Charging problem

[Ozark]

My first post on this forum. I'm a long time 356 owner but new to the 911 with my recently acquired 1986 3.2 coupe with over 300k miles and sadly no maintenance records. It's a beater but runs strong and I plan to drive it like I stole it, which I practically did (kin folk deal). I'm slowly sorting through it and have an electrical problem which requires advice.

I suspect an alternator and/or voltage regulator problem. When I first drove it in mid-July it died at my first fill-up. I jumped it, drove 60 miles home, and charged the low battery I installed one of those cheap cigarette lighter volt meters and noticed the voltage was erratic, jumping from 17.2 to 14 to 9.6 and suspected the VR. Battery died again. I checked grounds, replaced the corroded battery strap with a new cable and removed, cleaned and reinstalled most of the others (except the alternator ground). That seemed to fix it - for awhile. Then it no longer jumped above about 14.2 but gradually dropped to 9.4. After a 3 hour drive today it fell from 13.4 to 9.4 but then suddenly rose to 13.4 just as I got home! I parked it and checked running voltage at the battery at 11.4.

The warning light comes on with the key but does not light when running, even at low voltage.

I'm ready to pull the alternator and take it in for a rebuild, with a new VR. Does that sound like the logical next step?

This forum is a wealth of information and I appreciate the free flow of information. I hope I can add to the flow at some point.

Thanks!
Gordon
NW Arkansas

[Cairo94507]

I think you hit all of the typical issues- mostly being bad grounds. Next step you are considering is what I would do. I too would not buy a rebuilt unit, I would find a shop to rebuild your alternator. Good luck.

[T77911S]

drive to a place like advance auto and let them check it for FREEEEEE!!

sounds electrical/connection but how old is the battery.
are the battery connections clean

[GH85Carrera]

Most likely the voltage regulator is internal to the alternator. Check all the grounds, especially the transmission to body ground. If it still does not charge, pull the alternator and take it to a local rebuild shop. Let them do a full rebuild, and check up. Then you know you have a good alternator. With no records, start with that as a solid fix and document it.

[Robey5]

Sorry to hijack the thread; But if you have a “not good” ground; be it at the trans or such: would that not enable to alternator to re-charge the battery whilst driving? Would this “condition” also promote the idea of killing the battery between drives?

This all is hypothetical to me, but: I have a brand new AGM battery (swapped after the other one was dead between 2 days), and the cig-lighter volt meter shows around 14.1V after start, and I disconnect the negative cable after every drive regardless of distance.

To the OP, before considering a new/rebuilt alternator: I would suggest pulling it and bringing it to the zone to test it; or find a starter/alternator rebuild shop nearby to test it.

[Ozark]

Thanks for the feedback. The battery is just a year old. The only ground I have not checked is the one from alternator-to-engine, which I'll check when I remove the alternator. Once I'm that far along I'll take the alternator into the rebuilder and they will bench test it.

I'll report back with results.

Gordon

[GH85Carrera]

Originally Posted by Ozark

Thanks for the feedback. The battery is just a year old. The only ground I have not checked is the one from alternator-to-engine, which I'll check when I remove the alternator. Once I'm that far along I'll take the alternator into the rebuilder and they will bench test it.

I'll report back with results.

Gordon

That is a for sure "while you are in there" moment. With no history on the maintenance of the car, unless the alternator just look new, I would have them do a full rebuild. New bearings and brushes and anything else to make it like new.

It is not a simple chore to R&R the alternator. Personally I would rather KNOW it is 100% and solid. For my 1986 El Camino alternator, I can swap the alternator in 15 minutes. I would just check it and if good at all, put it back on since it is so easy. Not so with the 911.

[kltarga72]

Originally Posted by Robey5

Sorry to hijack the thread; But if you have a “not good” ground; be it at the trans or such: would that not enable to alternator to re-charge the battery whilst driving? Would this “condition” also promote the idea of killing the battery between drives?

This all is hypothetical to me, but: I have a brand new AGM battery (swapped after the other one was dead between 2 days), and the cig-lighter volt meter shows around 14.1V after start, and I disconnect the negative cable after every drive regardless of distance.

To the OP, before considering a new/rebuilt alternator: I would suggest pulling it and bringing it to the zone to test it; or find a starter/alternator rebuild shop nearby to test it.

Current needs to flow in a circuit such as a 12vdc circuit from battery positive to negative ground. The alternator recharges the battery while driving but if there is a corroded ground return (loose or dirty) anywhere in the circuit you will increase resiistance. Ohms law states when resistance increases current decreases.
E=IxR
Always important on any old vehicle to keep ground connections clean. Corroded grounds will cause a lot of intermittent or erratic electrical gremlins.

[911obgyn]

If you are in a damp climate use a bit of silicone grease, or dielectric grease on your grounds to keep them from corrosion.
When you pull the alternator take a picture before you remove the connections and on a 300k car consider replacing the charging wire to the starter, it may be crispy. Before you pull the alternator you might want to wrap your arms around the transmission and check the connection at the starter.
Just to get to know her a little better

[Artfrombama]

I burned up two alternators before I discovered a corroded ground from my VR.

[Ozark]

I pulled the alternator and while disassembling it I discovered what looks to be significant damage to the fan shroud. One of the blade shaped "legs" has cracks front and back. I also found that the fan blades had been rubbing on one spot of the shroud. Not much but enough to leave a mark on the shroud and shine up the fan blade ends. Could that broken shroud cause the rubbing? See photos. Is that shroud repairable or am I better off to replace it? Suggestions on sources?

TIA.

Gordon

[Artfrombama]

I believe I would replace that broken fan housing. Is that a magnesium part? Looks like it was dropped or burned??

Originally Posted by Ozark

Suggestions on sources?

TIA.

Gordon

Check the Pelican 911 parts classified, post a WTB

[Ozark]

Someone please correct me if I'm wrong but according to the casting #930.106.102.3R, equals P/N 903.106.102.07, which was superseded to 903.106.006.07, which should be magnesium.

Considering there are several other more minor cracks I think replacement is called for. I see that replacements are available in aluminum which I assume would be less brittle and the better choice? Prices - $600-$850 ouch!

Gordon

[LIRS6]

That shroud could well be the cause of the rubbing, as the break in the support probably means that the alternator housing is off-center. Do a search, there is/are people on the forum who make repairs to our shrouds but the damage you have may be unrepairable.

Good luck.

Jason

[john walker's workshop]

Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8 has been known to weld those things. Wouldn't hurt to ask. He's in 'bama.

[Ozark]

Thanks John. I'll check it out.

Gordon

[Ozark]

On cleaning and closer inspection I found several other cracks in the housing. Brian recommended replacement due to the likelihood of general deterioration of the metal. I placed a WTB in the classifieds but I see several others looking for the same so a repro may be in order. Any experience with the Carpoint unit?

Guess I'll file this in the one-thing-leads-to-another category.

Still waiting to hear from the shop about alternator repair.

Gordon

[Porsche 2]

I have a late 1970's rebuilt alternator (same as SC) that I replaced with a WOS 170 amp alternator to drive my electric AC compressor. The available alternator has new bearings, voltage regulator and diodes which generated 14 volts at any engine speed above 1100rpm - correct performance. Yours for $200 plus shipping from S. Cal.

[Ozark]

Thanks for the offer Porsche 2. I'm still waiting to back from the shop about mine. If it turns out to be an expensive repair I'll take you up on it.

[john walker's workshop]

You can have an early, shallow depth housing machined to carrera depth at your local machine shop, if one turns up.