Alternator Question

Sun Dec 9 18:23:16 PST 2007

Wow, my typos were so bad you may have trouble interpreting.

I would first check ground - it is simpler ( and a common trouble  
point).
For this to be a common problem across various accessories it has to  
be either in the common wiring or in the alternator/battery feed or  
return, not an individual accessory's ground.

Next, if that fails, I would check B+.

Good luck, these are always annoying to track down,

Grant
On Dec 9, 2007, at 9:15 PM, Grant Lenahan wrote:

> Sounds like a very high impedance system.  I'd check ground first, B=
> n ext (its more complicated).
>
> Grant
> On Dec 9, 2007, at 5:28 PM, Vittorio Bares wrote:
>
>> More diagnosis:
>>
>> Leaving it at idle for a while seems to bring the (system) voltage
>> back
>> to the point where the gauge shows 14v (volt meter never shows more
>> than
>> 14).
>>
>> Cooling fan, or headlights instantly bring the voltage down below  
>> 12v.
>> Smaller accessories such as dome lights, blower or dash lights don't
>> have much of an effect.
>>
>> Tried using booster cables to ground the radiator fan to the  
>> motor. No
>> change.
>>
>> Engine revs have no effect on voltage once the system gets above
>> 12.5v.
>> Took the car for a test run - went well enough for a while - voltage
>> dipped a little when fan came on - but not bad. Then I tried the
>> lights,
>> ok for a short spell, then the fan came on and basically killed the
>> system. Charging well below 10v, car started running badly (not as
>> much
>> power, lightly missing) - looks like I was running on battery only  
>> (?)
>> and the extra juice from the lights on and the fan on sucked too much
>> out of it.
>>
>> Made it back home - let it idle for a while, gradually the volt meter
>> made it back into the normal range, around 14v.
>>
>> Right now, it would appear that the lights and the fan are running an
>> unusually high load - what does that actually mean in practical
>> terms -
>> what am I looking for?
>>
>> TIA,
>>
>> Vittorio -
>>
>>
>> -----Original Message-----
>> From: Grant Lenahan [mailto:glenahan at vfemail.net]
>> Sent: Sunday, December 09, 2007 2:50 PM
>> To: Vittorio Bares
>> Cc: Mark R; Steve Sears; quattro at audifans.com
>> Subject: Re: Alternator Question
>>
>> I'm not sure where to start, and excuse me if you know all this,  
>> but a
>> few comments and questions come to mind:
>>
>> 1. You say it shows 12.5V running at idle.  It should be 14+V. This
>> suggests the voltage is too low, preventing the regulator from
>> working.
>>
>> 2. You also say it is dropping when revving the motor. Is this
>> correct?
>> Current - and thus ability to maintain voltage across any given  
>> load -
>> should rise with RPMs.  Yet it is falling. The only explanation I can
>> think of is that the load is rising - faster than the rpms.  So what
>> draws power more at high rpms?  Under normal operating conditions,
>> nothign I can think of.
>>
>> So this is a long-winded prep to "stop trying to fix the alternator
>> and
>> go find the unusually high load".
>>
>> Or, of course, find out if something is current limiting the
>> alternator,
>> which might look similar.
>>
>> 3. If the diagnostic display now reads 12v - regardless of actual
>> voltage - it suggests that something is amiss in he dash cluster.
>>
>> 4. Could these be related? Or might the dash cluster simply be
>> inaccurate when working from a B+ voltage that is out of range. I  
>> dont
>> know, but I've seen that in the past. Way int he past.
>>
>> Good luck in your quest.
>>
>> Grant
>> On Dec 9, 2007, at 2:25 PM, Vittorio Bares wrote:
>>
>>> Back at it - I've replaced the alternator w/a refurbished one - I  
>>> now
>>> have 2 fully working units (tested at AutoZone) :\.
>>>
>>> Went back an cleaned contacts behind the snub nose (alternator
>>> bracket).
>>> Cleaned contacts to adjustment bracket.
>>>
>>> Voltage is dropping when revving the motor.
>>>
>>> The diagnostic display for voltage on the climates control  
>>> remains at
>>> 12.0 (channel 11). This is regardless of what the needle on the  
>>> gauge
>>> is doing. It used to properly indicate the voltage.
>>>
>>> Needle shows just over 12v on idle. Verified w/volt meter.
>>>
>>> Voltage off of the alternator (+ post to engine ground) is about
>>> 12.5v
>>
>>> (seems low). I presume (it has a 14v regulator) it should read 14v
>>> from somewhere - anyone know where to measure that from?
>>>
>>> Anyone know how to check continuity of exciter wire (blue) from
>>> alternator? Bentley says to check current across wire to alternator
>>> exciter post - I set my multi-meter to DC 250ma and the needle shot
>>> over max (?) Bentley says it should be between 150-180ma - indicates
>>> if its low to replace climate control board - doesn't say  
>>> anything if
>>> its above ?
>>>
>>> Steve suggests in the attached thread to check voltage from the
>>> battery
>>> - since the battery is charged via ground (I believe), would one try
>>> to directly from one of the alternator mounting brackets to the
>>> negative post on the battery (a direct ground)?
>>>
>>> BTW - this is on a 1990 Audi 200 avant.
>>>
>>> Thanks!
>>>
>>> Vittorio -
>>>
>>>
>>> -----Original Message-----
>>> From: quattro-bounces at audifans.com [mailto:quattro-
>>> bounces at audifans.com] On Behalf Of Mark R
>>> Sent: Monday, September 24, 2007 1:36 PM
>>> To: Steve Sears
>>> Cc: quattro at audifans.com
>>> Subject: Re: Alternator Question
>>>
>>> Steve's got it right... often overlooked is the primary wiring.   
>>> Audi
>>> didn't use the greatest wiring when new, and now you'll often find
>>> corrosion under the sheath due to moisture wicking.  Remember, the
>>> alternator has to have the ability to get the current (amperage) out
>>> as well.
>>>
>>> Another quick and dirty test is to check voltage at the battery
>>> versus
>>
>>> the alternator post (if available when engine is running).  Set up
>>> the
>>
>>> wiring before starting the engine.  If you see a voltage change  
>>> (drop
>>> along the wiring), you'll need some attention there.
>>>
>>> Cheers!
>>> Mark Rosenkrantz
>>>
>>>
>>> On 9/24/07, Steve Sears <steve.sears at soil-mat.on.ca> wrote:
>>>>
>>>> Vittorio,
>>>> If the alternator is one of those 110 amp units, then the two bolt
>>>> pivot is correct.  If it is the 90 amp unit, then it should have a
>>>> long bolt and nut at the pivot.  If you were to hook a long jumper
>>>> cable directly between the snubber mount to the battery ground,
>>>> would
>>
>>>> you get a different reading?
>>>> (The engine ground to chassis across one of the engine mounts  
>>>> may be
>>> bad).
>>>> You might also check the condition of the battery cable splice.
>>>> Cheers!
>>>> Steve Sears
>>>> 1962 and '64 Auto Union DKW Junior deLuxes 1980 Audi 5000
>>>> 1987 Audi 5000 Turbo Quattro
>>>>
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