1977 Buick Riviera climate control not working...no heat

SOURCE: 2002 montana getting overheated

sounds like a stuck thermostat. but check if the system has a bleeder screw if it does burp it and that will help also.

SOURCE: 1998 Dodge Durango no heat when using heater.

BLEND DOOR STUCK OR BROKEN. NEEDS TO REMOVE DASH AND HEATER/EVAP CORE BOS TO REPAIR REPLACE.

SOURCE: 1993 ford taurus no heat

if only cold air comes out it would be the t-stat

SOURCE: How to replace heater core 1983 Buick Riviera

GO TO YOUR LOCAL PARTS STORE FOR A REPAIR MANUAL FOR YOUR AUTO.IF THEY DO NOT HAVE IT,GO TO HAYNES.COM.TO LOOK UP WHAT YOU NEED.

SOURCE: blowing cold air via the heater

Assuming that none of the Electrical/Electronic controls were disturbed when changing the Thermostat it seems to me that you have an "Air Lock" within the heater. One must purge all the air out of the cooling system as close to the highest point as possible after the system has been partially or fully drained. Most of the time one will find small BRASS Bleeder Valves located somewhere near the highest point. Open each one while the system is pressurized and let Air escape until some Coolant escapes. Sometimes it may be necessary to loosen a Heater Hose and bleed the air at that point. Remember that the system MUST BE PRESSURIZED to accomplish the Bleeding of Air. Many auto parts stores sell hand pumps with a pressure gauge for this purpose and leak testing. These pumps typically replace the Radiator Pressure Cap temporarily. The system does not have to be at normal operating temperature to bleed the air out. Once the Air has been bled you will have to refill the radiator to normal full and make sure that the Coolant Recovery Tank level is also brought up to recommended level. A quick check is to remove the Radiator Pressure Cap, Start the Engine, Rev the engine suddenly (A short Jab) and see if the coolant level falls rapidly in the radiator. If it does it is definitely an AIR LOCK situation.

Fastest Robe

Testimonial: "Thank you, I'll do the quick jab test to determine the air lock and proceed with bleeding"