Of the two coolant temp sensors one is for the gauge and the other is for
both the ECU and idle speed controller. The gauge sensor has absolutely no
effect on engine operation. Both rarely if ever actually go bad. What does
fail is the contacts on the connector plug and the wiring or ground
connection for the temp sensor circuit. The wire to the sensor can also go
bad. These 20+ year old wires can get a lot of resistance and cause sensor
readings to go way off. The temp sensor actually work by completing the
circuit form the ECU to the chassis. Since both the ECU and idle controller
use the same sensor any extreme resistance in this path throws both off. The
high resistance tells the ECU it is like -40 and causes the engine to go
rich or even flooding making starting difficult or impossible. Especially
during warm weather or a slightly warmed engine.

The temp 2 sensor connectors is the same as the fuel injectors. Auto stores
have a generic pigtail replacement that helps to replace the bad cored wire
close to the end. I like to use the butt connectors with the built in shrink
tube.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
TJ Hemrick
Sent: Tuesday, November 23, 2010 7:12 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Temp sensors

Hey gang,
  I searched the archives but as you imagine, the title of my post resulted
in a plethora of hits most completely unrelated.  I've had my 87 Vanagon GL
(2wd) parked for a few months now.  1st; it's parked because it will no
longer start and ran like, well, I won't cuss here.  On top of that, when it
did run, it stranded me a few times.  2nd; I haven't tried to fix it
becuause I replaced every fuel line, removed and cleaned the gas tank,
swapped out the injectors, distributor, AFM, ECU, etc..... and I'm freakin'
tired of trying so I let it sit and rust in disgust over the whole thing as
it will NOT start.  So, after I hit the archives, I'm fairly certain, one if
not both of my temp sensors may be the culprit.  Can anyone confirm with at
least some certainty that one or both temp sensors, if bad, will result in
horribly long start times (in excess of one minute of engine rotation), poor
off idle hesitation, stuttering, and general overall really poor running?
Trust me, I want to take all my VW stuff and just burn it all to the ground
and yes, that includes the syncro....Yeah, I'm still PO'd.  If I didn't have
to fix it, I'd go kick every body panel on that thing with my steel toe work
boots...

Thanks,

TJ