I JUST GOT MY 1972 ELDORADO WITH 38K MILES. HEATER FAN BLOW GREAT BUT NO HOT AIR. IS IT LIKELY I NEED A NEW HEATER CORE OR COULD IT BE AS SIMPLE AS REPLACING THE THERMOSTAT

try flushing the heater core with high pressure water from a garden hose. could also be a blend door issue.

First check the coolant level and make sure it is full. next go to the heater hoses at the firewall, make sure engine has warmed up, put your hand on each one of the heater hoses make sure they are both hot to the touch. If one is hot and the other cold then the heater core is plugged up and it might be possible to back flush it and fix the problem. If the hoses are both hot then you have flow thru the heater core and your problem would be under the dash and be related to a vacume leak or a broken actuator cable, or broken blend door. The engine temp should be about 195-210 degrees, air blowing thru the heater core and coming out of the vents should be about 135-160 degrees to maintain maximun temperature in the vehicle. If the engine temp does'nt reach the previously mentioned temp then replace the thermostat.