2015 jeep wrangler unlimited heater blows cold air ac works well.
Use another vehicle if you think you are going to need heat.
Probably one of the blend doors is not operating.
Either car is over heating or there is restricted coolant flow to heater core. You can ruin your car if you drive it without coolant or coolant flow. Check coolant level, water pump and thermostat. Make sure you don’t have air in system.