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
Registered
 
kpfoten's Avatar
 
Join Date: Feb 2003
Location: Gladstone, MI
Posts: 271
Alternator Question -- My light glows

Hi,

When I turn my ignition key to "on" the red alt. light comes on. Fine.. However, when I start the car up, the light will stay on at idle. I checked the battery and it's charging at 13.67 volts. Seems normal?

I realize I should probably have the alt. tested, but I'd like to drive the car and am afraid that I might be stranded somewhere.

Thanks

__________________
Kris - '77 911S
Old 07-17-2003, 06:15 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Registered
 
pwd72s's Avatar
 
Join Date: Apr 2001
Location: Linn County, Oregon
Posts: 48,568
13.67 sounds adequate.
__________________
"Now, to put a water-cooled engine in the rear and to have a radiator in the front, that's not very intelligent."
-Ferry Porsche (PANO, Oct. '73) (I, Paul D. have loved this quote since 1973. It will remain as long as I post here.)
Old 07-17-2003, 06:32 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered
 
Join Date: May 2000
Location: Los Alamos, NM, USA
Posts: 6,044
Sounds about normal. If you rev the engine up enough for the light to go out does the light come back on once the engine drops back down to idle speed?
Old 07-17-2003, 07:07 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
one of gods prototypes
 
bell's Avatar
 
Join Date: Nov 2001
Location: Orlando florida
Posts: 9,741
Garage
Send a message via AIM to bell Send a message via Yahoo to bell
what's your idle rpm? and your v-belt isn't too loose is it?
__________________
Brought to you by Carl's Jr.
Old 07-17-2003, 08:41 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered
 
Lorenfb's Avatar
 
Join Date: May 2003
Location: Manhattan Beach, CA
Posts: 2,350
You should have a SEV Marchel 70A alt. Given that, a glowing
light may mean:

1. You have a voltage drop from the alt. to the front & battery.

2. You have a alt. diode which is bad.

Note: The voltage being 13.7 does not necessarily indicate
that the alt. is OK. The regulator will force the alt. to charge
to the set voltage even w/o all diodes.

Good Luck
Loren
'88 3.2
__________________
Have Fun
Loren
Systems Consulting
Automotive Electronics

'88 911 3.2
'04 GSXR1000
'01 Ducati 996
'03 BMW BCR - Gone
Old 07-17-2003, 10:31 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Moderator
 
304065's Avatar
 
Join Date: Dec 2001
Posts: 9,569
See Warren's post about putting a resistor in parallel with the warning light bulb: this will put more current through the D+/61 "Blue Wire" circuit and provide you more excitation of the field at low revs.

But I agree, you could have a bad diode.
__________________
'66 911 #304065 Irischgruen
‘96 993 Carrera 2 Polarsilber
'81 R65
Ex-'71 911 PCA C-Stock Club Racer #806 (Sold 5/15/13)
Ex-'88 Carrera (Sold 3/29/02)
Ex-'91 Carrera 2 Cabriolet (Sold 8/20/04)
Ex-'89 944 Turbo S (Sold 8/21/20)
Old 07-18-2003, 04:02 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Registered
 
kpfoten's Avatar
 
Join Date: Feb 2003
Location: Gladstone, MI
Posts: 271
Thanks for the info--I'll check it out.

One note (and I may sound crazy saying this) but it seems like the light is _brighter_ after I tightened up the belt. (It was a bit loose when I first bought the car, and the light was dimmer)

Then again, it could be the desert peyote.
__________________
Kris - '77 911S
Old 07-18-2003, 05:51 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Heck, I’m only 5 not 71!
 
targa80's Avatar
 
Join Date: May 2002
Location: Jensen Beach, FL
Posts: 1,938
Garage
A dim Alt light at idle which goes out once the rpm's are increased has several possible causes as mentioned earlier. The Marcal alternator in my car had that problem and I troubleshot the problem down to the exciter diodes. The exciter diodes are not the main power diodes in the alternator. They are used to provide feedback voltage to the voltage regulator. In my case the exciter diodes were damaged by heat over many years of use. I replaced them with a three common all purpose 1N4000 diodes. The 1N4000 can be purchased at any electronic/radio shack store. They would have to be soldered in place with the correct polarity where the old exciter diodes are located. This was a cheap fix for my problem and the low glowing light was gone.
__________________
Pat Henry
Targa80
1980SC Targa (Mocha Brown)
Old 07-18-2003, 06:52 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Moderator
 
304065's Avatar
 
Join Date: Dec 2001
Posts: 9,569
Pat, that's cool. Do you have any pictures of the replacement of the "trio" diodes?
__________________
'66 911 #304065 Irischgruen
‘96 993 Carrera 2 Polarsilber
'81 R65
Ex-'71 911 PCA C-Stock Club Racer #806 (Sold 5/15/13)
Ex-'88 Carrera (Sold 3/29/02)
Ex-'91 Carrera 2 Cabriolet (Sold 8/20/04)
Ex-'89 944 Turbo S (Sold 8/21/20)
Old 07-18-2003, 07:25 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Registered
 
Lorenfb's Avatar
 
Join Date: May 2003
Location: Manhattan Beach, CA
Posts: 2,350
Do it right. Rebuild the complete alt. and don't mickey mouse
it by soldering in diodes w/o a complete fix.

Loren
'88 3.2
__________________
Have Fun
Loren
Systems Consulting
Automotive Electronics

'88 911 3.2
'04 GSXR1000
'01 Ducati 996
'03 BMW BCR - Gone
Old 07-18-2003, 07:47 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
Senior Member
 
Jdub's Avatar
 
Join Date: Nov 2000
Location: Great NorthWest
Posts: 3,950
How are your ground straps? Clean them up. Also have the battery bench-tested.

