88 renix runs too cold

Ok this is driving me crazy, I changed the thermostat today trying to fix this issue. 1988 4.0 always runs cold. Upper hose is cold, lower and heater hoses will hurt to hold onto for too long. This thermostat I just installed is a mopar brand, jiggle valve at 12 oClock position. Filled radiator through upper hose, filled block through thermostat housing until full. Installed hosed and topped expansion tank. Turn on the heat and fired it up. This is how it shows on the gauge.

For some reason the dam thing just won't open.

Look at my thread a page back, I have a 2.5 but I had the same problem. Solved it by completely removing the mechanical fan. However I have a mechanical gauge so I know for fact it's not a sensor issue.

My heater core cooled temps down by 20 degrees on its own, that and the fan combined caused my thermostat to never open. I still don't get stable temps but I'm running warmer then before.

You can also try restricting the flow through the heater core by partially cutting off flow from the thermostat housing to let the thermostat heat up.

Or you have a junk thermostat. I got frustrated at not completely knowing so I bought a candy thermometer and tested my newest current one 50+ times with hot and cold water.

Gauge reading cold while the lower hose is hot can be an air bubble in the head. Unscrew the sender for a minute (cold) until coolant comes out, then screw it back in.