Voltage reg?

[Huw Powell]

I suspect your car is behaving "normally".  The tach fluctuation made 
you start watching the voltmeter.  I suspect that part of the issue may 
be that the voltmeter is down a long chain of junk and sees a "pulled 
down" voltage that does not necessarily reflect the actual charge state.

I recommend hook up a separate VOM to, say, your battery posts and 
observing what happens directly there.

No harm in pulling the reg to check the brushes as well, of course.

Cody Forbes wrote:
> And one more update for today. I'm still seeing high 13's on average,  
> but then I turned on the vent fan. With the fan on it went from 13.8  
> to 12.3v immediately. Lights and fan took it to 11.0. When I turned  
> the lights off but fan still on it read 11.4. Upon stopping and  
> turning the fan off it shot immediately up to 14.3.
> 
> So maybe the VR is marginal, but it seems like the fan may be on it's  
> last legs too. Odd that it doesn't squeek or anything.
> 
> -Cody (mobile)
> 
> On May 15, 2010, at 6:08 PM, Cody Forbes <cody at 5000tq.com> wrote:
> 
>> Update:
>> On the way home it got more interesting. With no loads it now  
>> charges at 13.8-14v steady at idle, and fluctuates 13.4-13.8v above  
>> idle. As we got closer to home I turned on a bunch of loads  
>> including lights. It dropped to 12.5v initially, but after a few  
>> seconds crept back to 13.3v. It still is fluctuating more that I  
>> like, but overall the thing just seems to be better than it has in  
>> many years. It's beyond me why it charges more at idle than it does  
>> above idle. I'll keep it under supervision and post if anything  
>> changes.
>>
>> I got a note or two about that it should always charge 13.5 or  
>> better. Yes, this is true for nearly every car out there, but it  
>> just doesn't work out like that on a 5000. Most 5000's charge at a  
>> very peak of 13.5 under ideal conditions  with voltages under heavy  
>> load being less. The only real fix is Avi Merons Ultranator or at  
>> least the VR he uses.
>>
>> -Cody (mobile)
>>
>> On May 15, 2010, at 5:35 PM, Cody Forbes <cody at 5000tq.com> wrote:
>>
>>> I haven't seen a failure mode quite like this before so I shal employ
>>> the collective wisdom. Seems like a voltage regulator failing, but
>>> could maybe be bigger.
>>>
>>> So I'm cruising down the road in my '87 5ktq taking the family to the
>>> mall. At one point I noticed the tach fluctuate a little. Not quite
>>> like the old bouncing tach syndrome, just a lazy ~300rpm occillation
>>> while the engine was definately steady. I pulled up the volt meter in
>>> the climate control head and noticed that we were down to 10.3v. I
>>> immediately turned off the A/C and the voltage came quickly up to
>>> about 12.5v. This car has never been a great charger for the 4 years
>>> I've known it and two that Ive owned it, usually 12.8-13.0 daytime  
>>> and
>>> low 12's at night with lights and everything going. Anyways, when I
>>> stopped at the next light the voltage very quickly rose to 14.0v with
>>> the engine at idle. As soon as I raised the revs to pull away it
>>> dropped back to 12.5v. We were more than halfway to our destination  
>>> so
>>> I decided to motor on. On the highway voltage fluctuated 12.3-12.9.
>>> Back off the highway I noticed the voltage fluctuating with the
>>> cooling fan as it should, but it was swinging from about 12.3 with  
>>> the
>>> fan on to near 13.8 when it turned off.
>>>
>>> -Cody (mobile)
>>> _______________________________________________
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-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/