We installed a new toggle light switch and new ceiling exhaust fan timer switch for the bathroom. Now when we use the hair dryer the exhaust fan surges on and off.
It appears that you have one of the wall outlet wires attached to one of your toggle switches or even your fan timer switch. You will need to verify your wiring and check to make sure you have all the wired firmly secured and in the right place. Make sure an open wire isn't touching another one and if you do have an open wire use a wire cap on this. it is dangerous to leave it open and not capped.
If both are on the same circuit, it may be overloading. You may need two circuits.
Outlet for the blow dryer needs to be on a different circuit.