First check is to look for 12v at the alternator connections with the engine
switched off.
If it is not there the thick brown from the alternator to the heavy-current
cable (sometimes on the solenoid, sometimes an insulated bolt under the RHS
toe-board) is bad.
If there is 12v start the engine and try again, make sure the alternator is
plugged in while you are doing this. On my cars the cap of the connector
can be removed exposing the terminals while it is plugged in. With the
engine running at a fast idle you should see about 14.5v on the thick
brown(s) and also the brown/yellow.
If you still see 12v then it is not charging, check that you have 12v on the
brown/yellow, I am asuming you will have. If you do, then the alternator is
bad, amazing as it may seem. If not, then check the continuity of the
brown/yellow back through the warning light to the white circuit.
If you see 14.5v at the alternator when the engine is running then check
again at the battery, you should see it there also, given the responses to
everything else above.
PaulH.
-----Original Message-----
From: Speedo79@aol.com <Speedo79@aol.com>
To: mgs@autox.team.net <mgs@autox.team.net>
Date: 24 October 1999 04:48
Subject: Charging Problems-Bad Harness?
>Dear Listers,
>
>The ignition light for my '77 MGB started coming on last week. It would
>flicker whenever the engine got above 3500 rpms, then it started coming on
at
>lower rpms as well. I checked the voltage across the poles of the battery
>with the car on and off, and found no difference. I pulled the year old
>rebuilt alternator, and had them check it at Kragen-no juice...NONE!
>I bought a new alternator from them (with lifetime warrenty-I made sure!)
and
>installed it last Monday...Yesterday the alternator stopped charging, and I
>got stranded at school with a dead battery. After the tow home, I pulled
the
>alternator and had it tested again-charging fine, but he offered to replace
>it anyways. I brought the new alternator home, charged the battery over
>night, and still no difference in voltage at the battery.
>Where should I start looking? Should I start pealing back the blue wrap
from
>the wiring and save up for a new harness? Any recomendations are welcome!
>
>Steve Sanchez
>PS. Where should I start looking for a new harness? Moss is prohibitively
>expensive.
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