[V8] blue wire

[Steven Kramer]

thanks for all of your responses to this issue.

Saved me a couple of hours in the repair.

blue wire was the culprit and was not making full contact.  Now car is 
charging.

Don't want to beat a dead horse.  And as an Audi owner I know not to 
look for trouble. Can't afford it rigt now anyway.

God, I guess I'll tempt fate.

Would the loose blue wire cause the combination of the three indicator 
lights to go dim ( battery, brake and cat) ? Mechanic checked the volts 
coming off the head and said they were 14 volts.

Just a couple of other things.  I have discussed these and have gotten 
used to them in my car.   Don't know if this may be related.

1.  Fuel gauge and temp gauge sometimes go out - when out the aux fan 
will not go on.
2.  Air bag light on - haven't gotten around to this one
3.  ABS light is on - previous owner ripped out whatever makes the abs 
work
4.  Climate control channel 11 shows a flat 12.0 regardless of load.
5.  Interior courtesy lights do not turn off automatically
6.  Neutral light on dashboard is intermittent - all other lights and 
gauges work ( except for fuel/temp issue)
7.  driver's side window switch to front passenger window is 
intermittent ( contacts)

Other than that car works fine :-)

Steven Kramer

On Jan 18, 2005, at 6:59 PM, Buchholz, Steven wrote:

> ... here are a couple other side notes that enter into the
> troubleshooting ...
>
> 1 - Remember that you can get some additional charging system
> troubleshooting info via the climate control head ... see what voltage
> it is getting ... anything 12.6v or below when the engine is running 
> and
> the system is generally unloaded (CC Fan off, headlights off) indicates
> that you are running on the energy built up in the battery, anything
> over that amount indicates that the system is charging.
>
> 2 - I remember reading in ABS troubleshooting that one of the first
> things to check if the "ABS OFF" light in the dash comes on and stays 
> on
> is to check the blue wire to the alternator.  Conversely, if you are 
> not
> seeing the "ABS OFF" light on it would tend to indicate that the blue
> wire is functioning correctly.
>
> Steve B
> San Jose, CA (USA)
>
>>
>> Let me add a little more to this:
>>
>> Does the alternator light come on when you first turn on the
>> key? (motor not
>> running)
>> Does it go out when the motor starts?
>> If so then the light bulb is good, and the alternator is
>> probably working.
>> If the above is true then measure the voltage at the battery
>> posts and at the
>> alternator posts. If the voltage at the battery posts is
>> below 13.8v but the
>> voltage at the alternator posts is at or above 13.8v then you
>> may have a bad
>> battery cable connection or bad cable.
>>
>> The reason the idiot light is off may have to do with where
>> the alternator
>> "senses" the voltage. As far as it knows, everything is fine,
>> but the voltage
>> drop from the alternator to the battery prevents the battery
>> from charging.
>>
>> Dave
>>
>>
>>
>> Quoting 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. :-(
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