Alternator sway help please!

DohertyCM · DohertyCM's Garage

I have an alternator light on....I just had it rebuilt last year and it doesnet have that much time on it.

With the MSD ignition and coil in the car I feel that it is causing the problem because of the draw on the system.

What I would like to do is upgrade the alternator, but I have found that the new alternators will not fit into my 74 housing..

I currently have the 2.7 motor with the 70 amp motorola alternator..

Vertex has started selling a replacement housing with the part number 93010600600R-which comes up as a 1980-83 911 housing....Will this fit my 2.7 motor using my existing 11 blade fan?
Will the pulley line up with crank pulley?

If not what are the alternatives....

What have other people done...

need answers quick - i have to do the upgrade so I can drive in my DE at the end of the month!

Chris

Laneco · 05-04-2008, 11:30 AM

I know this answer will make the concours guys scream - but here goes...

In my little budget coupe - Butters - I have a 1981 911 CIS engine with a 1976 fan housing. The 1981 housing was horribly cracked and unuseable. I'm using the 1981 eleven blade fan and alternator within the 76 fan housing. I pulled the engine out of the 76 myself and the fan assembly off the engine myself - absolutely no chance that it is anything but what I described above.

It fits. It works. Zero issues. Picture enclosed.

p.s. Alot of people have complained about the Vertex units on this website. I've never seen one or used one so I cannot comment on the validity of the voiced complaints.

angela

vash · vash's Garage

i am only guessing, but i dont think your MSD is pulling so much more juice than the stock CDI box. i have had mine in there for years, and no issues. did you measure voltage at the battery? what did you get?

not unheard of, for a rebuilt unit to die early. it happens.

vash · vash's Garage

i am only guessing, but i dont think your MSD is pulling so much more juice than the stock CDI box. i have had mine in there for years, and no issues. did you measure voltage at the battery? what did you get?

not unheard of, for a rebuilt unit to die early. it happens.

RoninLB · 05-04-2008, 02:05 PM

MSD text says 1Amp/1,000 rpm for all 6 series except HVC 6.

DohertyCM · DohertyCM's Garage

Well, I wonder why the alternator is going bad because I just had it rebuilt last year and I only have about 20 hours of use on the car..

willf · 05-05-2008, 02:30 PM

Chris, Did you mean motorola internal voltage regulator? How is the battery in the car doing? If the battery is good and holds a charge well, than I would have the alternator bench tested to see if all is OK. Considering the low hours and recent rebuild, it may be as simple as the voltage regulator going bad or being inconsistent. You should be able to test with the VR on the car by watching the voltage output while at idle and while the car is being driven. BTW, inconsistent VR was the problem with mine; replaced it and all is well. Let us know what you find.

DohertyCM · DohertyCM's Garage

Yes I checked the voltage at the battery at 3500 rpm and I was only getting 11.69 volts....I should have been around 13 volts... And it is an external voltage regulator...I also tried the troubleshoot procedures that are here on pelican parts and it appears that the regulator has crapped out..

I was reading the technical bulletin on the conversion of the external motorola type alternator to the internal alternator with a part number of 91160312004.

Has anyone done this? Can anyone tell me if that alternator will fit my fan housing with a part number of 9011061015R... Help

I dont want to spent 600 bucks on this conversion to find out that the alternator will not fit the fan housing...that would suck...

"Alternator Sway"....I have no idea on how that got into the title..

RoninLB · 05-05-2008, 05:34 PM

alternator upgrade

DohertyCM · DohertyCM's Garage

I read the bulletin as you posted, I was wondering if anyone has actually done this and if there were any "lessons learned" for this. I didnt want to make the investment and get burned on something because I didnt ask the right question.

I am so glad we have these forums.

RoninLB · 05-06-2008, 11:15 AM

confirm that the main red wire connector at the alternator and starter is in good shape. Add some solder if possible.

I used 8 gauge wire for the alternator ground to engine case.

clean all wire connectors and use dielectric at connections. Might as well clean and dielectric the connectors in the 14 pin engine compartment plug. I use a razor blade to widen the male pins for a tighter connection. They all have a slot for this.

I used a Valeo alternator and it didn't require the added resistor for the idiot light. I suggest a brand new alternator. Confirm that new alternator comes with the fan nut.

I used never-seize on the fan nut threads.

I've found that tightening all those pia small bolts around the alternator attached air distributor somehow affects the fan alignment in the housing. In other words don't flip if the fan rubs the housing. It's also easy to over tighten them and crack the air distributor.

it's a simple upgrade

DohertyCM · DohertyCM's Garage

Thanks for the info and reassurance. I will do everything you suggested.

Now off to find a valeo alternator.

Chris

Howard M · 05-07-2008, 07:27 AM

Why is the internal regular considered an "upgrade"? Wouldn't the remote regulator assist testing and replacement? Is the remote regulator still available? My OEM remote regulator and alternator are still on duty after 103K miles.

vash · vash's Garage

Quote:

Originally Posted by Howard M

Why is the internal regular considered an "upgrade"? Wouldn't the remote regulator assist testing and replacement? Is the remote regulator still available? My OEM remote regulator and alternator are still on duty after 103K miles.

+1

RoninLB · 05-07-2008, 08:00 AM

personally...

I'd consider the external regulator a stronger system.

The mechanical regulator isn't as electrically clean but I'm not running any multiplex computer control systems so it doesn't matter to me. Some say the internal regulator is heat sensitive. Seems that holds among track guys who come in with a hot engine and then shut down without cooling it down. I've never had a problem with an internal regulator. I also spend time cooling the engine down after running in 110F deserts.

AFAI know many auto guys have had trouble with the transistor external regulators. If I was using one I'd get an appropriate marine unit. It has to be selected carefully because marine charging systems can be very different than a car's.

Internal regulator/alternator are probably much cheaper for the factory?

47silver · 47silver's Garage

i am going through this now. i recommend rebuilding the alternator that is in the car. no matter what it costs.

Wil Ferch · 08-15-2008, 06:54 AM

11.69 volts at 3500 RPM?.........

For Reference...a fully charge battery is 12.6 volts
a 75% charged battery shows 12.4 volts
a 50% chaged battery shows 12.2 volts
a 25%% charged battery shows 12.0 volts

Anything under 12 volts is a "flat" /dead battery.....

DohertyCM · DohertyCM's Garage

You are not measuring the battery, you are reading the voltage from the alternator to charge the battery. The alternator should have enough voltage to run the car and charge the battery. Battery voltage was fine.

I have since bought 2 motorola (rebuilt) alternators off of ebay for 60 bucks each and the first one is still in the car and works great.

47silver · 47silver's Garage

I recommend rebuilding only because the case mates perfectly and the wiring is original.