Heater does not blow hot air. Blower does works only cold air comes out regardless of changing temp on cold to hot dial

check to make sure the blend door is changing from cold to hot. With the engine off and the key in the run position set the blower motor to the highest speed. Turn the temp dial to full cold and wait 30 seconds. Now turn the temp dial to full hot a listen carefully. You should hear a difference in sounds as the blend door sweeps through its full range.

If it is working and the engine is fully warmed up feel the heater hoses where the pass through the fire wall. One should be very hot and the other should be pretty warm. If one is hot and one is significantly cooler than either the heater core is plugged or there is air in the heater core causing a block in flow.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

most likely a stuck heater tap,but may involve vacum or elec controlled trap doors in HVAC system

What is year--make--model? Your saying the blower motor works but only cold air comes out? Does the engine reach normal operating temp? Are the heater hoses hot? If that checks out, have to check temp door under the dash.

try locating the physical tap that connects your heater hoses to the interior of the car. note what position that tap is in before and after you turn up the temp dial inside. whatever connects the dial to the tap may be damaged.

if the tap itself turns then the heater side of the blower may be blocked.

Check the voltage coming to blower resistor with ohmmeter for continuity!

To troubleshoot this types of problem,click the link below :----http://howtobyme.blogspot.in/2012/02/heater-blows-only-from-defrost.html
--------Go through the procedure to confirm the issue.

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Engine Overheats and heater blowing cold?

http://howtobyme.blogspot.com/2011/11/engine-overheats-and-heater-blowing.html

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Heat blows cold on drivers side and hot on passenger side?

http://schematicsdiagram.blogspot.com/2011/12/heat-blows-cold-on-drivers-side-and-hot.html

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No heat on car? http://technoanswers.blogspot.in/2012/02/no-heat-on-oldsmobile-silhouette.html

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Heater blows intermittently and temp gauge goes erratic? http://technoanswers.blogspot.com/2012/01/heater-blows-intermittently-and-temp.html------------Heater blows cold? http://schematicsdiagram.blogspot.in/2012/02/heater-blows-cold.html
---------Car heater blowing warm, but not hot air? http://schematicsdiagram.blogspot.com/2011/12/car-heater-blowing-warm-but-not-hot-air.html-------- Heater/AC blower motor not working?

http://technoanswers.blogspot.in/2012/02/heaterac-blower-motor-not-working-on.html

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A/C, heater, defroster fan, not working? http://technoanswers.blogspot.in/2012/02/ac-heater-defroster-fan-not-working.html Heater problem? http://technoanswers.blogspot.in/2012/02/heater-problem-on-isuzu-trooper.html---------

This will help.Thanks.

Temp blend door actuator possibly .

check thermostat and coolant level

Sounds like there is a crack in the vent that leads to the drivers side, and hot air from the engine is leaking through.

the climate unit has an internal fault