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my 2000 jeep cherokee sport blows only cold air when i turn on the heat ! what could cause this ?  

there are several things...

low coolant level..

clogged heater core...

loose or leaking vacuum hose...

failed actuator..

stuck blend door...



1. Evaporator
2. Heater core
3. W/o AC
4. W/o AC
5. Ring
6. Blend air door
7. Recirculating
8. Blend air door actuator
9. Defrost
10. Panel & floor
11. Recirculating
12. W/o AC
13. Defroster, demister
14. Vent opening
15. Drain to dash, W/AC
16. Clip
17. Recirculating valve
18. Heater door


can you verify that when you move the various AC heater controls.. that you can control the air from the foot wells.. to the dash outlets.. to the defroster outlets...


if the thermostat is MISSING.. stuck open..  broken open... the coolant will circulate through the radiator .. not build up enough pressure behind a closed thermostat to flow the hot coolant through the heater core..

so you might want to see if the coolant is circulating too fast through the radiator...