I just completed the removal / replacement of the voltage regulator on my 85 Carrera. I'm posting this to the list as an aid to those who may go through this repair, or need to simply remove the alternator or fan assembly alone. The regulator is mounted to the backside of the alternator on the 84-89 models, and this procedure applies to those cars.
1.) Power down the system by removing the negative ( ground) cable from the battery. If you suspect an overcharging condition from the failed regulator (likely), now might also be the time to remove the battery entirely and inspect that area for acid damage due to a boiling battery. Paint / fix as necessary.
2.) At the engine, remove the A/C belt. Loosen the 4 vertical bolts that hold the A/C to its mounting plate, and also back-off the jack screw (horizontally - on the right). Slide compressor to the left, ease belt off of pulley. Note: these are not metric bolts. These are 1/2" head, not 13 mm. Most Porsche A/C hardware is not metric.
3.) Loosen fan belt . Keep track of the shims ( I had 6 shims total), and note the number of shims under the pulley, and how many were on the outside. Use all the shims when you put the belt back on later. You will damage the alternator shaft if you don't use the proper number of "outside" shims to get to the 6 total.
4.) Locate the ignition wires running on top of the fan shroud. There are two, 10mm ( head) bolts that secure the wires into the fan shroud, at about the "11 o'clock" and " 1 o'clock" positions . Remove these bolts.
5.) Remove a similar bolt at the "9 o'clock" position on the fan shroud, near the distributor. This is a shorter version of the other two. Don't mix them up.
6.) Remove the allen bolt ( 6mm allen wrench) securing the large fan strap that holds the fan housing in place. Push the ignition wires back, and "lift" ( bend ) the strap up, to gain access for the next steps.
7.) Pull alternator "out" toward you. It will move only a small amount, until the fan housing contacts the back side of the crank-mounted fan pulley. Wiggle / tilt the unit until it comes out further- restrained only now by the attached wires. The housing will "just" clear the fiberglass shroud. You now face a small "wedge" opening at the top (between the housing and the shroud) that you will need to do your work. Patience and small hands are a plus.
8.) A funnel-shaped"air duct" with vanes, is attached to the back of the alternator. It is attached by three , 8mm ( head) nuts on the backside of the alternator. These 3 nuts are in a "staggered" arrangement with 3 other nuts on the alternator backside (6 total). We won't worry about the other 3 for now- can't access them anyway. We're only interested in the 3 that remove the air duct. Do this carefully, there isn't much space, and there's a good chance of losing the nuts/washers. Take your time , and take breaks, if necessary. Separate the air duct from alternator ( push air duct back).
9.) The regulator , and mounting wires should now be in view. Remove wires, noting their positions. From your viewing vantage point (from fan end of alternator), with the regulator on "top", the red wire was at the bottom, blue to left, brown ( 2 wires) to right. Note that the red wire uses a 10mm head bolt, brown uses 8mm, and blue uses 7mm. I guess this is supposed to help us, if we don't remember the wire locations (!).
10.) Now the entire cast fan housing , with attached alternator, can be removed from car. If you're only going to replace the regulator, your'e there. The regulator is held on by two, 8mm bolt heads. Note yellow and blue spade connectors and their locations, and replace. If you want the alternator removed for refurbishment (advised), continue to next step.
11.)You will now note the "other" three, 8mm head nuts ( that you couldn't get to earlier when removing the air-duct). These 3 hold the alternator to the cast fan housing . Remove these 3 nuts, noting their location [ that is, whether or not they were included in holding the air-duct funnel. I used this approach: the nut that straddled the regulator centerline DID NOT hold the air-duct funnel. Every "other" nut ( in a staggered, 120 degree pattern) also DID NOT hold the duct. The remaining three DID hold the air duct. Alternator will likely be "frozen" to the housing. With caution, use a hardwood ( or such) to tap on the 6 bolts to get it out. I even used heat from a hair drier to "expand" the housing, which helped. Patience ! Go in a circular pattern. I used a metal hammer, which worked, but I "flattened" the end of the bolts slightly causing grief when re-installing the nuts.Don't do this !
12.) Next is fan removal. Likewise, it will appear frozen to the shaft. Support the backside of the fan in the corner of a wooden box ("blocking the fan"), and allow clearance for the alternator to fall out ( not too far!) Allow maybe 2 inches of drop HEIGHT and place cushioning material underneath). Tap fan shaft end with hardwood block , and unit should drop out. Don't loose the shaft key. Alternator is now out for repair, which a local shop did for me for $75 ( new bearing , slip rings, and bench testing).
Re-installation is the reverse of the procedure.
1.) I used anti-seize on the fan shaft , and the mating surface of the cast fan housing "bore" that accepts the alternator. This should help keep the units from "freezing" together again.
2.) I bought new 8mm head ( 5 mm thread) nylock nuts for the 6 nuts on the backside of the alternator. Just added insurance.
3.) When re-attaching the wires, don't just note the proper mounting locations. Also try to locate the wires radially inward as much as possible. This helps later air-duct- attachment.
3.) When re-attaching the air duct, you can "rotate" the fan / housing / alternator ,so your "work" ( in re-attaching nuts) will always be "on top". I believe there was a lot of rotational "give" in a CCW rotation , and not that much CW. Experiment. Rotate back to original position to continue the installation.
4.) Re-installing the cast housing into the fiberglass shroud will again be difficult. Lifting and tilting before re-entry is advisable.
5.) Push housing back as far as it will go. There is a "peg" on the engine part of the fan support , that locates the 6 o'clock position of the housing. Make sure it is engaged properly. Done right, it will allow only minor movement laterally (rotationally). Fasten strap to tighten completely.
6.) Often overlooked. If your battery had boiled due to a failed regulator, I wouldn't just add water and re-install. The car's electrical system is meant to keep the battery "at charge", it wasn't meant to get it there from a low condition. This puts undue strain on your electrical system. Better, to trickle charge your battery while it's out of the car ( while you're doing the repair), and put it back-in fully charged and ready to go.
Hope all this might help someone!
Wil Ferch- 85 Carrera
Addendum: With all the thought I gave to writing this, I noticed that I forgot to mention the usefulness of a small, "ignition wrench" set sold by Sears/Craftsman. These physically small wrenches really helped in the tight nether regions of the area.