Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > Porsche 911 Technical Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Tired Member
 
DaddyGlenn's Avatar
 
Join Date: Dec 2004
Location: Pittsburgh
Posts: 2,308
Garage
Alternator stops charging

I’ve done a search but did not find anything helpful. I’m sure it’s out there, just can’t find it.

Here is my situation. 1978 911sc, battery is a couple years old, alternator is much older (12 years w/internal regulator). I drove from Pittsburgh to Indianapolis without a problem, then on to St. Louis the next day. Still no problem. The car sat in STL for a few days while I attended a conference and fired right up on Thursday morning when I headed to Florida.

In the afternoon I stopped at a rest stop in north Georgia and there wasn’t enough battery to start it back up. Multimeter showed just under 10 volts at the battery. I found the battery negative ground wire was a tad loose and tightened it up. AAA was called and 3 hours later, got the car jumpstarted. I drove to a nearby auto parts store and had the battery tested. Battery was good but needed a charge.

It was only about 15 minutes of driving to get to the auto parts store but the battery had enough juice to start the car without any problem. I drove another 15 minutes and stopped for the night. Hoping the problem was the loose wire.

The next morning, the battery was showing 11.8 volts and the car started easily. I continued south. Shortly after crossing into Florida, my radio would not stay turned on. This had happened the prior day before I found the issue. So I took it as a sign the electrical issue was back. I powered off the vent fan and unplugged my phone from the charger to save power. With a lot of drafting of 18 wheelers, I stretched that tank of gas and made it to my destination (Melbourne, FL) 3 hours later.

Generator light only came on when first starting the car. Other than the radio not staying on and my phone not charging like normal, there were no indications of a problem. I can only correlate the issue with running duration of 4-5 hours and heat. Both days were cool in the morning when I started out but got really hot.

Question ... is the alternator failing when it is hot, a typical failure mode?

I have ordered a rebuilt Bosch alternator to be delivered Monday and hope to be driving back to Pittsburgh on Tuesday. I just need to boost my confidence that replacing the alternator will solve the issue.
__________________
Glenn
Daily Driver - '78 911SC RoW, Track - '85.1 944
Wife's - '00 740iL (Sport),
Support vehicle - '00 Suburban 2500 4x4
Son's - '85.1 944

Last edited by DaddyGlenn; 10-06-2018 at 11:30 AM..
Old 10-06-2018, 06:56 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Registered User
 
woland's Avatar
 
Join Date: Jan 2010
Location: Ovaro - Carnic Alps - Italy
Posts: 173
Garage
Extremely hot and cold temperatures can affect the battery, not the alternator.
In case of alternator fail, red light stays
Had similar issue ten years ago all sudden, and simply replaced the brushes
Never again had problems with battery charge.

__________________
Paolo from Alps

1980 911 Targa SC 3.0 - Silver metallic
1980 Ducati Pantah 500 - Red
1989 Yamaha 500 "Tracker"
Old 10-06-2018, 07:22 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
76 911S Targa
 
Join Date: Oct 2010
Location: Idaho
Posts: 1,133
If you have a voltmeter, diagnose the problem by testing the battery voltage with the engine running. Should be about 14 volts if the alternator is working. If it is not charging, likely your 40 year old alternator needs repair.
__________________
76 911S, 2.7, Bursch Thermal Reactor Replacements, Smog Pump Removed, Magnecors, Silicone Valve Cover Gaskets, 11 Blade Fan, Carrera Oil Cooler, Turbo Tie Rods.
Old 10-06-2018, 07:43 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Registered User
 
Join Date: Jan 2014
Location: Jericho Vermont
Posts: 365
Garage
I start my cars turn every thing on fan lights etc. As it's running I disconnect the battery. If the car dies your alternator is in need of repair. 9 times out of 10 it's the module which contains the brushes and the regulator ~$70.00. 2 nuts to replace it.

