Voltage drop reading on guage '83 Coupe

[Ben Swann]

I tried to be clear, guess I wasn't.  All readings taken at the battery were
with a Digital Multimeter.  The readings from inside the car were all
referring to what was read on the factory guage,  guess I should not have
referred to it as a voltmeter.

Basically there is a difference in voltage between what I read at the
battery with DMM vs. what the guage installed in the guage cluster reports
from where it is wired.

I'm not trying to drive folks nuts, just trying to see if others who have
'82-83(perhaps later years) experience this apparent voltage drop.  Does
your "guage' needle flicker when accesories are turned on and off?

BTW, what should DMM read when engine running and no other accessories.  Is
13.7 sufficient to indicate charging satisfactorily, or should it be higher?

I basically am trying to determine if there is a problem with the car other
than that's just the way it operates as originally wired.

Ben
----- Original Message ----- 
From: "SJ" <syljay at optonline.net>
To: <quattro at audifans.com>
Cc: "Ben Swann" <benswann at comcast.net>
Sent: Thursday, February 05, 2004 12:40 PM
Subject: Re: Voltage drop reading on guage '83 Coupe


>
> > From: "Ben Swann" <benswann at comcast.net>
> >
> > Is it normal for the voltage reading on guage to read about 1-2V lower
> than battery voltage when accessories are turned on, in particular the
> climate control fan?    This car registers significantly lower on the
> voltmeter than at the battery.
> **** Define guage and voltmeter.
> Call your handheld voltmeter a  "DMM".
> Call the car instrument cluster voltage guage a "gauge".
>
> > Battery reads 12V with engine off.  13.7V +/- .3V varying at idle.
> **** Are you reading the DMM at the battery?
>
> > Voltmeter reads: about 11.5 with engine off.  Engine on, no accessories
> around 12.3.  When flasher operated, there is a noticable flicker in the
> guage needle.  As other accessories are turned on, the flicker becomes
more
> pronounced.  With lights on, guage reads around 11.5 and when fresh air
fan
> is on full, down around 10.5.
> **** Are you talking about the "guage"? The instrument cluster voltage
> guage?

YES - I'll call it a guage from now on.

If you are, keep in mind that this "guage" is not a precision
> instrument. Use your DMM for accuracy.
> You can calibrate your DMM low scale using a fresh 1.5 volt battery . .
.it
> should read 1.65 volts at room temperature.
> You can calibrate your DMM higher scale by measuring your car battery. It
> should read 12.6 to 12.7 volts when its fully charged.
>
> Now, there is a possibility that there is a voltage drop in the wiring
> between the battery and the instrument cluster. You can eliminate this
> possibility by using your DMM to check voltages in or around the
instrument
> cluster.
>
This is what I beleive is happening.  I am trying to verify if it is normal
for this particular car  - 1983 GT Coupe.  I think it would be because
similar wiring diagram (for '84 GT Coupe) show guage share the same circuit
with the fresh air fan, Radio, other guages.  Accoring to the diagram, there
is one positive lead in, and 1 ground wire out.

> I suspect that your problem is simply that the instrument cluster guage is
> not reading accurately.
>
>
> > I know this is probably not a significant problem, but is there any good
> workaround?
> **** If it was me, I would "recalibrate" the guage. One small white paint
> dot to indicate where the needle is at 13.7 volts, and one dot to indicate
> where the needle is at 12.6 volts. Make sure you apply the dots to show
> proper indication from the drivers eye's point of view.
>
> If you are really fussy, get another guage from the junkyard.
>
> By the way, if your car has the climate control system, you can read
system
> voltage using the climate control.

No this is analog, and pre-Delco controls
>
> <snip>
>
> >I am referring to the voltage drop as measured at the voltmeter in the
> console with respect to what I read with a VOM at the battery.
> **** Always use the same instrument(DMM) when comparing voltages.
Otherwise,
> you will drive yourself and the rest of us nuts.
>
>
> SJ
> 85 Dodge PU, D-250, 318, auto
> 85 Audi 4k - - sold but still on the road
> 88 Audi 5kq
> 90 Audi 100q
>