[V8] blue wire

[dsaad at icehouse.net]

I don't have my wiring diagrams handy - but I am 98.76% sure that this blue wire
is the "turn on" wire. If you have 12 volts on it with the key on then it is
probably working fine. I don't see the need to tear up the dash for this.
I don't want to second guess your mechanic but - well really I do want to second
guess him.
There is likely to be a fuse for the alternator. Has he checked for it?
Has he pulled the alternator and bench tested it?
$80 an hour is too much to pay someone to learn how alternators work.


Alternators 101:
(this applies to almost any modern alternator with an internal regulator)

The big heavy wire goes directly to the battery and is how the alternator
charges the battery and powers the cars electrical system. It is the "output" of
the alternator

The smaller wire (usually marked "Field") has two purposes:

First it supplies power (input) to the voltage regulator. When the key is in the
"on" position you should see battery voltage on this wire.

Second, it is the "voltage sense" wire. When the motor is running and the
alternator is working, the alternator will keep the voltage on this input below
around 13.8 volts. The regulator handles this job so if you have battery voltage
on the blue wire and the alternator is not charging then you have a bad
alternator.

If there is a third wire it is usually for the idiot light or guage.

There may also be a heavy ground wire.



Dave


Quoting Steve Kramer <skramer at mac.com>:

> Fellow V8er's,
>
>     Last told you about my v8 not holding charge.  Mechanic says battery
> light (alternator) does not go on. Can anyone lead me to the place where the
> blue wire goes from the alternator to the instument cluster?
>
> He has the whole cluster taken apart and this is when that $80 bucks an hour
> gets pretty scary.  Unfortunately, I cannot do this myself so I am at the
> mercy of a mechanic who has very limited experience with a V8. :-(
>
>
>
> Thanks,
>
> Steve Kramer
> 1990v8
>
>
>
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