[Vwdiesel] Temp light blinking-engine cold !

[Mike & Coreen Smith]

OK....went out to see if my 86 Golf would start after initially being warmed
up, then parked for 5 hours.
OUtside temp -15*C........remarkable, but it started rather easily.  This
morning @ -25*C there was no
chance whatsoever.  Guess it must've still been a tad bit "warm"........?

Problem is....when I revved it up to past 1500rpm (guessing, I have no tach)
the temp light started
blinking and the guage gradually (10 seconds ot so) went over to
"hot".........

I restarted the car (a few times), and with the engine idling along @ maybe
700rpm, the ignition/charge light was on (I think this is normal) and the
temp light was NOT blinking.  Yet, a few seconds after that initial REV, (I
presume to give the field windings in the alternator a self-charge) the temp
light once again began blinking, and the guage went over hard to HOT.  I
just let the car run a couple times, 30 seconds each time, in case by some
weird quirk the guage was somehow telling me something.

That being said, there is one wire off broken on my alternator........a
small red one.......I think runs the shifter light.  (yet, it's been like
this since a week or so ago......temp guage always acted normal)

I also just changed out the heater core, so it MAY be down a bit on
fluid....yet I've test driven the car a few times, 5 kms at a time......but
to overtemp within just a few seconds? After being shut off for 5
hours........ Doesn't seem possible?!

Ideas?  Another wire broken off?  No antifreeze flow across a sensor maybe?
What's with the guage/light being "OK" before alternator emitting current.
What am I not seeing?

TIA,
Mike in NB

Mike, Coreen & Corey Smith
699 Rte 616 Keswick Ridge
NB
Canada
E6L 1T1