[Vwdiesel] Apologies to Roger

[Smith, Michael]

If we remember that the amount of current gets less and less the further
down the ORIGINAL bussbar we go, then measurements are indeed more difficult
to ascertain.
Let's assume that the initial current in the bussbar is 48A and the pieces
of bussbar are all .001 Ohm (1 milliohm) & we are using 1 Ohm
GP's(glowplugs)
Across the first plug we'll see 48mV, 36mV,  24mV, then finally 12mV on the
last GP.  That doesn't leave a whole lot of "slop" for a variation
in readings does it?  What with motion, dirt, corrosion and natural
(un-natural?) movements in the meter it's a very relative thing and not a
conclusive result at all.
Also, each glowplug and each section of bussbar won't be EXACT either, so we
can't assume a definate "12mV drop" between weach one.  Resistance increases
with heat.....IE: the first leg of the bussbar with be slightly warmer than
each successive peice, thus its resistance will be more...hence more voltage
drop on each. Also there is more current in previous leg too.  It's not cut
and dried.  It's all RELATIVE.

I do like Hagars thinking on this (in a sense), in that it's quick, but is
it accurate?  The only way I could see this method working in REAL LIFE
is to already have 4 wires soldered or solidly crimped into place and run
back to the cabin(driver) and wired right into a meter with a 4 position
switch so you can quickly go "up the chain" as it were and see the
instantaneous voltage readings (in mV's) between GP's.  IE: 48mV,36mV,24mV
and 12mV.

To say there will always be a 12mV drop between them, and that it will
always be a specific voltage amount won't be correct IMHO.

It's never easy.

Mike in NB



> -----Original Message-----
> From:	vwdiesel-bounces at vwfans.com [SMTP:vwdiesel-bounces at vwfans.com] On
> Behalf Of Mark Shepherd
> Sent:	Wednesday, December 29, 2004 5:38 PM
> To:	vwdiesel at vwfans.com
> Subject:	[Vwdiesel] Apologies to Roger
> 
> I've reread your posting and its logic is converging with my
> own.
> 
> I think if we can take a good reading 'X' between #2 and #1
> then with all plugs good;  voltage will be double 'X'
> between #3 and #2 and triple 'X' between #4 and #3.
> I shant work out the 'dead GP' combinations as this is
> workoutable...
> Sorry Roger..
> 
> BUT here's another 'bone'
>   A week ago I had a glowplug die and then having replaced
> it 2 others died 2 days later :(
> It has been said on this forum that GP death is probably not
> linked save for general communal aging... If these plugs are
> rated at 11 Volts and whilst 4 are loading the battery and
> starter cranking is also dragging the battery down applied
> Volts are not too far above this. If a plug dies however
> then what effect does this have? 0.25 of a volt? Thats some
> 5 % extra power applied to the remaining plugs.. and if 2
> were to die how much brighter is the interior light? maybe
> 0.5 Volt? or 10% more power to the last plugs...?
> So maybe this is telling me that I should always change all
> plugs when one or more dies??
> Mark(The Miser)UK
> 
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