected, and the wrench they are using to loosen the nut on the B+ terminal touches ground anywhere, they will have an 800 amp short circuit, which can easily kill you.

[Lorenfb]

"Remove alternator from fan housing by gently tapping the 6 studs (marked in red in photot) with a soft mallet. "

Total Mickey Mouse!!!!!!!

This usually results in damaged threads. Good Porsche mechanics NEVER pound
on ANY threaded bolts/studs. They use a block of wood to gently tap the housing
on to "shake" the alternator out.

[on-ramp]

Originally posted by Lorenfb
"Remove alternator from fan housing by gently tapping the 6 studs (marked in red in photot) with a soft mallet. "

Total Mickey Mouse!!!!!!!

This usually results in damaged threads. Good Porsche mechanics NEVER pound
on ANY threaded bolts/studs. They use a block of wood to gently tap the housing
on to "shake" the alternator out.

EXACTLY! "Gently tapping" on anything is always useless on a 20+ year old Porsche 911.

[mca]

Thanks for the comments thus far.

john_cramer
YES! Disconnect the battery first! I forgot to mention that.

Lorenfb
You said "Good Porsche mechanics NEVER pound
on ANY threaded bolts/studs."
If I recall correctly, the 101 Projects book says to gently and evenly tap on the studs if the alternator does not pully away from the fan housing - but to be very very careful not to damage the threads. I will confirm this evening when I have the book in hand.

on-ramp
I hardly think tapping is "always useless" on a 20+ year old car. Just b/c my car is 20+ years doesn't mean all of the parts are that old. I understand, in the scenario regarding the alternator, that the threads could be at risk. You point is considered and well taken. But to say that tapping with a soft mallet is "always useless" ... seems a little far fetched.

Keep the comments coming! Revealing my mistakes will help me learn and will help others down the road.

[Lorenfb]

"If I recall correctly, the 101 Projects book says"

So!!!!!!!!!!

[mca]

Yikes.

[vash]

it is way better than any tech article i have written. mine are blank.

[holtjv]

thanks for this, mca, doing the replacement in my sc this weekend. Jack

[mca]

Sure thing Jack! Best wishes on the project.

[Wavey]

Originally posted by Lorenfb
So!!!!!!!!!!

Wow - TEN exclamation points. Now that's emphatic!

Loren, is it at all possible for you to respond in a way that is NOT ill-mannered and rude?

I swear to God, we're going to make a gentleman out of you yet.

[rburn]

Nice write up and pictures. yes it's always nice to add
"disconnect battery" but i think that's implied in any type of work involving the electrical system.

A block of Wood... hahaha now that is funny.

[Lorenfb]

"1982 911 SC Voltage Regulator Replacement"

Rarely a proper long term alternator fix if the alternator has > 60K miles;

a. the slip rings need replacement
b. the bearings need replacement

The only time that a regulator should be replaced is if the alternator
was recently replaced (< 25K) and a marginal charging condition exists.

"I hardly think tapping is "always useless" on a 20+ year old car."

Maybe for a job at Pep Boys or Auto Zone.

[Keith Perry]

MCA, thank you. This afternoon I started replacing my fan ring, having pulled everything apart a few weeks ago. My hand drawn take apart drawing seemed clear at first, but I rotated the alternator and got lost. Your picture got me done. Thanks.

[SCWDP911]

sub'd

[beepbeep]

Originally Posted by john_cramer

The first thing you should do is disconnect the battery. If somebody tries to disconnect the alternator while the battery is connected, and the wrench they are using to loosen the nut on the B+ terminal touches ground anywhere, they will have an 800 amp short circuit, which can easily kill you.

Great article. I just want to say that 12V system is unlikely to kill you in any way. You might burn yourself by heated cables, but body resistance is much too high to allow any meningsful current to flow trough it by touching 12V.

[David E. Clark]

Originally Posted by beepbeep

Great article. I just want to say that 12V system is unlikely to kill you in any way. You might burn yourself by heated cables, but body resistance is much too high to allow any meningsful current to flow trough it by touching 12V.

