w116 300sd 79' temp going up
 

While driving uphill on my 79 300sd, I have been noticing the temp gage needle moving up. It has been hot lately here in Southern California.

Did not have this problem last year around the same time.

What could be causing the temp gauge needle to move to the line between 80 deg C and 120 deg C. I'm assuming that based on the temp gauge markings that the indicated line is the 100 deg C marking.

Please advise

When does this occur? When sitting at a stop or moving slowly? Or does it happen all the time?

Temp gauge needle moves up fast when going uphill. Needle seems to not cool down much when driving in street traffic.

The 212 switch wire is disconnected, could that be the culprit.
Is the 212 switch/wire what kicks on one of the fans?

probably time for a new radiator,thermo,and flush.

Note to the Moderator

Meant to start this thread in the Diesel forum