I have a 10 year old TRAX. The ventilation button does not work at speed 4. In position 4 it turns off the fan.
Asking for help diagnosing the problem. Thanks, Haim

 

When one speed stops working, it is usually the blower motor control module (resistor). You don't say what year it is, but for a 2015 Trax, RockAuto has a number of parts available:

https://www.rockauto.com/en/catalog/...+resistor,6557

That said... this looks NOTHING like any of the blower motor control modules that I've replaced before. Usually they have actual resistors, or a box of electronics of some sort. This one looks like a flat card attached to a connector. It may have traces that act as resistors though, and be flat...

Maybe wait a bit for someone else to chime in and confirm what I am thinking.