Thanks for the replies. I am also thinking it has something to do with the headlights. Like I said before, I never have the problem until I am driving at 2 in the morning and the fact it was happening so fast. The guage would actually go from all the way at the top to the middle in less than 15 seconds and back up again. I can't see that engine heating up and cooling down so fast. I don't seem to have the problem any other time. Of course that never dawned on me until last night when I was driving home and I had just put in the new thermostat earlier yesterday.

As far as the mechanical guage, if I did end up buying one and installing it, where on the engine would the sending unit be placed? Also, I am assuming that the two green plugs next to the thermostat housing are the sending unit for a 22R, is this correct?