Voltage reg?

[urq]

The climate control head does not have the highest current capacity in the
ground lead.  As you turn on heavy loads in the circuit like the CC fan it
causes a voltage drop in the ground lead to the CC, and thus a reduced
measured voltage.  Similarly there will be a voltage drop in the +12 supply,
but from my measurements it will be less than the drop in the ground.  

It is best to get the measurement directly from the alternator or battery,
but you may want to look at the supply to the cigarette lighter socket ...
it may be isolated enough to allow a good reading from inside the cabin
without having to pull up the back seat.  I know when I added the charging
system monitor in the console of the urq I thought to take power from there,
but then it didn't shut off with the ignition, so I had to pick up +12
elsewhere.  The "charging system monitor" I used was the guts from a
charging system tester that plugged into the cigarette lighter ...

I read down the thread to your earliest post, and it sounds like you may
have something in the alternator going on too, but if it produces higher
voltage at low RPMs I'd be wondering about the commutator brushes ... 

Steve Buchholz

-----Original Message-----

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)