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83 911 SC Charging Issue

I need some guidance on trouble shooting the charging system

1. Battery is 1 year old Bosch.
2. Battery light never worked since I bought the car
3. Have driven it over four years and never had a dead battery
4. Two weeks ago after a short trip it would not start.
5. Called AAA, jumped it and checked the charging system and said it was 11.4 Volts.
6. Removed old alternator. Installed new battery idiot light, checked circuit by grounding blue wire at engine and the idiot light was on
7. Installed new alternator.
8. Battery reading 12.53.
9. Started car reading at battery with engine at 1500 RPM 12.14 and battery light is on.
10. Alarm system is disconnected since i bought the car.
11. There are two wires under dash that are not connected. Connecting them does nothing. There is a switch next to them it does nothing. There is a switch in the ash tray it too does nothing.

So, now I have a battery light, that validates system is not charging with a new alternator. Not sure how to proceed. The new alternator has the red cable on the positive side, the engine and brown wire on the negative side and the blue wire at the top on the negative side with the fiber washer.......

Thanks in advance.
Help is appreciated.
Roadster.

Last edited by roadster49; 12-05-2017 at 06:09 PM..
Old 12-05-2017, 06:04 PM
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Would you confirm that the ground strap from the alt to the engine, and from the engine to the body are both solid and the straps have a known low resistance (are not old and calcified).
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Old 12-05-2017, 07:49 PM
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Have you revved the engine past 1500 rpm? Sometimes my VR doesn’t pick up until I do. (More like 1200 to 1500 really)
If yes, revving last 2000 rpm does nothing, it could be a bad Voltage Regulator in the new alternator, bad diodes, an open wire or very poor grounds.
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Old 12-05-2017, 07:57 PM
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Did you use a 4 watt bulb when you replaced it?
If you used a 2 watt it won’t work. Not enough of a load.
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Old 12-05-2017, 08:00 PM
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Update 12-6-17:
Found loose wire by engine fuse panel. I believe it goes to the left side of the connector and ask for confirmation. That wire comes off the bottom fuse and appears to be overheated at the base. Not sure if that has anything to do with the alternator.
-

New bulb is 4.6W. Light stays on and charging remains at 12.14
Reved engine to 3000 light stayed on. Old alternator behave the same.

Engine ground to alternator is solid and replaced when engine rebuilt.

Ground to transmission is original braided strap. Tight to engine and body.

I hooked up the blue wire on the negative side of the alternator but am wandering if it should be on the positive side.

One thing I will check tomorrow is the battery shut off switch. Will take it off to see if any change.

Thanks for comments.

Roadster49

Last edited by roadster49; 12-06-2017 at 07:47 PM..
Old 12-06-2017, 06:50 PM
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Definitely check the shut off switch. Some are made with crap pot metal and have very little material where current actually flows.
Old 12-06-2017, 07:32 PM
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This is how I have wired the alternator but the light stays on.

I have removed the battery shut off switch and no change

My rebuilder feels the blue wire and the ground wires need to be switched.

Should they?

Thanks
Roadster
Old 12-07-2017, 08:11 PM
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this picture is from a prior post and the blue wire is on the grounded side. Please advise.

Last edited by roadster49; 12-08-2017 at 02:01 AM..
Old 12-08-2017, 01:59 AM
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Correct wire connections.........

Quote:
Originally Posted by roadster49 View Post


this picture is from a prior post and the blue wire is on the grounded side. Please advise.


Dennis,

I hate to disagree with you but I think you are mistaken by moving the connection of the “BLUE wire” to the positive plate. Have you confirmed and looked at your alternator connections?

Roadster49 picture shows the correct connections. This is exactly the same shown in the Technical Bulletin 1 as:
B+ = red wire
D- = brown wires (2X)
61 = blue wire

Note: (From Technical bulletin) If battery charge indicator does not go out after starting engine, the exciter current is too weak because of 2 watt lamp. In this case, supplied resistor, part number 911-641-981-00 (91 Ohms, 5 Watts) must be supplied parallel to the battery charge indicator lamp.

