Fan works fine but only cold air comes out
Does the coolant temp guage say the coolant is the correct temp? If the thermostat is stuck open the coolant will never heat up enough to be able to transfer heat in the heater core. If the car's coolant temp is fine and the coolant level is correct, your heater core may be clogged. This would happen due to not flushing coolant regularly and allowing corrosion to build up in the car preventing heat transfer. There is also a heater control valve that controls coolant into the heater core. If it is stuck closed, no hot coolant can make it into the heater core.
Make sure there are no leaks in coolant system, thermostat is working correctly, radiator cap is holding pressure, coolant level is full. If all that is good, you mave have a problem with the heater control valve, or the heater core itself. I
The heater core is like a little radiator that hot coolant flows through transferring heat to the air that blows across it and out the vents. If hot coolant can't find it's way in there, you'll never get hot air.
I really hope this helps, good luck.
Could be the diverter valve. It's the one located near the firewall
in the engine bay. The valve is in-line on one of the two coolant hoses that run through the firewall
SOURCE: Heater blows cold, and fan switch only works on 4 and 5
working on 4 and 5 speed that the resistor that broken cold air you got to move the selector to see the motor that move the trap hot and cold sometime when the motor was not move to the hot side for a long time its jam the motor on the passager side under dash put to hot and gently tap the motor tanks pierre
SOURCE: 03 jetta heater
Sure sounds like a blend air door problem. The rotary temperature knob moves a cable that moves the blend air door. There is a bushing in the housing that likes to break and will either leave the door closed no heat or open heat when a/c is on. TSB 8506-01 covers this problem.
A/C - Can't Adjust Temperature Output Control
85 06 01
July 11, 2006
2012432
Affected Vehicles
Condition
HVAC, Temperature Output Control Cannot Be Adjusted
Customer states cannot adjust temperature and/or A/C is not cold.
Technical Background
The blend door control lever moves freely, but the blend door does not operate.
A bushing that fits on the lever may have a broken tab/clip, -arrows-, as shown.
This tab/clip may cause the bushing to fall out of the fresh air housing which can result in the door becoming inoperative and result in undesired air temperature.
Production Solution
No production change required.
Service Procedure
Tip:
In the past the entire fresh air housing was replaced because the bushing was not available as a separate part. The bushing is now available as a separate part.
The bushing can be accessed from under the center console.
^
Remove the panels near the foot wells at the passenger side of the console, -arrows-, as shown.
See Repair Manual, Body-Interior, Repair Group 68 - Interior Equipment for removal procedure.
^
This will expose the location of the control lever, -arrow-, as shown.
^
Re-bolt a new bushing onto the lever, -arrow-, as shown.
^
Re-insert the bushing with lever onto the blend door until it is firmly secured in the housing.
Tip:
A mirror can be used to aid in identifying the orientation of the blend door when re-securing the bushing in the fresh air housing, -arrow-, as shown.
^
Reinstall panels.
Hope you are good at working in tight spots and with mirrors. I just did this job 2 weeks ago. It took 1 hour and was really a pain in the B==t working upside down with a mirror through a 1 inch hole. Hope this helps and Good Luck Happy New year and thanks for using FixYa.
SOURCE: My 1999 Ford F150 Heater only blows out cold air
guys have you checked for a vaccum leak????? there is a little plastic ball with a vaccum line going to it that controls the outside air coming in. check for a leak in this line
SOURCE: The rear heater does not generate heat - only cold air in vents
does front air work properly? for heat i mean?.. the blend doors are suspect as well as the heater hoses to the rear core and its heater valve.. possibily the control head is to blame or?, but i cant tell from here
SOURCE: Heater blows cold air
If the "Heater In Hose" gets hot, and the "Heater Out Hose" does not get hot, than either the Control Valve is sticking closed, or your heater core is plugged up with ****!
Have you used "Barrs Leak" or a simular product for a radiator leak? That will sometimes clog the heater core.
I have a 1993 Grand Cherokee, which "Normally" throws very hot air out of the heater, but lately sometimes it only throws warm air, till I make my first stop, than it gets hot.....all because the heat control valve is hanging up.
Low water in the radiator will also cause a heater to not work.....if the water level is too low to circulate to the heater.
XRM
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