Home  |  Forums  |  914 Info  |  Blogs
 
914World.com - The fastest growing online 914 community!
 
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG. This site is not affiliated with Porsche in any way.
Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners.
 

Welcome Guest ( Log In | Register )

 
Reply to this topicStart new topic
> Drop some knowledge: what external faults would prevent an alternator from charging?
Tdskip
post Feb 10 2021, 01:10 PM
Post #1


Advanced Member
****

Group: Members
Posts: 3,674
Joined: 1-December 17
From: soCal
Member No.: 21,666
Region Association: None



The 1975 is not recharging the battery, so I obviously have either a fault with the alternator or the wiring/charging circuit.

In the interest of being just slightly less of a dope than I currently am, what would cause the charging circuit to fail if it is not an internal alternator issue. In other words, if we assume that the alternator is healthy and there’s no issues with the brushes etc. internal to the alternator wear with the wiring I have gone sideways to result in it not charging?

This seems like a useful topic to get into the forum here, thanks in advance for the shared knowledge.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Jonathan Livesay
post Feb 10 2021, 01:16 PM
Post #2


Senior Member
***

Group: Members
Posts: 740
Joined: 13-March 10
From: La Canada CA
Member No.: 11,461
Region Association: None



QUOTE(Tdskip @ Feb 10 2021, 11:10 AM) *

The 1975 is not recharging the battery, so I obviously have either a fault with the alternator or the wiring/charging circuit.

In the interest of being just slightly less of a dope than I currently am, what would cause the charging circuit to fail if it is not an internal alternator issue. In other words, if we assume that the alternator is healthy and there’s no issues with the brushes etc. internal to the alternator wear with the wiring I have gone sideways to result in it not charging?

This seems like a useful topic to get into the forum here, thanks in advance for the shared knowledge.

Voltage regulator not regulating?
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
ClayPerrine
post Feb 10 2021, 01:29 PM
Post #3


Life's been good to me so far.....
***************

Group: Admin
Posts: 15,367
Joined: 11-September 03
From: Hurst, TX.
Member No.: 1,143
Region Association: NineFourteenerVille



Do a full field test on the alternator.

With the car running and the voltage regulator unplugged, hook a DVOM to the battery to measure battery voltage.

Send positive 12v to the field connection for the regulator.

You should see something around 14 to 16 volts at the battery, and hear the alternator whine as it loads up.


If that gets the alternator charging, you have a bad voltage regulator.

CAUTION: Don't leave it hooked up more than a few seconds to test. The alternator will overcharge the battery and boil out the acid. And that is not a good thing.



Clay
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
VaccaRabite
post Feb 10 2021, 02:45 PM
Post #4


En Garde!
**********

Group: Admin
Posts: 13,407
Joined: 15-December 03
From: Dallastown, PA
Member No.: 1,435
Region Association: MidAtlantic Region



Grounds. Check them. Clean them.
Even a small ground fault will cause you alternator not to charge your battery.

Read my thread from a few years back, which REALLY got into a weird issue that involved powder coat getting where it was not supposed to be, and causing juuuuust enough resistance to leave me stranded on longer drives.

http://www.914world.com/bbs2/index.php?sho...d++powder++coat

Also, I had an issue where while replacing the VR, I somehow pushed one of the terminals on the relay board through the potting. Alternator was not charging. Drove me NUTS. I found that one totally by accident while checking the chassis ground behind the battery and the terminal that had pushed through brushed my arm and startled the hell out of me.

Zach
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Mikey914
post Feb 10 2021, 03:06 PM
Post #5


The rubber man
**********

Group: Members
Posts: 12,625
Joined: 27-December 04
From: Hillsboro, OR
Member No.: 3,348
Region Association: None



Also, if your bulb for the alternator doesn't light up when you turn the key (or you have replaced with an LED) it will not get the small charge necessary to excite the field and allow it to charge.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
flyer86d
post Feb 10 2021, 04:03 PM
Post #6


Member
**

Group: Members
Posts: 417
Joined: 12-January 11
From: Corea, Maine
Member No.: 12,585
Region Association: North East States



QUOTE(Mikey914 @ Feb 10 2021, 04:06 PM) *

Also, if your bulb for the alternator doesn't light up when you turn the key (or you have replaced with an LED) it will not get the small charge necessary to excite the field and allow it to charge.


Yes! One of the old Mercedes that I had mysteriously stopped charging. It was a 1981 280CE grey market car. I called the shop that rebuilt all of my starters and alternators and their first question was if the alternator light came on when the ignition was first turned. Guess what? The bulb was dead. I replaced it and the alternator began charging.

Charlie
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Mikey914
post Feb 10 2021, 04:19 PM
Post #7


The rubber man
**********

Group: Members
Posts: 12,625
Joined: 27-December 04
From: Hillsboro, OR
Member No.: 3,348
Region Association: None



Hopefully this is it.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Tdskip
post Feb 10 2021, 05:35 PM
Post #8


Advanced Member
****

Group: Members
Posts: 3,674
Joined: 1-December 17
From: soCal
Member No.: 21,666
Region Association: None



Thanks for all of the responses - the bulb works (glows with key on and when running).

User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Jonathan Livesay
post Feb 10 2021, 07:59 PM
Post #9


Senior Member
***

Group: Members
Posts: 740
Joined: 13-March 10
From: La Canada CA
Member No.: 11,461
Region Association: None



QUOTE(Tdskip @ Feb 10 2021, 03:35 PM) *

Thanks for all of the responses - the bulb works (glows with key on and when running).

