Well the 1993 2.3l has the coolant temp sender at the back of the engine, drivers side, bad placement so it does show cooler than the actual temp at the top front of the engine where thermostat is
Seen here:
https://cimg4.ibsrv.net/gimg/www.ra..._d3c13ce3af4920cf917bb86d6913e996a27c731c.gif
In later years Ford moved it to the upper heater hose at engine end
But gauge should be steady, just not up at 1/2 like most Ranger V6's, maybe 1/3 on the 2.3l
And always use a 190-195deg T-stat
To refill without trapping air remove both heater hoses at the firewall
Refill thru radiator, when coolant starts to come out of hoses re-attach them
Also use garden hose on heater core to flush it out in BOTH directions
Also you should Reverse heater hoses at the firewall once a year, it will make core last longer
You don't lose coolant when you do this, well very very little
One other heads up about the heater core, its not expensive or hard to change on 1994 and earlier Rangers
And if it starts to clog up the temp gauge will go up and down for no reason, just random up and down
Thats because the heater core is the water pumps by-pass