If your hot tub blower is not working properly, you can do a few things yourself to troubleshoot. Any major electrical repairs, especially around water, should be done by a qualified professional. Make sure before doing any troubleshooting that you completely disconnect any power to the hot tub.
Checking for Appropriate Voltage
Most air blowers in hot tubs operate at 110 volts, but a few operate at 220 volts. You have to make sure the voltage you are providing to your blower matches the voltage it is meant to run on. If the voltage supplied is too high, you may fry your blower, and if it is too low, the hot tub blower will not have sufficient energy to run properly. You can most likely find this information in your owner's manual.
Checking Your GFCI Switch
The GFCI is a current breaker in your hot tub. It can be switched off or "tripped" if the water is getting into your hot tub blower lines. Your hot tub manufacturer has taken measures to avoid this scenario. Manufacturers usually include a portion of the air plumbing above the waterline as well as check valves that will close when air is not blowing to keep water from entering your line. Check to make sure that a portion of plumbing is indeed above the water line and also that your check valves are functioning properly.
Evaluating the Power to the Hot Tub Blower
Sometimes hot tub problems may be linked to wiring or power issues. You should check the continuity of power in the black wire leading from the blower to the air switch. If power is found, you may have a bad blower unit. If power is not found, you may have a bad air switch.
Checking the Power to the Air Switch
Check the wire leading to the air switch for continuity. If no power is found, you may simply need to replace this wiring. If you find you have power but your air switch is not switching properly, you need to replace your air switch.
Replacing Your Blower
Having exhausted all of the above possibilities, you may need to replace your blower unit in your hot tub. If you are planning on completing this undertaking yourself, make certain that all power to the hot tub unit is set to "Off" and the unit is unplugged for safety.