SWB - 901/05 Alternator options Early cars

[Mighty2.0]

Hi early 9 crew ,

OK so I've searched and searched, but I can't located the ultimate solution.

My 1966 911 2.0 (304093) has a different alternator, with an internal regulator. The original external regulator is still in place, but the wiring to the alt. has been re-configured for the newer style alternator. There are no names or numbers on the unit, as I remember.

Alternator light glows faintly when headlights are on, and glows brighter when brake pedal is pressed.

Battery is a lead acid Interstate MT51R (2001, old -planning to replace anyway).
I measure about 12.6 volts at the battery, at idle, with headlights on.

My headlights are Hella Vision Plus inside original Hella glass covers, H4 bulbs 60W low x 100W high. Connections look ok, I cleaned the grounds I could find.

Should I upgrade to the 95 amp alternator "rugged, designed to perform" ? ($700- very pricey)
How about the 55 amp (1972-), with external regulator?

I want brighter headlights, and I'd like to have the external regulator working again, mostly for looks. I hate having a live wire not connected - right now it is taped off to keep the weather out.

What are the pros, cons. I've heard the 95 amp won't fit my orig. fan housing. Is this correct?

1. What are my options, to keep an external regulator?
2. What's the best version to upgrade to a newer style w/o regulator?
3. Which route do you recommend?

Any help is appreciated, thanks.

[Mighty2.0]

Anybody?

[304065]

Mitch, long time. How's the '66?

Here's the photo I snapped of your '66 back at the Parade.



You can see that you have a later fan shroud that was designed to work with the later alternator with the internal regulator. The fan is a 930 type, you can see the slots around the hub, and there is a small diameter pulley installed.

To be original, you need a 250mm fan housing and fan. These are available from time to time, they aren't cheap but you can find them here. I would look very carefully at the back of the fan, these often corrode badly inside. The good news is that your current setup has value.

Now, it comes down to whether you use the 35A vs 55A alternator. I think they are basically the same body, but with uprated diodes inside, and the regulator attachment is slightly different (two right-angle pins instead of studs) but no reason not to use it, particularly given the current consumers you propose.

Vintage Bosch Starter and Alternator Rebuild - Early 911S Registry Bulletin Board

Your early VR is probably electromechanical-- you can see what it should look like in this thread:

Before there was BHKZ: SWB engine electrics

For the 55A for "road" use you can use a modern, solid-state Bosch VR that looks very, very similar to the original. The entire electrical panel can be swapped for show purposes if you are so inclined.

I have gone back and forth on the issue and don't think much of internal regulators. The internal VR is two inches from the engine case and there's no airflow when the engine shuts off. HEAT is the enemy of electrical components and the VR is no exception. I think it's far better positioned over on the electrical console away from heat. It would be even better out of the compartment entirely, but that's only an option for Race Cars.

Good call on the Vision Plus, they are DOT-legal H4. I have a pair of the same ready to go in 304065 when the assembly process begins.

Hope this helps! Good luck.

[Mighty2.0]

Hi John,
Thanks for responding.
I was really hoping for a solution that would fit my current housing and fan, since the cost of a new 901 fan is roughly $900, plus whatever a used housing would cost.

I replaced the original fan because it was cracked (see photo). I think this was caused by a loose engine tin bolt, which I discovered soon after I bought the car!

Is there an alternator w/ external VR that will fit my current housing, so that the car will at least look original?

Is it possible for an auto-electric shop to upgrade an alternator's output from 35 amp to 55 amp? Is it just a matter of swapping out diodes or parts?

Take a look at the gap between my engine shroud and my housing.
Is this because my housing is too small, not compatible w/ the shroud? At first I thought the shroud was warped from heat.

The part number on the housing is 901 106 101 5R - what model/era is this for?

I noticed the PET on Porsche's website does not cover the early cars (1965-1968). Do you happen to have this in pdf that you could send me?

As always thanks for your help- anyone else is welcome to chime in here.

[WANNA930]

Try DaveBarton.com. He makes a kit to use an external VR of internal VR alternators. I just bought a adjustable ext VR from him and the service was great and shipping super fast.

I have a stock 71e and at idle it would dip into the low 12's with lights on. I have VR set at 14.25 which was a random test number and now I have high 12's low 13's at idle. If it just needed a new VR to begin with???

I rigged an Gauge and watched my volts in relation to engine speed. It seams that below 1000RPM they just aren't at full output. Once past 1000 at 1200 and higher I am at almost full 14.25. I am Hot Rod guy and wonder if a pulley change would get alt spinning faster at lower engine RPM to eliminate low volts below 1000 rpm. It also seams to hang a bit once rev'd a couple times. Not big electrical guy so there also may be a way to get it in faster electrically?


Good luck and tell Dave Brian sent you!!

