94 deville heat blows hot only 1/2 the time.
 

I changed the water pump, thermostat, and engine coolant. Yet the heat won't get hot like it use to. Sometimes it will get hot. Then u can drive it the next day and the heat won't get hot. Then sometimes the heat will get hot after like 30 minutes. i think it could be the heat from the engine warming the car after the 30 minutes though. HELP, HELP, HELP!!! THE AIR BLOWS THROUGH THE DEFROST AND THE FLOOR LIKE IT'S SUPPOSED TO. BUT IT WON'T GET HOT. I TOUCHED THE HEATER CORE HOSES UNDER THE HOOD. ONE DAY THEY BOTH TO HOT TO TOUCH THEN THE NEXT DAY ONE WAS KINDA HOT AND THE OTHER WAS KINDA COOL WITH THE HEAT ON 90 DEGRREES.

RE: 94 deville heat blows hot only 1/2 the time.
 

Hey Big: You could think about replacing the heater check valve which should be up near the firewall, you will see two heater hoses coming into it, it's not that big, maybe three inches long. I changed this and it helped. The next thing is the heater mixing door. To get at it you have to take the glove box liner out and it will be in behind that. You should see a black plastic cover over the opening. Pop the cover off and reach in and flex the door back and forth with you hand. It should move freely. Put some WD40 or other lubricant on the hinge point. The servo motor that actuates this door is not very big and it has trouble doing so because the hinge gets rusty from condensation in this area. Hope this help, and enjoy your ride.

RE: 94 deville heat blows hot only 1/2 the time.
 

i had a similar problem but then i didnt have heat at all and i found out that my heater core was pluged up because the previous owner had used some stop leak crap and it pluged up the htr core. yours could be some what pluged. try to flush the coolant system if you havent already. also you can try to flush just the htr core to see if it is pluged. good luck.