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Alternator/Battery Issues

I can do a lot of things myself but have to admit that electricals are my weakest suit. This is my RST, 78 chassis with 86 electricals and a 3.4 Turbo. Mods all over the place.
Interstate battery about 4 years old. Always gave me 12.5v with engine off and 14.41v with engine at idle. With voltmeter reads 12.9 volts at battery with engine ON and OFF for the past week. Today the voltage went down to 11.3 and then the engine died. Checked tightness of battery leads and connection to alternator at engine. Nothing more done until I have a plan.
Remember, electricals are not my strongest suit. Im really dumfounded as to why the reading was 12.0v with engine ON and OFF. I would have thought that the alternator would give me some uplift.
So, need help with a plan of attack. Thoughts?
Thanks in advance.
Johan
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Old 10-05-2017, 01:07 PM
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sounds to me like your alternator is not charging your battery. Many local auto parts stores will perform a free diagnostic on your car that could confirm this -- autozone in the states advertises this service . . . might be a good first step if the car still drives
Old 10-05-2017, 01:14 PM
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Quote:
Originally Posted by darrin View Post
sounds to me like your alternator is not charging your battery.
Agree.

Local parts stores sell alternators for the 911. They are not that exotic. Not being flippant. I put a run of the mill one in nine years ago. Doing fine.

Pelican has splendid ones and I believe you can upgrade to higher output units as well.
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Old 10-05-2017, 02:01 PM
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Quote:
Originally Posted by darrin View Post
sounds to me like your alternator is not charging your battery. Many local auto parts stores will perform a free diagnostic on your car that could confirm this -- autozone in the states advertises this service . . . might be a good first step if the car still drives
You are probably right. However, I'm unfortunately in cottage country 150 miles from Toronto so I would prefer to somehow test the alternator in the garage. Is there a DIY way through the multi pin connection coming out of the motor?

Johan
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Living well is life's best revenge- George Herbert (1593-1633)
2006 C2S, A4 Quattro, Evolution of a Carrera RST.
Old 10-05-2017, 03:33 PM
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Originally Posted by Bob Kontak View Post
Agree.

Local parts stores sell alternators for the 911. They are not that exotic. Not being flippant. I put a run of the mill one in nine years ago. Doing fine.

Pelican has splendid ones and I believe you can upgrade to higher output units as well.
Thanks for the heads up on this. Always thought that they were exotic.
Johan
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Old 10-05-2017, 03:34 PM
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Update.
HAd forgotten that I had a Dempsey Manual. There is a note in the alternator section that “in some models...” the alternator does not work if the idiot light is burned out. Really? What a stupid setup if true.
So I checked the bulb which turned out to be fine. The lead from the ignition switch to the idiot light had power with the switch on. However, the lead from the alternator to the light gave 12v with the ignition switch on but engine not started. 12v on both side does not light up a bulb. So the culprit appeared to be the voltage regulator or alternator.
As the VR had only about 10k km and the alternator was 31 years old with ~450k km I decided to replace both. Success, 14.4v.
Cheers,
Johan
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Last edited by Uwon; 10-13-2017 at 06:16 PM..
Old 10-13-2017, 03:46 AM
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Good morning Johan 150 miles in which direction from Toronto?
Old 10-13-2017, 04:35 AM
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Good morning Johan 150 miles in which direction from Toronto?
North. PM me.
Johan
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Old 10-13-2017, 06:17 PM
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