My 84 did the same thing recently.  Mark Drillock was instrumental in
pointing out that the control relay (Relay #43) circuit on earlier
Wasserboxers is what causes that.  Starting in 86 (IIRC), they upgraded the
relay so that when the light continously blinks, the CORRECT temperature
appears on the gauge (provided of course the coolant isn't dumping out).  I
replaced the relay with the newer one and cleaned the sensor probes and
everything's working just fine now.

The original control relay for the earlier models is VW # 251-919-376
The control relay for the later models (and replacement for earlier) is VW #
191-919-376 A

Of course, this and much more discussion (and solutions) on this subject is
in the archives.

Jim Thompson
oldvolkshome@earthlink.net
jim@karmannghia.com
http://www.oldvolkshome.com
***********************
----- Original Message -----
From: "Scott Norville" <kr2no@EARTHLINK.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, August 12, 2004 10:01 PM
Subject: Re: overheating weirdness - expansion tank temporarily going empty

> Part of this issue is a quirk of the earlier WBX wiring (mine is a '83.5
and
> did the same thing): when the "empty" sensor in the top of the expansion
> tank (the one in the rear left of the engine room) is out of contact with
> coolant it not only makes the light flash (and it should falsh when the
key
> is first turned, its the test circuit), it also pegs the temperature
needle,
> no matter what the temperature actually is.