Acceptable voltage range 3.2

[Poopwink]

Hi all,

I spent the weekend ripping around in my '85 Carrera and have a few questions for the more experienced owners on here.

On a few occasions, when I blipped the throttle to downshift, I heard a loud shriek from one of the belts. It does not occur EACH time I rev-match, and I cannot replicate it when the car is actually in gear.

I picked up this voltage meter/battery monitor a while back and popped it in as an afterthought as I was on my way back through town. The reading would swing as I applied or backed off the throttle but I'm worried about acceptable readings? At times the meter read as high as 18v and other times it dropped below 12v. Is it dangerous to have the voltage spike so high?

The fan belt doens't look worn or frayed, and there isn't a worrying amount of slack, but it seems likely that these two things are related. I have the original tool roll including the fan pulley holder tool. It would also be helpful to understand what range is considered "safe" for the electrical system. Thanks in advance.

[jlex]

How long was it at 18V? I've seen mine touch 15 before, but it's nearly always around 14. Does your battery show any damage such as leaking acid? Keep a good eye on things.... you may need a new voltage regulator.
I'd check volts at the battery using a multimeter as those cigar lighter units can be a bit wonky.

[darrin]

18 volts is (imo) too high to drive until fixed -- check under/around battery for evidence of boiling over and have alternator/voltage regulator rebuilt -- should be an old-school shop in/around Portlandia

you could confirm it's not the gauge by testing it in another (newer) car

[Noah930]

I wouldn't feel comfortable with the car voltage spiking to 18 v either. Spikes are better than sustained and/or frequently elevated voltage. But I 'd always be worried that I could fry something.

[86 911 Targa]

Looks like a voltage regelator issue.
Have the the VR tested under load.
Should be around 14.2V

Best,
Gerry

[ClickClickBoom]

Stop, do not start or drive, there are sensitive capacitors in different components and they are rated at 16v. At 18v stuff starts to sizzle along with the battery. Replace/rebuild the alternator. Stat!

[GH85Carrera]

Originally Posted by ClickClickBoom

Stop, do not start or drive, there are sensitive capacitors in different components and they are rated at 16v. At 18v stuff starts to sizzle along with the battery. Replace/rebuild the alternator. Stat!

This. Have a local shop rebuild it, and be sure they put in new bearings. You will have a perfectly working alternator for another 100,000 miles and it will 100% be the right wiring and easy to reinstall.

[Poopwink]

Originally Posted by jlex

How long was it at 18V? I've seen mine touch 15 before, but it's nearly always around 14. Does your battery show any damage such as leaking acid?

The meter didn't remain at 18v for any more than a second at a time. The readout changed pretty much constantly as long as the vehicle was in motion. I couldn't find any evidence that battery boiled over. I disconnected the battery briefly as soon as I got home and didn't find any leaks or acid damage.

From what I understand, best course of action for the alternator is to remove it and bring it to a shop that specializes in alternator repair/rebuilds. It would be great to find someone who's worked on Porsche units previously but the consensus seems to be it's not a must-have. I'd be grateful for recommendations in the Portland/Vancouver WA area if anyone has recent experience.

Originally Posted by jlex

Keep a good eye on things.... you may need a new voltage regulator.
I'd check volts at the battery using a multimeter as those cigar lighter units can be a bit wonky.

Is the voltage regulator considered part of the alternator rebuild or is that something I'd need to replace separately? I'm unsure if the voltage regulator is something that could get repaired/rebuilt at an alternator shop.

[GH85Carrera]

I believe that most if not all 3.2s came with an alternator and internal voltage regulator.

[proporsche]

Get yourself voltage regulator..once you are at it have a look at the rotor where the brushes ride..If still ok just replace it and you`ll be ok

or take a picture of the rotor and show it to us here...

Ivan

[Trackrash]

Originally Posted by GH85Carrera

I believe that most if not all 3.2s came with an alternator and internal voltage regulator.

