73.5 Voltage regulator wiring

[rockreid]

The 73.5 is a special alternator/VR wiring unique to this model that has a special add-on wiring diagram. I updated my alternator and VR to Bosch. They were Marchal.

This add-on wiring diagram does not address which wire goes to the VF terminal on the VR. It says the relay 86 Black wire should go to the D+ on the VR. The Brown relay 85 wire should go to D- (Ground).

I currently have the original Blue spade wires plus the Black spade pig-tail going to D+ on the VR. The other Black wire (which was a loop terminal on the Marchal VR) is now going to the VF terminal on my Bosch VR. The two Brown wires are still grounded to the chassis behind the VR. I am leaving the VR D- terminal not connected.

I have no way to test to see if this is correct right now as my fuel distributor is being rebuilt. I would like to know if my setup should work when I do fire up the engine in a few weeks.

Anyone with a 73.5 Bosch- updated alternator setup verify this is correct?

[E Sully]

The wiring for the '73.5 voltage regulator DF wire just goes from the alternator to the regulator as shown in the standard wiring diagram. The diagrams don't show the noise suppression capacitors though. The only difference is the 2 wires shown in the CIS additional wiring diagram which as you stated go to D+ and D-.

[rockreid]

OK, no wonder I'm getting confused as my project 73.5 does not have those capacitors anymore..No idea when they were removed. As a result my wiring is off from the diagrams. Looks like I may have to wire straight from the alternator just to make sure I'm good.

[timmy2]

Your 14 pin connector from the engine harness has the 3 remote VR wires in it. Pins 11, 12 and 13 IIRC. From there it goes to the VR and the blue wire D+ also goes to the second 14 pin connector and from there to the alt light on the gauge.
Black is DF, blue is D+, Brown is ground.(D-).
The capacitors were for radio noise suppression.


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[db_cooper]

I vaguely remember an update service bulletin from Porsche concerning the alternator/voltage regulator on the 73.5 and will try and find it.

I recall the replacement alternators had an internal regulator and the external voltage regulator was discarded or left in place but out of the charging circuit..the reason was all the Porsche alternators had internal regulators as a replacement part. The service bulletin described the rewiring needed to make the change.

My point being you may have an external VR...but if the alternator has the internal VR..the old external VR is there just for show.

[RSTarga]

Do you have a picture of tha back of your replacent alternator?

[db_cooper]

Found the Porsche Product Circular #82-02 Group 27 for 911 dated February 12, 1982.

If you want I will try and upload the document.

A quick way to tell if your alternator has been changed..the instructions refer to "cutting the DF wire (black)" on the wiring harness behind the alternator under the fan shroud.

If you check the DF (black) wire at the VR with an ohm meter and it is an open circuit..the DF wire may have been severed when a new style alternator was installed.

There is a note on the PC #82-02..Only the new type alternator (internal VR) will be available for replacement after existing stocks of the old version are used up.

[db_cooper]

Originally Posted by rockreid

OK, no wonder I'm getting confused as my project 73.5 does not have those capacitors anymore..No idea when they were removed. As a result my wiring is off from the diagrams. Looks like I may have to wire straight from the alternator just to make sure I'm good.

I think those capacitors were part of a CIS service kit (in the days prior to recalls being done) Porsche used on the first CIS 911s because of blown air boxes.

The idea was to prevent accidental firing of the CD box-spark plugs when turning the ignition key on, rather than ignition noise suppression.

The kit included new spark plug wires with the braided steel grounds on the fan housing too.

There were some other bits included..sorry I don't recall.

[E Sully]

The question now, is it externally regulated Bosch, or internally regulated.
Of course it would change things if an internally regulated alternator was used. In this thread I posted that update information.
Fan shroud, searched really.

As for the capacitors, you can see them in the picture of my console above. There are capacitors mounted above and below my regulator. I believe these 2 were for the radio suppression. You can see the top of the CDI capacitor behind the black relay on the left. I don't know if this was for CIS or radio suppression, as db_cooper suggested.

If internally regulated, some wiring would be needed to power the relay for the WUR that was originally connected to the external regulator.