At 04:56 PM 7/22/2008, Scott Daniel  - Turbovans wrote:
>gas guage seems normal so far.

Suggesting it's probably not the voltage regulator.

>re "intermittent ground in the sender wiring, '
>It's a 1.9 wbxr, 1984..........single contact guage temp sender.
>Ground for the sender is  the sender  screwed into the engine.

Yes, I mean the sender wiring shorting to ground between the sender
and the gauge.  A full short would very rapidly peg the gauge and
likely damage it eventually, but a partial short would give a high
reading.  It could be in the sender I suppose, but I'd expect the
sender to fail open, not short.

>But I havn't even started investigating grounds, which are an
>obvious place to start looking.
>those push-on spade ground connectors above the fuse box, they just
>can't work after 20+ years in my opinion.

If they had used the correct brass terminals instead of steel they'd
probably be fine.  But of course at some point you have to make
contact with the steel body...

The flasher circuit needs a ground at the gauge, but the gauge itself
is only grounded through the sender.

>I removed the level control unit from an 86......and turned on the
>key - LED still flashes as normal.
>the LED function is totally in the guage I would think.
>and it can be triggered, or course, by an outside input, like the
>level sensor system.

That's correct.  The flasher has a three-second self-test at
power-on, and is supposed to trigger any time the gauge receives a
signal that would indicate overheat.  Once triggered it runs for
three seconds regardless.  The level controller simply simulates an
overheat condition (i.e. low resistance to ground) when it detects low coolant.

If you get no flash at power-on, the *strong* presumption is the
flasher circuit in the gauge is toast, or the gauge ground is
bad.  Again, this should not affect the actual gauge operation, only
the flasher.

>the key......and the guage needle seemed to have a mind of it's
>own.  I didn't ohm-check the sender for the guage
>yet.............should do that, but can't say I've ever especially
>seen a bad one for intermittlant erratic temp needle deflections.

A high gauge reading, assuming the +10v from the regulator is
correct, is absolutely guaranteed to be a problem of too little
resistance to ground somewhere, passing too much current through the
gauge.  I would *expect* that an internal short in the gauge would
make it read low rather than high, put perhaps not -- the gauge reads
power, and P=I^2xR.  I'd need some real resistances to figure it for
sure.  But to be safe, put in a different gauge before doing anything else.

--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage," '85 GL "Poor Relation"