The typical human body has a resistance of about 5,000 ohms and if the skin is wet the resistance is much lower, down to about 1,000 ohms. Assuming a typical car battery puts out about 500 amps, a person could safely put their thumbs on the terminals without serious injury. This is because 12 volts divided their body's resistance simply does not produce enough amps to cause death. Thus even if you were soaking wet and touched both terminals of a 12 volt car battery, the current passing through your body would be 12 volts ÷ 1,000 ohms = 0.012 amps. This is nowhere near enough to kill you!

That said, John is right to say always disconnect the battery first. The risk of short circuits with all those expensive electronics is much more than I am willing to take. Great article and nice pictures!

[RoninLB]

disconnect battery especially if you wear silver jewelry or working around gas.

oak is better than pine for thread use.

imo if your fingernail can grab a groove on the slip rings it's toast. If you replace with very bad slip rings voltage may be erratic.

the regulator connector to the rings can be shaped giving a better shot at operaton.






And guess where this bastard came from when 3,000+ miles from home?

[304065]

Originally Posted by David E. Clark

The typical human body has a resistance of about 5,000 ohms and if the skin is wet the resistance is much lower, down to about 1,000 ohms. Assuming a typical car battery puts out about 500 amps, a person could safely put their thumbs on the terminals without serious injury. This is because 12 volts divided their body's resistance simply does not produce enough amps to cause death. Thus even if you were soaking wet and touched both terminals of a 12 volt car battery, the current passing through your body would be 12 volts ÷ 1,000 ohms = 0.012 amps. This is nowhere near enough to kill you!

That said, John is right to say always disconnect the battery first. The risk of short circuits with all those expensive electronics is much more than I am willing to take. Great article and nice pictures!

Having accidentally contacted the battery positive terminal on my race car's electrical cutoff switch with a stainless steel watch, it's something I never want to do again. Here's some more information below.

The human body is approximately 70% water and makes an excellent conductor. Human-body resistance varies depending on how well you are grounded, your age, your size, and your gender. The amount of perspiration on your body also affects your resistance; more perspiration increases your vulnerability. To illustrate how a 120V wall-outlet voltage can affect a person, you divide the 120V voltage by the resistance to yield the current. For a high body resistance, dividing 120V by 100 k yields 1.2-mA current. For medium and low body resistance, divide the 120V by 10k and 1 k, respectively, yielding 12 and 120 mA, respectively. At 1.2 mA, a human body would be on the threshold of feeling a tingling sensation; at 12 mA, the human body would feel the beginning of a freezing, or "can't-let-go," feeling. At 120 mA, the feeling would be extreme pain and possible ventricular fibrillation.

Current follows the path of least resistance to ground. Arteries, nerves, and muscles have low resistance, whereas bone, fat, and tendons have relatively high resistance. The human brain, heart, and nervous system are the most sensitive. These body parts feel a shock with a current as low as 0.5 mA. For hand-to-foot currents higher than 5 mA, a victim can't free himself from the source. Even if the jolt throws a victim free of the power source, he can go into respiratory arrest, cardiac arrest, or both. Currents greater than 20 mA may deliver a lethal shock. Jolts higher than 1A throw the heart into a contraction; internal body heating is significant. Thermal burns may result in death or the loss of a limb long after the incident.

The factors that determine the severity of an electrical hazard and its effect on the human body are voltage, current, resistance, frequency, duration, and pathway. Voltage forces current to flow, which can damage the heart or brain or cause involuntary muscle contractions. Current determines the extent of the damage and can cause heating of external and internal human-body tissues and organs. Human-body resistance varies depending on how dry or moist the body is and on the current's path through the body. Current passing though the arm generates more thermal damage than through the abdomen because the arm has a smaller cross-sectional area than the abdomen. Frequency also influences the danger; ac causes more ventricular fibrillation than dc, but both can lead to injuries. Duration affects the severity of heating human tissues and organs; the longer the contact, the greater the damage. A 60% chance of mortality exists for a hand-to-hand current pathway through the heart, and 20% mortality exists for a hand-to-foot path. An old adage says to place one hand in your pocket when working near hazardous electricity so that current does not pass through your chest. A better recommendation is not to touch hazardous voltages!

http://fringe.davesource.com/Fringe/Information/Hazardous_Voltage_Primer/