[304065]

Here is the list of fan housings by year, thanks to Tom Butler


1. Early 250 mm Al sand cast shroud ring (no coil studs) 1965-'67.5 - Casting # 901.106.101.03
2. Early 245 mm Al die cast shroud ring (no coil studs) 1967.5 - Casting # 901.106.101.0R
3. Later 245 mm Mag die cast shroud ring 1967.5-'77 - Casting # 901.106.101.5R
4. Early SC 225 mm Al die cast shroud ring 1978-'79 - Casting # 930.106.101.0R
5. Late SC 245 mm Al die cast shroud ring 1980-'83 - Casting # 930.106.102.0R
6. 3.2 Carrera 245 mm Al die cast shroud ring 1984-'89 - Casting # 930.106.102.4R
7. 3.3 Turbo 245mm Al die cast shroud ring casting # 930.106.667.4R

So you can see, you have a mag housing from a later car. It's important to note that all these housings were meant for use with an externally regulated alternator-- you probably have a Motorola in there that has been converted with an internal regulator.

That original fan can be welded up. Send it to Ollies (they moved to Lake Havasu, AZ) and they can fix it up, I see two blades that are broken.

New fan? Forget about it, nobody buys a new one. I have seen used 250mm fan, housing and alternator for sale for around $500 in the classifieds here.

Send me a PM with your email address, I can probably help you out with an alternator. I don't think parts are available to upgrade the 35A, you'd have to buy a 55A in the first place. You can probably buy a 55A for around $100 and have it rebuilt for another $100 and have good, cheap, reliable power for everything. Well, maybe not hood-mounted Cibie 100W. . .

[Mighty2.0]

Thanks for the facts John - I knew you would have the info. You're the best, man.

[Neil '67 911S]

John;

Being very electrically challenged, I'm confused by some of your comments in this thread. I'm not clear whether it is possible to simply "plug and play" a 55 amp Bosch alternator into a SWB. In this case, Ol' Ivory (Sept. '66 911S).

You mention that the 35 amp alternator has an internal regulator and that the 55 amp unit does not but there's a voltage regulator mounted on the stock electrical panel, left side of the engine compartment.

If I need to change out the stock electrical panel, then I'm inclined to stick with the stock 35 amp alternator.

Thanks in advance!

[304065]

Originally Posted by Neil '67 911S

John;

Being very electrically challenged, I'm confused by some of your comments in this thread. I'm not clear whether it is possible to simply "plug and play" a 55 amp Bosch alternator into a SWB. In this case, Ol' Ivory (Sept. '66 911S).

You mention that the 35 amp alternator has an internal regulator and that the 55 amp unit does not but there's a voltage regulator mounted on the stock electrical panel, left side of the engine compartment.

If I need to change out the stock electrical panel, then I'm inclined to stick with the stock 35 amp alternator.

Thanks in advance!

Neil,

I don't remember ever having said that either a 35 or a 55 amp alternator has an internal regulator. I said that I think Mitch's alternator has an internal reg, but it's probably one from a much later car that matches his much later fan housing, incorrect for a '66.

If you use either the 35 or the 55 amp you can stick with your existing electrical console. The modern solid-state voltage regulator (external) is the same for both alternators. The 55 has a different connection for the DF and D+/61 wires, but it's a pretty simple matter to modify the harness to work. You need to change out one ring terminal (on D+/61, the "blue wire) for a 1/4" faston-- the DF wire already has one on it from the factory. Insulating them isn't a bad idea either.

The real issue is this: actually trying to carry 55 amps into the car from the B+. OK, you can use a heavy ground strap between the engine case and D-, that takes care of the ground half. For the positive half of the circuit, it's another story.

Remember that the early cars carried the B+ current through a 10AWG (not exactly, it's a metric wire but 10AWG is as close as we have these days) red/white wire over to the electrical console, where it joined up on the junction block with the wire to the car's main harness. So charging of the battery was handled through that little 10AWG wire.

On the "modern" cars like the SC there is a separate wire that runs from the alternator B+ down through a grommet in the engine tin, to the Starter 30 terminal. That's a much better way to get current to the battery. The size is listed as "10" on the diagram, that is 10mm^2 or 8 AWG.

8 AWG has a max current of 73 amps in chassis wiring, that is a 33% safety margin over the 55 amps of the 10AWG.

So, long story short, you can install the 55A alternator in the car, but it will take some wiring modifications to make it work, and to really optimize the power output. The 55A is heavier also. I'm using a 35A for concours.

[Neil '67 911S]

John,

Many thanks for your concise explanation. I've decided to stick with the 35 amp unit.

For those interested in having their starter or alternator rebuilt, Mark Lecome (not Matt) is still in business. I dropped a couple of alternators off at his house yesterday and had a nice chat with him. You described him in this link.

Vintage Bosch Starter and Alternator Rebuild

For those out there who tried and failed to get in touch with him, he was using Vonage for his phone, which evidently failed and he also let his website lapse. He's actually in New Bedford, MA but because of zoning, he has to have a PO box in Freetown. He can be reached at 508-995-3755

For those of you with a taste for the older rigs, Mark will also rebuild Bosch generators. He/his shop is a certified Bosch repair facility.