Heater; cold air

[There is a valve on the heater hose where it goes into the firewall it works by vacuum . Also make sure
these hoses are hot when the engine is hot. If one is cold then the heater core has blockage. There is a door in the duct chamber also that open and closes.

[quote:ceca4f74fb="rrcarry"]1989 Coupe deville 66,000 actual mi 4.5 L No heat comes out even at 90° setting. Blows cold air only. A/C works great Prob for 6 mos. New radiator, thermostat, etc. last week; same prob persists.[/quote:ceca4f74fb]

there is no valve, but do ck the hoses for heat, if one is kinda cold the heater core may need flushing or replaced