Cadillac Repair: 93 CADILLAC DEVILLE Heater, windshield defroster, seal tabs

Question
I have a 93 cadillac sedan deville an the heat will not get real hot. Change the thermostat, but the heater still not getting hot at 90 degree temp setting. But while you are driving say on the highway gets a little warmer.Also how do you get heat to come out your top air vents.Only comes out on low temp setting say 70 degree. On high temp floor only.

Answer
Hi Louis,

      There are several problem areas here. Because Cadillac wants seal tabs installed with the coolant over the years they can accumulate inside the heater core and restricting the coolant flow. If one hose is hot and the other can be held that is a tip-off. At that point you could take the hoses off the core tubes and flush water both ways. Otherwise the core will need to be replaced.

     The Programmer motor gears might be starting to wear and that would cause the arm not to travel to the hot setting. To test for that remove the glovebox and behind it you will see the programmer with the 8" rod on top. Command the temp to 90 and when the motor stops unsnap the rod and see if it can move anymore. If it does or you can move the arm on the programmer by pushing/pulling then it needs to be replaced. If by moveing it all the way to hot with the rod unsnapped and the temp. doesn't get any hotter then there is a problem with the heater core, thermostat or engine operation.

   The last part about hot air from the vents that is programmed. Any temp. air can be sent to the windshield defroster. From 60 to aprox. 74 the air is from the dash vents and hotter than that only to the floor. Enough people complained about that issue that starting in 1994 I believe Cadillac had an override that allowed hotter air from the vents.

     Hope that helps answer your questions. Bill