Alternator Question

Mon Dec 10 12:41:32 PST 2007

Thanks for all the information.

It would appear that the current test and resistance test on the exciter
wire failed. I've been told that there is a zenith diode on a circuit
board somewhere and that the circuit board needs to be changed out.

The question is - where is said circuit board? Is it in the dash or in
the climate control box? Could this be exhibited as a gradual failure?

Thanks again! 

Vittorio -

-----Original Message-----
From: Grant Lenahan [mailto:glenahan at vfemail.net] 
Sent: Sunday, December 09, 2007 9:23 PM
To: Grant Lenahan
Cc: Vittorio Bares; quattro at audifans.com; Steve Sears; Mark R
Subject: Re: Alternator Question

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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