I agree that a complete rebuild may be in order - it really is not that expensive.

John
__________________
'78 Targa in Minerva Blue
Old 07-18-2003, 08:10 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)
Registered
 
kpfoten's Avatar
 
Join Date: Feb 2003
Location: Gladstone, MI
Posts: 271
Thanks. Knowing me, I'd solder something wrong and blow the whole thing up.

What does a rebuilt alternator run these days? (ballpark)
__________________
Kris - '77 911S
Old 07-18-2003, 08:32 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #12 (permalink)
 
Senior Member
 
Jdub's Avatar
 
Join Date: Nov 2000
Location: Great NorthWest
Posts: 3,950
A rebuild cost me about $125.00. They put in a new VR and the brushes (of course) and turned down the commutator (sp?) ring on which the brushes ride, among other things. I went ahead and bought a new battery at the same time, and cleaned every darn ground and replaced every darn fuse with new ones.

Typically that ring only has so many "turn downs" before it is useless. Anyone familiar with Hunt/Lucas magnetos can understand this process.

John
__________________
'78 Targa in Minerva Blue
Old 07-18-2003, 08:54 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #13 (permalink)
Registered
 
Join Date: Sep 2002
Location: Southlake, TX
Posts: 76
Send a message via AIM to Nickalex86
I had the same problem. I tightened the belt and now it's fine. Hope this helps.
__________________
for sale:

'72 vette 454 4spd steel city grey
'77 911s "black cherry" candy paint
'77 911s targa yellow
'91 integra ls special gsr swap
Old 07-18-2003, 09:14 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #14 (permalink)
Registered
 
david914's Avatar
 
Join Date: Jun 2002
Location: Richmond, VA
Posts: 1,418
Having similar trouble on my '82. Ordered a new regulator from Pelican on Wednesday. Took the alternator out today and did a quick check of the diodes. It appears one or more of the negative diodes is shorted. I get 0 ohms in both directions on all three. It looks like I might need to get a rebuilt alternator since you can't find just the diodes and fix it yourself anywhere. I've looked on the Pelican parts list, and although it mentions rebuilt alternators, none are listed for mine. Anyone know if this is something our host carries? (I tried calling, but it's Saturday and no one is home.) Better yet, is there a source for alternator diodes? The alternator is in good shape except for the diode problem.
__________________
David Dryden
'86 911 Coupe
'05 BMW X5 4.4i
Old 07-19-2003, 07:50 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #15 (permalink)
Registered
 
MY83SC's Avatar
 
Join Date: Apr 2003
Location: Orange County, California
Posts: 337
Have you tried going to yor local electronics store? That's where you would find diodes. You will not find them at an auto supply store or even on Pelican Parts. Remove a diode and bring it with you. They should be able to find a match.
__________________
Mike
83 SC
Old 07-19-2003, 08:15 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #16 (permalink)
Registered
 
david914's Avatar
 
Join Date: Jun 2002
Location: Richmond, VA
Posts: 1,418
The diodes in question are the large, pressed in type. Not the small exciter diodes. I'm not sure that you could find those at a typical electronics store, let alone Radio Shack. I've tried calling some of the local rebuilders, but of course, no one's open today.
__________________
David Dryden
'86 911 Coupe
'05 BMW X5 4.4i
Old 07-19-2003, 08:43 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #17 (permalink)
Heck, I’m only 5 not 71!
 
targa80's Avatar
 
Join Date: May 2002
Location: Jensen Beach, FL
Posts: 1,938
Garage
John_Cramer:

Sorry I don't have a picture of the exciter diodes but I believe someone posted pictures of them in a previous post some time ago.

LorenFB:

MikeyMouse around? I don't mickey mouse around when it comes to my car. I did a quality fix on my alternator over ten years ago for about a $1.50 and a few hours of my own time doing something I enjoy. Fortunately I have the knowledge and skill to perform this kind of repair.

David914:

If you look in the phone book you will find alternator rebuilders who are willing to sell the power diiodes/brushes to someone who wants to rebuild the alternator themselves. You can also purchase new berrings from a berring supply house. All you need is the number stamped on the side of the berring so they can match it up.
__________________
Pat Henry
Targa80
1980SC Targa (Mocha Brown)

Last edited by targa80; 07-19-2003 at 09:23 PM..
Old 07-19-2003, 09:20 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #18 (permalink)
Registered
 
david914's Avatar
 
Join Date: Jun 2002
Location: Richmond, VA
Posts: 1,418
Targa80:

Thanks. The alternator in my car was a rebuilt purchased from Automotion about 6+ years ago and is in great shape except for the diode problem. I'm a little hesitant to spend $200+ for something that could be effectively repaired by me for a fraction of that. Especially when it took 3 tries with Automotion to get a rebuilt unit that worked! I personally don't think that doing your own repairs is "Mickey Mouse" either as long as you are thorough...
__________________
David Dryden
'86 911 Coupe
'05 BMW X5 4.4i
Old 07-20-2003, 06:01 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #19 (permalink)
Registered
 
Lorenfb's Avatar
 
Join Date: May 2003
Location: Manhattan Beach, CA
Posts: 2,350
How many tries did it take to get it right? It's lots of fun to
R/R the alternator unitl it works, isn't it?

Loren
'88 3.2

__________________
Have Fun
Loren
Systems Consulting
Automotive Electronics

'88 911 3.2
'04 GSXR1000
'01 Ducati 996
'03 BMW BCR - Gone
Old 07-20-2003, 08:12 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #20 (permalink)
Reply


 


All times are GMT -8. The time now is 09:32 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2025, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2025 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.