Heater blows cold air

If the inlet temperature seems low at 180, the outlet seems ridiculously low at 108. You have an engine thermostat issue probably (should be in the 190's all day long...or more...with the engine warmed up). And you likely have a heater core issue, even though you say it's not plugged. Flow in and flow out should be very similar in termperature.

Plugged up oil cooler