My heater was hardly heating at all. I replaced thermastat. A little more heat, on 1993 Mercury Grand Marquis

but not much. Blower works fine. one hose gets hot, other one cold.

Asked by for the 1993 Mercury Grand Marquis
maybe your heater core is clogged
1 more answer
CK FOR AIR IN SYSTEM ALSO CK HEATER CONTROL VALVE OPERATION