Ive got an express van with the 5.7 v8

I am in canada so my temp gauge is in celcius, it was pretty consistently showing between 70-80c which is 158-176f.

I thought for sure it was a faulty thermostat, however today I plugged in my OBD2 scanner with live data and driving around it reads 183F-194F which seems normal, contrary to the dash gauge

Im not sure weather Ive got a heater core blockage or something else but it blows cold air on any setting.. any ideas?

*UPDATE*

I exposed the heater core and used my temp gun on it.. seems the top right corner reaches the same temp my ECT did after warm up ~188f. while the opposite corner of the heater core was 155... really the whole lower half was low between 155-170. That dosent seem significant enough to have no heat ... i guess Ill replace the core... any opinions ?