Yes. Since '82

[ClickClickBoom]

Originally Posted by Poopwink

The meter didn't remain at 18v for any more than a second at a time. The readout changed pretty much constantly as long as the vehicle was in motion. I couldn't find any evidence that battery boiled over. I disconnected the battery briefly as soon as I got home and didn't find any leaks or acid damage.

From what I understand, best course of action for the alternator is to remove it and bring it to a shop that specializes in alternator repair/rebuilds. It would be great to find someone who's worked on Porsche units previously but the consensus seems to be it's not a must-have. I'd be grateful for recommendations in the Portland/Vancouver WA area if anyone has recent experience.



Is the voltage regulator considered part of the alternator rebuild or is that something I'd need to replace separately? I'm unsure if the voltage regulator is something that could get repaired/rebuilt at an alternator shop.

Make sure you tell the 40 year old capacitors that it was only as second or two. Ask John Walker where he would go, if not with him. The R&R of the alternator is a given, its either do that or drive and replace the Tach, DME and a potentially long list of other components. Alternator tech is solid 1960s technology, find an Auto Electric shop that does alternators and starters. Semi rural areas have the best chances, since farmers have the oldest stuff known to DaVinci.
I replaced my alt with a modern alternator from Classic Retrofits:
https://www.classicretrofit.com/collections/upgraded-alternators
I also added a Clewett pulley system:
Clewett Alternator/Crank pulleys
The 911 series alternator is the same basic design from the 60-70s. The Classic Retrofit brings a modern design to the table, check out the sites/threads. Having a modern alternator and pulley system brings my 911 solidly into the 1990s. Was it cheap, nope, but when compared to the high amp alternators for race trucks and sports cars, the price was in line with low production volume custom parts, same with the pulley system, its a beautiful piece of CNC machine work and is worthy of being buried on the back of a 911.
BTW my alternator runs amazingly consistent 13.9-14.1 temperature dependent. Check the voltage at an RPM above idle, say 1500 RPM. The Classic Retrofit puts out a whopping 175a at rated RPM, while my amp schedule will never get anywhere near that, having a system the for all intents and purposes is constantly "idling" along at any possible load.

[jlex]

Must mean 13.9 - 14.1....

[rw229]

I've been though this with several 80's 911s. Don't bother with just the voltage regulator, replace or have a quality rebuild of the alternator ASAP. As mentioned above, many components are at risk. I've ruined batteries, clocks and a tach due to voltage spikes.

[fred cook]

The high voltage reading on my 1980 SC is about 13.8 volts. With the engine/ignition off, the battery reads 12.5 volts. I get essentially the same numbers on my 1994 Jaguar XJS so they appear to be in the realm of normal! The high voltage reading on my 2014 Ford F150 is usually 14.2 volts.

[Hotshot]

I am always looking at my voltage. 14.2-13.9 normally with nothing on. I had it go to 15.1 once and my radio was tripping out. Turned out to be some old grounds. Check door light contacts. Also check off your battery too.

[kanadary]

Mine is between 13.8-14.2.

[fallingat120mph]

1986 Coupe here...Going through all things electrical and here is where I am:

Battery Cold: 12.7
Car started at idle: 14.1 - 14.0
Car at 2000 rpm: 14.3
Car at 2000 rpm w/lights: 13.9


Just took the car out for an hour and voltmeter in dash read 14.0 pretty much steady with lights on.

With the lights off meter read 14.3 while driving.


This car has over 200,000 miles on it and comes from a humid background (if that matters).

14 and above seems high to me...just not finding a definitive answer. I have no issue with pulling the alternator and rebuilding - it is very old and very used.



Hopefully resurrecting a thread from 2020 isn't too taboo here


Thanks!
Erik

[rw229]

I don’t remember the factory spec, but 14 doesn’t seem outrageous. The risk would be any spikes as the electronics in these cars are old and not very robust. If concerned, I would check your grounds and have a quality rebuild done on the alternator… or replacement, but I think that is big bucks now.

[Hotshot]

After all grounds changed and new VR, 13.8-14.5 nothing on. Above 2000, 14.3-4 for the most part. Only counts over 2000rpm. Load up the fogs and ac at night and idle is 11.9-12.0 until 2000. Book says same.