The alternator should supply the necessary current to run the car without assistance from the battery. After the car starts the battery's function is a big capacitor.
__________________
AlfasRule!
72 Montreal (Da Pumpkin)
75 Alfetta Sedan, 75 Alfetta Coupe Race Car
82 Spider, 84 GTV-6. 84 GTV-6 Verde (GiGi)
87 Milano ( Da Winta Beata)
Old 10-06-2018, 07:54 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
ROW '78 911 Targa
 
timmy2's Avatar
 
Join Date: Jul 2011
Location: Salem, OR
Posts: 8,807
Garage
Check the battery voltage while running to see if the alternator is charging, 11.8 volts in the morning is possibly a failed or failing cell.
__________________
Dennis
Euro 1978 SC Targa, SSI's, Dansk 2/1, Bitz kit EFI.
Need a New Wiring Harness? PM or e-mail me. Search for "harnesses" in the classifieds.

Last edited by timmy2; 10-06-2018 at 08:13 AM..
Old 10-06-2018, 08:10 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Ubi bene ibi patria
 
Hawkeye's-911T's Avatar
 
Join Date: Jan 2007
Location: For the most part, in my garage.
Posts: 2,022
Garage
Quote:
I start my cars turn every thing on fan lights etc. As it's running I disconnect the battery. If the car dies your alternator is in need of repair.
I seem to recall reading somewhere if one disconnects the battery while the engine is running, you'll basically crater your alternator.
Is this factual or not? Maybe I could be misinterpreting a 'tongue-in-cheek' remark.

Cheers
JB
__________________
“Two possibilities exist: either we are alone in the Universe or we are not - both are equally terrifying” ― Arthur C. Clarke
Old 10-06-2018, 09:04 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Registered User
 
Join Date: Jun 2009
Location: victoria, BC
Posts: 21
Quote:
I seem to recall reading somewhere if one disconnects the battery while the engine is running, you'll basically crater your alternator.
I've read this too, on the colour wiring diagrams that our host used to host. In the lower right corner of the diagram, at least for my '68, it reads:

IMPORTANT -- Disconnecting of the battery with running engine results in immediate destruction of alternator.

Given that that's on the factory wiring diagram, I'd be inclined to believe it. I don't know if it applies to the more civilized SC, though, maybe their regulators are different.
Old 10-06-2018, 09:56 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Tired Member
 
DaddyGlenn's Avatar
 
Join Date: Dec 2004
Location: Pittsburgh
Posts: 2,308
Garage
Update:

Battery showing a little over 10 volts and will not start the car. Jump started it and measured 12.8 volts with car running at 2k rpm.

Rebuilt Bosch alternator is scheduled for delivery on Monday.

Based on comments above, I suppose a loose battery cable could have damaged the alternator.

If all goes well, I’ll be on the road to PGH on Tuesday.
__________________
Glenn
Daily Driver - '78 911SC RoW, Track - '85.1 944
Wife's - '00 740iL (Sport),
Support vehicle - '00 Suburban 2500 4x4
Son's - '85.1 944
Old 10-06-2018, 11:25 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Registered User
 
Join Date: Jan 2014
Location: Jericho Vermont
Posts: 365
Garage
It does not, it takes 1 second. If the alternator is malfunctioning it will stall immediately. No harm to anything. Running the car without the battery connected I understand, but this is only a test procedure I've used for decades, Old cars as well as new.
We all use pretty much use the same brand of alternator in both cars as well. Why mess with perfection?
__________________
AlfasRule!
72 Montreal (Da Pumpkin)
75 Alfetta Sedan, 75 Alfetta Coupe Race Car
82 Spider, 84 GTV-6. 84 GTV-6 Verde (GiGi)
87 Milano ( Da Winta Beata)
Old 10-06-2018, 12:21 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Registered User
 
midnight911's Avatar
 
Join Date: Apr 2007
Location: PDX, OR
Posts: 984
Garage
these are useful. i have them in my cars. my 911 started showing 12.x and 11.x volts. Indeed the brush was gone. replaced the VR and back at 14+V when running. some people also have these to monitor voltage surge which results in battery explosion.

https://www.amazon.com/s/ref=nb_sb_ss_i_1_13?url=search-alias%3Daps&field-keywords=volt+meter+cigarette+socket&sprefix=volt+meter+ci%2Caps%2C227&crid=1O6JBYDB6FMKQ
__________________
1984 911 Carrera Coupe - 32C #73 - M64/05
1998 E36 M3 4dr
1989 E30 325i 4dr
2006 Sienna 5dr - the hauler
2010 Cannondale Caffeine II - Lefty
Old 10-06-2018, 10:34 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
Registered User
 
Tori's Avatar
 
Join Date: Jul 2016
Location: Pismo Beach, CA.
Posts: 653
Quote:
Originally Posted by DaddyGlenn View Post
Update:

Battery showing a little over 10 volts and will not start the car. Jump started it and measured 12.8 volts with car running at 2k rpm.

