1997 chyenne 350 heater/air problems

Ok first thing is my heater is not blowing as warm as it should. Im gettin 85-90 at the vent. The heater used to blow so hot (like 120)I didnt even have to turn it on, just turn the temp control on hot and it would warm up the entire cab. Now I cant even get warm in the cab. I recently did a coolant flush and have brand new coolant. Now here is the problem. The vent control (floor, front, defrost) switch doesnt seem to be workin correctly. Sometimes it seems like the air gets stuck and it doesnt come out the vents, and then if I hit a bump or rev up, Ill hear a thump like the flapper and then it starts blowing out the vent. But also Im not sure if the temp control switch is properly working. It does blow cold on cold and warm on hot, just not enough to satisfy me. The ac has never blown really cold for me either. Im wonderin if the flapper or temp blend door has something wrong. Just really frustrated. Heat used to work excellent and now works half ass. I checked the heater core and its fine. Both hoses are very hot. Did I do something wrong at the coolant flush?? Air bubble maybe? Or is it the actuator or temp blend door???? Thanks for the help.

well take the rad cap off and let in run to purge the air out. and replace the thermostat there cheap and easy to replace. then check it again if not a service manual will help you diagnose it you can even check one out at the library

What is the temp gauge reading? If it's reading low and/or fluctuating dramatically then you most likely have air in the system. Check the radiator every morning when cold and add coolant as needed. Keep the coolant reservoir full. It sometimes takes a while to purge all the air out.

The temp door actuator can be seen by removing the glove box. Small upside down house thing. Has index marks for full travel. Key needs to be on and rotate temp dial to watch travel.

Blend door actuator is at the left end of the plenum. Same house thing. Key needs to be on and the fan running to check travel.

Issues with both these door are usually caused by debris that has found its way into the plenum.

If you can observe the selector door movement as you cycle it, watch how it moves. If it moves slowly before stopping it is likely an obstruction in the duct. If it moves then stops abruptly, it might be internal to the stepper motor.

Case in point for the latter.... When I got the Vibe, the fresh/recirc mode door would not move at all. Without going into gross detail about what I found in the ducting from my mother-in-law's neglect, the foreign mass had caused the motor to partially break one of the internal gear teeth and lay it against an adjacent tooth. As soon as the motor gear hit this, it stopped. I fixed it by removing the broken gear, turning it 180° and reinstalling it. The door only travels ~90° so it never turns the gear enough to hit the bad spot. Problem solved and no money spent.

Hope it's this simple for you too. good luck!