heater on 1995 Chrysler Town & Country

The heat is weak, and only works on low or medium, weakly. I've replaced the thermostat twice, so I dont know if it might be the heater core or what?

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1 answer
Is your engine temperature gauge reading normal? If the gauge is reading lower than normal, or it takes along time to get up to normal operating temperature, then the thermostat may be sticking open. Also, make sure the temperature blend door is operating normally.