I have a 2007 Civic and having an AC issue. The AC blows cold but will not blow on high but for a short period of time. I took to a mechanic and they thought it was the cabin filter but it still is doing the same thing. At first it seems to work fine but as time goes by the Fan drops all the way to Lowest Fan speed but I do not touch the dial.

 

try changing the blower resistor located behind glovebox. my AC would only work on 2 highest settings changed that and i now have all 5 speeds. part is new for about 20$ and it involves 3 screws--good luck

 

The 07 (if it's like the 05) should have a power transistor not a resistor. Generally the transistor is either working properly for all speeds or completely dead. When the fan slows down, measure the voltage across the fan motor. If it's still 12 volts the motor must be bad.