77' caddyman

my77' sedan deville does not blow any heat.i've had my thermastat,and heater core both checked.there both fine.it just blows cold air.please someone look out for me and help a caddy lover??

strmn94

did you replace the heater core or just looked at it. with mine, it turned out the it was bad.
another possibility is a vacuum controlled switch that controls the amount of hot water to the heater core.