My '89 Vanagon is experiencing an intermittant coolant gauge failure. During
a long drive, the reading gradually started to drop over the course of an
hour or more, until it showed no reading at all. Even then, the heater still
blew hot. (The outside temperature was 85 degrees, but the interior of the
van was much cooler with the A/C running, and when I turned on the heat it
sure felt very hot on my feet.)  The gauge continued to show no reading at
all during the rest of the drive (about 90 minutes) and again on the entire
drive home (about 4 hours). There was no noticable difference in engine
performance.  

Then, on the next drive, the gauge read perfectly fine again.

Intermittant problems are always the hardest to diagnose, but I'm further
confused by the gradual drop in the reading. If it was a bad connection, I'd
have thought that the reading would have dropped suddenly, not gradually
over time. If it was a faulty temp sender, I wouldn't have expected it to
suddenly work again. And if it was an accurate reading (due to a bad
thermostat), the heater should have blown cold.  

I've never had a temp gauge or sender go bad, so I don't know if perhaps
this scenario is more common than I realize and there is a simple
explanation. Anyone have a similar experience?

- Ron Salmon
  The Bus Depot, Inc.
  www.busdepot.com
  (215)  234-VWVW

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