On the 84 the low coolant system flashes the light and causes the gauge to read high. Pull the low coolant controller out of the relay socket. That should make the gauge work normally regardless of coolant level. When the light flashes without turning off the engine check the coolant level in the pressure tank, (left, with the pressure cap on it). The coolant may be getting forced out of the tank. 

Dennis
 

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of WILLIAM WITZ
Sent: Monday, April 20, 2015 7:25 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Temp gauge / false reading

Hi all, i have an 84 Westy and my Temp Gauge is giving me a false reading. The needle will rise to full hot after about 10 minutes yet it is not low on coolant. When checked with an IR Gun the temps all are normal. I am not puking coolant and the fan will come on after a good long heat soak,I am getting no air out of  the bleeder at the Radiator. The Voltage stabilizer at the instrument cluster is reading 10.8- which is over the 10.5 in my Bentley . The Fuel Gauge is reading normally .When these things fail is it usually the sending unit the the expansion tank? I cleaned the contacts both inside and out. No joy. I am going to try connecting a 100 ohm 1 watt resistor as per The samba and see if I can center the Gauge. Any advice would be appreciated.
Thanks, Bill Witz