[Vwdiesel] Glow Plug testing ---- ( the FAST FAST way. ).Explain moreplease

[Roger Brown]

Mark Shepherd wrote:
> 
> The voltage drop method needs some research as it dosent
> behave quite like Roger states...
> 
> Imagine feeding glowplugs as per normal fed along a bus bar
> from #4 through #3, #2, and finally #1.
> Measuring from #2 to #1 gives a voltage drop say XmV looking
> from between#3 and #2 would give a voltage drop of XmV as
> well even if we snapped off #2 as the bus bar has a
> nominally equal voltage drop along its length (ie) so many
> ohms per metre.
> So does the voltage drop increase from its 2  lots of 'X'mV
> which would show up with a measurement between #3 and #1
> with #2 open circuit or what?????

I suspect that yes, you'll see some drop due to the length (or resistance) and some due to the current.  The main problem is you
are looking at very small voltages (you need a really good meter to do so) and the connections to the sensing points are
critical.  So its all going to be relative measurements and the changes between points and it'll be darn hard to figure out the
observed voltage drops relate to exactly which plug is bad in all cases.

You may even see variations in current draw between the different plugs and the cross sectional area and length of the copper
bus bar probably varies a bit between segments.  Separate wires are the way to go.  Got to get some time to wire up my glow plug
monitoring circuit, it should give a visible indication of each working (and non-working) glow plug.  If it works as planned, it
should be an easy install, hardest part will be swapping the 4 bus bar connections for separate wires, then connect the
monitoring module to the fusible link and ground and it is ready to go.

--
   Roger