<VV> Spyder Temp-Press light diagnosis

[Doug Mackintosh]

OK guys, I am looking for some ideas or experience-based explanations for a problem I have had.
The car is my daughter's 1964 Spyder. Have been driving it regularly with no problems. I recently drove it to Farmville (a little over 1 hour away). When I drove back home about 10 minutes from home the Temp-Press light came on and stayed on. 
There were no other symptoms. The temperature gage did not go into scary territory, there was no lifter clacking, loss of performance, problems idling at stops etc. The fan belt was still on. No noises. Oil level OK.
I continued driving home and switched it off (the light stayed on the whole time until I switched it off). 
I figured it most likely was either a pressure sensor failure or a shorted wire. Today (5 days later) I did some diagnostics by testing the light status after disconnecting the pressure sensor wire, then after grounding the pressure wire and then the temperature warning wire heading to the dash. Based on my testing everything was working as it should with the engine off. I then started the engine and the light went off as normal after it started. 
So at this point it seems to have "fixed" itself.
Ideas?
-- Doug Mackintosh Corsa member since 1996 Corsa/NC member since 1996, Virtual Vairs member Corvair owner 1969-1971 and 1996-on