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What causes the heater to blow cold air?

Tiny
DAN2002
  • MEMBER
  • 2001 KIA OPTIMA
Have no heat. The heater blows cold, have changed the thermostat and still blows cold. The top heater coil hose is hot, the bottom one is cold. I believe there is a blockage. Can anyone help me?
Saturday, January 7th, 2012 AT 10:35 PM

4 Replies

Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
Sounds like the heater core is blocked i would start by seeing if its clogged. If one is hot and the other cold something is stopping it from circulating. The manual doesnt show a heater control valve, so that leaves a clogged heater core or weak water flow from the pump. If the engine isnt running hot, then the heater core must have some kind of restriction or an air pocket in it.

See the guides below, they will help figure this out

https://www.2carpros.com/articles/car-heater-not-working

https://www.2carpros.com/articles/coolant-flush-and-refill-all-cars
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Saturday, January 7th, 2012 AT 10:47 PM
Tiny
BUCK121678
  • MEMBER
  • 2 POSTS
  • 2005 KIA OPTIMA
Heater problem
2005 Kia Optima Two Wheel Drive Automatic

air blows but no heat and when it gets up to temp it starts to over heat except when driving at higer speeds. I replaced the thermastat last summer
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Thursday, March 14th, 2019 AT 5:50 PM (Merged)
Tiny
DAVE H
  • MECHANIC
  • 13,383 POSTS
Check the water pump is working !
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Thursday, March 14th, 2019 AT 5:50 PM (Merged)
Tiny
BUCK121678
  • MEMBER
  • 2 POSTS
How do you know if water pump is working or not
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Thursday, March 14th, 2019 AT 5:50 PM (Merged)

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