Voltage drop reading on guage '83 Coupe

Ben Swann benswann at comcast.net
Fri Feb 6 09:40:31 EST 2004

Older wiring connections on peripherals, but newer fusebox.

I am making some changes, and running ground from batt. neg. around engine
head and to front frame.

Also, I am relaying the high beams taking current directly off battery -
ground to battery, positive off alternator main feed.

I may run a few more graounds as you suggest and am double checking inside
ground points.

----- Original Message ----- 
From: "Paul Cole" <pcole at mn.rr.com>
To: "Ben Swann" <benswann at comcast.net>
Sent: Thursday, February 05, 2004 9:48 PM
Subject: Re: Voltage drop reading on guage '83 Coupe

> On Thu, 05 Feb 2004 10:56:13 -0500, Ben Swann wrote:
> >Subject: Voltage drop reading on guage  Vehicle:  '83 Coupe possibly
> >
> >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.
> >
> Ben,
> YES- the older coupes are notorious for having GROUND PATH voltage drops.
> #1- culprit is the alt. frame to batt neg. connection/path.
> #2- the main batt neg to engine ground.
> >Battery reads 12V with engine off.  13.7V +/- .3V varying at idle.
> >
> Other indicators- ALT idiot light glowing dimly when high loads placed on
> electrical system.
> >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.
> >
> >I know this is probably not a significant problem, but is there any good
> >
> Check ALL dash/engine compartment ground leads.
> Measure the voltage drop from the neg batt terminal to the alt frame
> if it's > .2-.3 volts you need a new ground path.
> ( worse I've ever seen was 1.4 VOLTS )
> One way I've used ( yeah ok it's pretty extreme ) is to
> drill&tap the alt. frame for an 8mm bolt and use a 18mm(3/4" or so)
> GROUND braid to run from the alt frame to the engine block and then to
> the batt neg terminal.
> Check all the engine bay grounds and all ground straps ( 3 or 4) from the
> to the engine block especially the main batt neg to engine block one
> at the back of the block.
> Check all the driver compartment grounds and the leads up to the dash.
> Check the voltage regulator on the instrument cluster too. That can give
> really wild instrument readings.
> Take a close look at the Bently wiring drawings for the car and notice
> WHAT voltage the dash meter is measuring and what GROUND ref.
> it's using.
> There is 30-90 AMPS running around this car and the electrons TRY to get
> back to the batt/alt grounds but sometimes take a rather circuitous route
> doing it. ANY voltage drop in the ground path can cause trouble.
> ( you should see what happens when the left rear light multi-connector
> fails and ungrounds the Left rear light assembly. bizarre is a mild
> of the resulting circuit faults. BTDT )
> The electricals in the older cars SUCK. The A/C wiring and lights are one
> (horrible) example of piss poor design. The connectors are NOT
> weather tight and the wire gauge is too small and what MORON thought
> running 10-15 AMPS of headlight current through the column switches
> was a GOOD idea.?
> Does your car have the old style VW fuse box or the newer Audi design?
> At least the newer one doesn't melt-down like the old one ( BTDTx2)
> >Ben
> >_______________________________________________
> >quattro mailing list
> >quattro at audifans.com
> >http://www.audifans.com/mailman/listinfo/quattro
> //************************
> Paul R. Cole:
> '91 Quattro Coupe - (spare)Daily Driver @ 262k mi.
> '91 200 TQ 20v- New Daily driver @244k.
> '84 Coupe (358k SAR), '84 Coupe (SAR) , 85 Coupe parts car
> '89 200TQ (WIP- SAR engine  & things) New track toy
> '80 924Turbo ( built to Carrera GTR specs)
> Bloomington,MN
> pcole at mn.rr.com #  Powered by OS/2 Warp 4
> //---------------------------------------

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