I have a 90 Coupe Deville I tried everything I can think of to get heat to come from the vents. I've changed the temp guage from 60 degrees to 90 degrees andI can hear theair mix valve change direction of the air butall i get is cool air coming from the vents. I've checked the radiator level it was full, heater core hoses for leaks found none, replaced the thermostat, still no heat but I do need to recharge the R-12 for the A/C to work.Does the ac affect the operation of the heater or Is there anything else I need to check?






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Hey there Adixon........ Heater and air conditioner issues are not a bunch of fun simply because it involves getting into the dash area. Not always but usually. First check that your heater water valve is letting the hot water get to the heater core. This will be most likely a vacuum hose from the water valve vacuum motor. Next make sure the mix door is letting air from the blower motor pass through the heater core area. If either of the mode doors is not functioning properly you should still get heat just not out the proper outlet. Mix door issue could be mixture door control, or stuck mix door, like rusty hinge etc. Could also be an issue with the ambient sensor. The air mix door is usually accessed through the glove box area, pull glove box liner and you will have to pull off a black panel to get at the mix chamber. Good luck with that.

 

I took the Glovebox out and verified that the air mixvalve operated correctly. it did the rod moved and the airchanged from the upper vents to the floorvents when i change the temperture to a higher number. I opened the hood and felt the both hoses going into the heater coreand they were hot, i felt the box covering the heater core it was not hot but just warm. What is the Heater water valve?Is that the same as the thermostat? if it'snot then where is it located?

 

Hot water valve not the same as thermostat. If you have one, it will be on right center of firewall with heater hoses and a vacuum hose to it. Sounds like heater core is restricted.

 

SLOWROLL you were dead on I removed the heatercore and it was full of sand. bought a new one installed it and the heater works GREAT!!!!!!!!!!! THANKS

 

Another for the good old HEATER CORES ....

thanks for the update

one other point ..
often one can clear the heater core of sediment by disconnecting the hoses at the engine side of the firewall and flushing 1st through one hose then the other, using a garden hose and thus avoiding the task of removing the heater core.

also, if you had an abundance of sediment, keep your eyes open for a malfunction later .. of ..
the thermostat - except you got a new one,
the radiator.

you did change out the COOLANT .. right?
Please say you did ...

 

I changed all of the fluids when i first bought the car in August 07 do i need to change the radiator coolant again?