Jeep not heating

My jeep just recently stopped heating the cabin. I’m not sure where to start looking, but I replaced the coolant release valve on the engine block. The water pump was replaced by my mechanic there after. The engine is warm and indicated by the temp gage, but the blower is only blowing cold or luke warm air.

Where should I look for the problem?

Check the hoses to the heater core and make sure they are both hot. This would indicate the coolant is flowing through the core and the trouble is with the air box door.

Check the hoses going to and from the heater core. Are they hot when the engine is warmed up? If not, coolant is not flowing through the core.

If the hoses are hot the core is hot, and the problem is the blend door, in the HVAC system under the dashboard. The blend door directs airflow through the heater core for heat, or the AC evaporator for cold, or a combination of both, depending on the desired temperature.

If the blend door isn’t directing airflow through the heater core you won’t get any heat, or very little heat.

Didn’t your mechanic check to see if the heater core was hot?

Took the jeep out for a spin to heat things up…where is what i felt when i returned.

The tubes from the thermostat housing are 1 warm and other cool. The tubes go towards the firewall and have some sort of plastic coupling or something near the wall with a metal item attached (I have no idea what the plastic parts and metal object are…cannot find it in Haynes manual). The tubes are markedly cooler on the other side of this object. The tube that was warm (assumed to be the in-tube) was cooler on the other side…but still warmer than the “out-tube.”

Make sure the blend door(s) are working.

I crawled under the dash and found that the cable from the control panel to what is probably the blend door had broken off the plastic connector. I used some simply ingenuity to fix the problem and it functions fine. Thanks for the help!!