At 02:32 AM 2/17/2013, Bill MacLachlan wrote:
>What's the most likely culprit ?

Which tank are you talking about, and define "enough"?  The one that
matters is the pressure tank that you have to lift the lid to see,
and strictly speaking any air in it at all is not normal, as it
should get purged out to the overflow tank and replaced during normal
operation.  However the low-coolant warning won't trigger until the
level is a couple inches down.

Assuming that's not the issue, pull the coolant level controller
(painted number 43 or 42).  If the blinking stays, the problem is
inside the gauge (search the archives, I and others have written
voluminously about how to deal with that).  If it goes, then usually
it's poor contact at the sender plug or dirty pins on the sender.

While you're near the pressure tank, examine it for stress cracking
at the belt line and in the sender socket and nearby areas.  The tank
is likely due to be replaced.  See
https://picasaweb.google.com/117189706757545167023/Vanagon1989PressureBottleStressCracking#5576291396462224082
for a belt line crack.

Yours,
David