My 544 came with an aftermarket mechanical (non-electric) temp gauge. The sender screwed right into the stock location on the block. During the time I had that gauge, it never read more than 190 degrees - with a 195 thermostat in place. Fairly correct, considering!

I managed to track down a functioning original gauge and I replaced the aftermarekt gauge with that one. The 'stock' Volvo gauge sits at about 3/4 until I start to climb a grade or have to sit in traffic for more than a few minutes, and will peg out until I begin to get more airflow through the radiator.

I'd like to get either the cooling system to keep the engine at a cooler temp or get the gauge to read correctly.

Recently I obtained a complete 544 dash gauge panel, so I now have an extra temp gauge. I plan to put the sensor, along with my 'old' aftermarket gauge, into a pot of water on the stove and compare temps across the range. Then I'll adjust the stock gauge so it reads more-or-less correctly and install the new gauge when I go into the gauge panel to fix the trip odometer.