[Vwdiesel] No glow ....

[Shawn Wright]

On 3 Oct 2005 at 23:19, Roger Brown <r.c.brown at ieee.org> wrote:

> Derek wrote:
> > Yup, that's the motor and I think I may have solved the problem.  I'll try to
> > confirm tomorrow.  I am sure its the glow plug temperature sender.  It makes
> > perfect sense.  With my switch hooked up ( a wire literally is wound on the
> > terminal that SHOULD be grounding to make the whole thing go like its supposed
> > to  ... ) it works fine.  So, I am simulating the ground that the relay should
> > be seeing from the temp sender, but isn't.  I guess the light on the dash is
> > also somehow connected to this sender ?  The great thing about all this, is
> > the fact that now that I know how it is all wired and supposed to work.  I can
> > hook up an intercept switch to prevent the GP's from turning on in the summer
> > when they are hardly needed ....
> 
> The temp. sender provides an input to the relay.  That input does two things. 
> One is it sets a timeout for the GP light on the dash whose on-time varies with
> coolant temperature; longer when cold, shorter (or not at all) when hot.  It
> also sets a second time out for the glow plugs themselves (via the heavy relay
> contacts in the GP module).  That on-time is longer than the GP light.  On some
> models, the sender is a variable resistance and that provides a wide range of
> on-times.  Other models use a temperature switch, on when colder the X degrees
> and off when warmer than X degrees.  There are a variety GP module circuit
> designs out there.  SOme are very robust and "do the right thing" given flakey
> temp sender inputs.  Other circuit designs are very finiky and and follow the
> GIGO rule (garbage in, garbage out).  I built a GP module tester a few years ago
> and tested a drawer full of good and "bad" modules.  Funny thing is given good
> inputs, all the modules (good and "bad") worked fine. However, when given bad
> inputs, the bad modules "failed" and the good modules worked.

Interesting... this sounds like the buzzing syndrome I've had on some relays. Shawn 
Wright
http://zuiko.sls.bc.ca/~swright
'85 Jetta D 
'88 Westy 1.6TD 5 speed
 (see progress at http://members.shaw.ca/vwdiesels)
'82 Diesel Westy