No heat from heater?

Hold a cooking thermometer on the heater hose or in the radiator neck. Normal is around 190 degrees or a little higher. The hoses should be too hot to hold onto for very long. If the radiator hoses are hotter than the heater hoses, look for a water valve on the right fender that isn't switching. They are vacuum-controlled.

Here is a guide that will help

https://www.2carpros.com/articles/car-heater-not-working

There could also be an actuator that isn't moving the temperature door far enough.

caradiodoc

Check the thermostat and heater core-if okay could be a problem with the air mix/blend/mode doors-vacuum and actuators

Well there could be several things contributing to this, one is an air pocket in the system, be sure to bleed the system, the thermostat may be stuck, the engine coolant temp sensor may be bad, if there is a check engine light on, then have it scanned for free at autozone, it may verywell be related to your problem

Flushing heater core alway worked for me
Engine cool
lower the coolant level
Locate the two hoses running to the heater core
disconnect them at the engine side leaving hoses connected to heater core throw the firewall
use garden water hose and compressed air if possible
run the water and follow by air throw one side and out the other and vice versa
do that two to three times watching what leaving the heater core you are looking for the go flow and clear water to run throw
good luck
let me know