Checking O-360-A4A Vernatherm

I decided to check the vernatherm on my Archer's engine because it is
running on the high end of the green during summer flights. I had already
checked the sending unit and guage and found it to be OK. I then removed a
1" hex cap from the top left of the oil filter adapter on the accessory
case. It is a few inched below the elbow that attaches the crankcase vent
tube and so was not easy to get off. I had to grind away a bit of metal
from the outer diameter of a box end wrench to get it to fit between the hex
plug and the metal of the engine. The hex cap is hollow and inside I
found...nothing. I couldn't get a really good look because I had left my
mirror at home, but there was nothing obviously under the plug except a
threaded passage.

Is this where the vernatherm is supposed to be located? If it is and one is
not installed, just what happens to the oil temperature?

--
Regards,
Mike

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