[johnson2511]

Hello everyone, I need some help. My 2018 Corolla will not defrost. I can get my windshield partially defrosted but all other windows turn to fog. I had the dealer look at it and they tell me that I need to replace the Damper sub serv assembly. What is this and what does it do? Where is it located? Thanks

 

[TeamYoder]

A damper servo sub-assembly is a motor that controls the movement of one or more doors in your HVAC system. There are several damper servos that control separate doors. For example the recirculation damper servo moves the door that selects either fresh air or recirculated air and can be found behind the glove box. On the other hand the air mix damper controls the amount of air that passes over the heater (and therefore controls the temperature of the output air) and to get at it you must remove the heater box, which involves removing a large part of the dash.

 

[johnson2511]

A damper servo sub-assembly is a motor that controls the movement of one or more doors in your HVAC system. There are several damper servos that control separate doors. For example the recirculation damper servo moves the door that selects either fresh air or recirculated air and can be found behind the glove box. On the other hand the air mix damper controls the amount of air that passes over the heater (and therefore controls the temperature of the output air) and to get at it you must remove the heater box, which involves removing a large part of the dash.

Team Yoder,

Thanks for the info. My heat is good. I just cent get it to go the right place. I was told that my fresh air and cabin air door is stuck. DO you know where this is located? You said that there are many servo assemblies. I talked to many Toyota guys and they tell me that its rare for this to go bad on a 3yr old car. Could something else be holding this up? Thanks for your help. I'm stuck cause the dealer wants $3000 to replace this.

 

[TeamYoder]

You can find the fresh air/cabin (recirculated) air door (damper) behind the glove box. The heater box assembly is the large black structure behind the glove box. The fresh air/cabin air door is in the upper right of the assembly. When operating properly, you should see the rotate forward/backward as you switch between fresh air and cabin air modes. The servo for that door should be to the left of the door.

You are correct that a failure in a three year old heater box is very uncommon. It is possible that something has gotten in the way of the door or mechanism. I have heard of situations where objects have fallen down the defrost air vents by the windshield and blocked a door from moving. Watch how the door moves when you toggle between the two modes to see if you can determine if something is preventing the door or the mechanism from operating properly. If that is your issue hopefully it is fairly easy to remove the blockage and the door is able to resume normal operation.