And it's not an LED bulb?
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
stickyfingers
post Feb 23 2021, 11:17 AM
Post #10


Member
**

Group: Members
Posts: 164
Joined: 19-February 21
From: Toronto
Member No.: 25,223
Region Association: Canada



QUOTE(Jonathan Livesay @ Feb 10 2021, 08:59 PM) *

QUOTE(Tdskip @ Feb 10 2021, 03:35 PM) *

Thanks for all of the responses - the bulb works (glows with key on and when running).

And it's not an LED bulb?


Not to hijack the thread but wanted to state that I'm having a similar issue. The alternator light is ON when in accessory mode or with the car started. I'm going to remove the voltage regulator (if anyone can give me a quick location of that it would be great - waiting for my 914 shop manual to arrive - total noob here). Hoping it maybe the voltage regulator.

The light wasn't on 2 weeks ago (it got shipped from BC over 3000+ Km to Ontario) as per the previous owner. Not sure if something came loose in transit. I've attached my charger that tests the alternator which says its fine. So I'm hoping its the voltage regulator that's bad.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
ndfrigi
post Feb 23 2021, 11:28 AM
Post #11


Advanced Member
****

Group: Members
Posts: 2,925
Joined: 21-August 11
From: Orange County
Member No.: 13,474
Region Association: Southern California



QUOTE(stickyfingers @ Feb 23 2021, 09:17 AM) *

QUOTE(Jonathan Livesay @ Feb 10 2021, 08:59 PM) *

QUOTE(Tdskip @ Feb 10 2021, 03:35 PM) *

Thanks for all of the responses - the bulb works (glows with key on and when running).

And it's not an LED bulb?


Not to hijack the thread but wanted to state that I'm having a similar issue. The alternator light is ON when in accessory mode or with the car started. I'm going to remove the voltage regulator (if anyone can give me a quick location of that it would be great - waiting for my 914 shop manual to arrive - total noob here). Hoping it maybe the voltage regulator.

The light wasn't on 2 weeks ago (it got shipped from BC over 3000+ Km to Ontario) as per the previous owner. Not sure if something came loose in transit. I've attached my charger that tests the alternator which says its fine. So I'm hoping its the voltage regulator that's bad.


engine bay driver side at the relay board


Attached Image
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Tdskip
post Feb 23 2021, 11:50 AM
Post #12


Advanced Member
****

Group: Members
Posts: 3,674
Joined: 1-December 17
From: soCal
Member No.: 21,666
Region Association: None



Highjack away if it helps, no worries.

My dash light is not an LED btw, so problem elsewhere.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
rick 918-S
post Feb 23 2021, 12:26 PM
Post #13


Hey nice rack! -Celette
***************

Group: Members
Posts: 20,354
Joined: 30-December 02
From: Now in Superior WI
Member No.: 43
Region Association: Northstar Region



Possibly a bad relay board. Clays test may rule this out too.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Mark Henry
post Feb 23 2021, 01:09 PM
Post #14


that's what I do!
***************

Group: Members
Posts: 20,065
Joined: 27-December 02
From: Port Hope, Ontario
Member No.: 26
Region Association: Canada



QUOTE(stickyfingers @ Feb 23 2021, 12:17 PM) *

QUOTE(Jonathan Livesay @ Feb 10 2021, 08:59 PM) *

QUOTE(Tdskip @ Feb 10 2021, 03:35 PM) *

Thanks for all of the responses - the bulb works (glows with key on and when running).

And it's not an LED bulb?


Not to hijack the thread but wanted to state that I'm having a similar issue. The alternator light is ON when in accessory mode or with the car started. I'm going to remove the voltage regulator (if anyone can give me a quick location of that it would be great - waiting for my 914 shop manual to arrive - total noob here). Hoping it maybe the voltage regulator.

The light wasn't on 2 weeks ago (it got shipped from BC over 3000+ Km to Ontario) as per the previous owner. Not sure if something came loose in transit. I've attached my charger that tests the alternator which says its fine. So I'm hoping its the voltage regulator that's bad.


I'm an hour east but if you need parts like the VR I do have some known good parts, just return or replace.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Spoke
post Feb 24 2021, 05:41 AM
Post #15


Jerry
*****

Group: Members
Posts: 6,964
Joined: 29-October 04
From: Allentown, PA
Member No.: 3,031
Region Association: None



You can do a rudimentary test on the alternator that Clay mentioned by removing the VR and shorting the D+ and DF pins on the VR connector on the relay board. Then start the car and measure the battery voltage. It should be around 16V for a good alternator.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
rgalla9146
post Feb 24 2021, 06:30 AM
Post #16


Advanced Member
****

Group: Members
Posts: 4,538
Joined: 23-November 05
From: Paramus NJ
Member No.: 5,176
Region Association: None




All great advise.
Do these basic checks as well.
Alternator belt tight ?
Battery terminals clean ? and tight ?
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
mate914
post Feb 24 2021, 06:38 AM
Post #17


Matt
***

Group: Members
Posts: 721
Joined: 27-February 09
From: Eagles mere, PA
Member No.: 10,102
Region Association: North East States



I was going to say grounds... also.
How about a loose belt?
Bad connections on battery?
As I have leaned its always the simple things that fail.
Matt
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Tdskip
post Mar 11 2021, 03:42 PM
Post #18


Advanced Member
****

Group: Members
Posts: 3,674
Joined: 1-December 17
From: soCal
Member No.: 21,666
Region Association: None



Hi folks – just wanted to close this out. Turns out I had a good alternator but a bad voltage regulator. Thank you for the help and knowledge, very much appreciated.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post

Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 



- Lo-Fi Version Time is now: 29th March 2024 - 12:36 AM