Rebuilt Bosch alternator is scheduled for delivery on Monday.

Based on comments above, I suppose a loose battery cable could have damaged the alternator.

If all goes well, I’ll be on the road to PGH on Tuesday.

So how about an update buddy ???
__________________
1987 911 Carrera Coupe
1987 Buick Grand National
1971 Plymouth Roadrunner
Old 12-12-2018, 07:48 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)
Almost Done
 
Join Date: Mar 2015
Location: ontario canada
Posts: 1,009
Garage
did you by any chance change your dash bulbs, if so, your charging lamp may be a culprit as its not generating enough in the circuit to trigger the exciter?
Old 12-12-2018, 08:47 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #12 (permalink)
Registered User
 
Tori's Avatar
 
Join Date: Jul 2016
Location: Pismo Beach, CA.
Posts: 653
Quote:
Originally Posted by 7783911 View Post
did you by any chance change your dash bulbs, if so, your charging lamp may be a culprit as its not generating enough in the circuit to trigger the exciter?
Hold the phone..... is this a thing? I just changed my dash bulbs to LED and am having charging problems. I did not change my idicator bulbs, only the illumination bulbs.
__________________
1987 911 Carrera Coupe
1987 Buick Grand National
1971 Plymouth Roadrunner
Old 12-12-2018, 10:36 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #13 (permalink)
Almost Done
 
Join Date: Mar 2015
Location: ontario canada
Posts: 1,009
Garage
if you dont have the cprrect current flowing through the alt lamp. it can impact the current to the exciter and you dont get charging..ask me how I know after converting to LED!
Old 12-13-2018, 04:55 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #14 (permalink)
Registered User
 
Join Date: Oct 2005
Location: Capistrano Beach, Ca.
Posts: 7,148
Quote:
Originally Posted by Tori View Post
Hold the phone..... is this a thing? I just changed my dash bulbs to LED and am having charging problems. I did not change my idicator bulbs, only the illumination bulbs.
Yes, it is a "thing", but it only applies to your alternator warning lamp, not the dash illumination bulbs that are there to light the face of the gauges. You may, however, have mistakenly put a LED into the socket for the alternator lamp and that could have accounted for your problem. Or not.
__________________
L.J.
Recovering Porsche-holic
Gave up trying to stay clean
Stabilized on a Pelican I.V. drip
Old 12-13-2018, 07:29 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #15 (permalink)
Registered User
 
Tori's Avatar
 
Join Date: Jul 2016
Location: Pismo Beach, CA.
Posts: 653
Quote:
Originally Posted by ossiblue View Post
Yes, it is a "thing", but it only applies to your alternator warning lamp, not the dash illumination bulbs that are there to light the face of the gauges. You may, however, have mistakenly put a LED into the socket for the alternator lamp and that could have accounted for your problem. Or not.
Thanks for the confirmation, that is what i expected. I 99% sure i didn't get a bulb in the wrong spot as i had an extra left over (Carmagic kit comes with a spare bulb) and the illumination is even throughout the face.

I will still pull the gauge and investigate however.
__________________
1987 911 Carrera Coupe
1987 Buick Grand National
1971 Plymouth Roadrunner
Old 12-13-2018, 08:06 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #16 (permalink)
Tired Member
 
DaddyGlenn's Avatar
 
Join Date: Dec 2004
Location: Pittsburgh
Posts: 2,308
Garage
Sorry guys. Alternator arrived and was installed. Made the trip back from FL to PA with no further issues.

Had I been home when it happened, I would have tried replacing just the voltage regulator on the alternator first. But given I had to get back, replacing the whole unit was the quickest and easiest way to go.
__________________
Glenn
Daily Driver - '78 911SC RoW, Track - '85.1 944
Wife's - '00 740iL (Sport),
Support vehicle - '00 Suburban 2500 4x4
Son's - '85.1 944
Old 12-14-2018, 04:34 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #17 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 04:20 PM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.