[T2] Engine Ground voltage drop under load, please help diagnose.

[accessys at smart.net]

I some years ago added a redundant ground path directly from the battery 
to the engine,  in my case a very heavy wire #O gauge from battery 
terminal to the bolt that holds the coil to the engine. but any solid 
engine point would probably work.

I did not remove the factory grounding path but rather added another.

Bob



On Sun, 11 Sep 2016, Christophe Guilbert wrote:

> Date: Sun, 11 Sep 2016 22:04:48 -0700
> From: Christophe Guilbert <cguilbert69 at gmail.com>
> To: type2 at type2.com
> Subject: [T2] Engine Ground voltage drop under load, please help diagnose.
> 
> Hi guys.
>
> I have a vanagon 1983 air-cool CA.
>
> I would really appreciate some help to diagnose my problem , even my
> mechanic does not understand it.
>
> Here is the story:
>
> My battery is new and read 12.6v . I have a new alternator which deliver 14V
>
> When the van idle I read 13.71V at the battery terminal. When I start
> lights and fan blower , I read 13.24V.
>
> I tried to check if I had any leak between the battery terminal and the
> alternator under load (lights and fan blower):
>
> For terminal + , I have none , well something like -0.1V
>
> For terminal - , not only I have -0.5V at the alternator level but also to
> any ground point of the engine,  which is way too much ! ( I have -0.1V
> only if I am not under load)
>
> In order to remind how the engine is grounded , here is the pathway , from
> battery to the body using a ground strap , than from body to transmission
> front  mounting using a ground strap, than from transmission front mounting
> to the transmission via metal contact and/or 3 bolts and stud. than from
> transmission to the whole engine.
>
> Trying to understand where my 0.5v drops come from , I checked if I had any
> voltage drop between the battery ground terminal and the ground strap
> terminal bolted to the transmission front mounting . I have none (-0.04v)
> .  So voltage drop must happened between the transmission front mounting
> and the transmission or the engine.  I plugged my voltmeter between  the
> ground strap terminal going to the transmission front mounting and the
> engine (any points) and I found -0.45V.
>
> When I plugged my voltmeter  between  the ground strap terminal going to
> the transmission front mounting bolt and one of the transmission bolt
> (after making it bare metal), I got -0.35V. So the main culprit seems to be
> the connection between the transmission front mounting and the transmission
> itself. I removed the transmission front mounting , clean bolts ,studs,
> washers, any point of contacts, I make them bare metal, used deoxit D5 and
> di-electric grease before putting every back. I retest the ground voltage
> between the battery and the engine and I got -0.4V (instead of -0.5V) under
> load.
>
>> From this point I don't know what to do and would appreciate any
> explanation and advices.
>
> I am thinking to reground the engine . If I quickly used a  jump start
> cable to reground the engine , I reduce my voltage drop from -0.4V to
> -0.2V. I guess I can do better with  a proper dedicated ground cable .
>
> I would rather avoid  that option thought because I would like to fully
> understand what's going on first.
>
> Any though.
>
> Thanks for any help.
>
> Chris
> _______________________________________________
> type2 mailing list
> type2 at type2.com
> https://www.type2.com/lists/type2/listinfo
>