Tony
Old 12-08-2017, 03:42 AM
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Quote:
Originally Posted by boyt911sc View Post
Dennis,

I hate to disagree with you but I think you are mistaken by moving the connection of the “BLUE wire” to the positive plate. Have you confirmed and looked at your alternator connections?

Roadster49 picture shows the correct connections. This is exactly the same shown in the Technical Bulletin 1 as:
B+ = red wire
D- = brown wires (2X)
61 = blue wire

Note: (From Technical bulletin) If battery charge indicator does not go out after starting engine, the exciter current is too weak because of 2 watt lamp. In this case, supplied resistor, part number 911-641-981-00 (91 Ohms, 5 Watts) must be supplied parallel to the battery charge indicator lamp.

Tony
You are correct!
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Old 12-08-2017, 04:12 AM
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1. Check the alt wire at the starter.
2. The big red wire at alt always should be soldered.
3. Alt may not have been rebuilt and tested correctly.
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Old 12-08-2017, 04:21 AM
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Early birds.....

Quote:
Originally Posted by mysocal911 View Post
You are correct!
Dave,

It is 7:00 AM now in Philadelphia, PA and California is 2 hours behind (DST). Are you in the West Coast and up at 5 AM? Thanks for your comment.

Tony

Last edited by boyt911sc; 12-08-2017 at 04:29 AM..
Old 12-08-2017, 04:26 AM
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Both the original and the new alternator behave the same.

The rebuilder tested the original alternator said it was fine when it was excited but until then it does not generate power.

He too felt the blue wire should move to positive side. He said when the blue wire is on the stud on the negative side it is always grounded and the battery light will stay on. Which is the current situation.

Note I have a 4.6W bulb.

ground wire to engine is solid and tight, chassis braided wire is original but tight.

Battery at 12.4 and with engine running 11.4


I will continue to Check connections at starter and other places.

Thanks

Last edited by roadster49; 12-08-2017 at 06:50 AM..
Old 12-08-2017, 06:47 AM
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did you remove the body ground and CLEAN it, same with battery to body. clean them
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Old 12-08-2017, 07:15 AM
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Blue wire is D+. It has to be positive or it won’t balance the positive applied at the lamp and allow it to go out.

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Last edited by timmy2; 12-08-2017 at 08:47 AM..
Old 12-08-2017, 08:39 AM
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For the 82/83 without external VR. Colors are indicated.
Now, Finding the terminal designation on that alternator may be a different story....

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Last edited by timmy2; 12-08-2017 at 08:51 AM..
Old 12-08-2017, 08:45 AM
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I deleted my earlier posts giving wrong information so others don’t follow the wrong advice.


Yup, I was wrong for the non VR terminal markings.
You have it wired correctly.
As per my spare alternator I have on hand, 61 is bottom right.

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Last edited by timmy2; 12-08-2017 at 09:26 AM..
Old 12-08-2017, 08:57 AM
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tech bulletin





Tech bulletin and other notes regarding the alternator w/internal regulator wiring

regards,
al
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Old 12-08-2017, 09:06 AM
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Do remember that ground wires deteriorate without any visual clue. If you have an original braided strap at the engine to body you may very well have a bad ground. It is cheap insurance to replace this before you start chasing other issues. Also, it is very true that you must rev the car past a certain point to cause the grounding to "take" with an newly installed alternator. that is, to overcome inherent resistance.
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Old 12-08-2017, 09:09 AM
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If it is wired correctly as in the picture I still have a problem causing the battery lite to illuminate. I will go over all ground connections as suggested.

It remains a puzzle to me as the indicated 61 is a direct stud into the ground side of the alternator causing it to always ground the lamp.


Thanks.

Last edited by roadster49; 12-08-2017 at 09:44 AM..
Old 12-08-2017, 09:35 AM
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