DOESN'T RUN ANYMORE

Check the capacitors. There are two to look for, one on the motor, the other on the PC controller board. 
STEP ONE: Unplug the unit and support it on a table. 

STEP TWO: remove the controller board from the exhaust side of the unit by unscrewing the screws holding the cover to the unit. Unplug the motor wire harness by pressing down on the white retaining clip. They go only one way, but it doesn’t hurt to note which is which. 

STEP THREE: Unbolt the ground wire from the face plate and the whole board should come out. Unscrew the four screws holding the PC board. Look for a little foam pad that will drop out. Remember where to replace it. Screws and capacitor may have blue locktite on them. 

STEP FOUR: Find the capacitor. It’s the part that looks like a tootsie roll, black with two wires coming out one side. It’s between the CPU chip and the big red square block. If it looks bloated, burnt or melted, you found the problem. Replace it with a 1000 microfarad (1000 uf/ 10 volt) ten volt capacitor with a radial lead. About $5 for the part at most electronic parts stores. Careful desoldering the old capacitor to avoid damaging the PC board. WATCH THE POLARITY. There is a negative and positive side. The negative side has a chevron (<) mark and is marked on the PC board. On mine the negative side was nearest the black micro chip and the positive side was towards the red JEFU MPE part. Use a little bolt-tite on the screws of the PC board and some on the capacitor on the PC board to limit vibration. Reinstall the board, plug it in and give it a whirl. 

If no joy, STEP FIVE: Find the motor start capacitor. It is bolted near the motor, black about 1x 2 x 4 and has two red wires coming out of it. Take a battery operated resistance meter on a setting of R x 100 or higher. Charge the capacitor by connection one lead of the tester to one red wire and the other lead to the second red wire. You may have to strip the wire to make contact. Next reverse the leads and you should see the needle jump. Do it a third time incase the first try was discharging. If no needle jumping, replace capacitor. Couldn’t find this locally. May have to by directly from JET Tools. L

Recommend you hard crimp wire splices if cutting off the motor capacitor. .  You can check the windings on the motor too. Check for continuity between the white-yellow-blue-black wires of the motor harness. Any combination should work. If not, motor shot, time for some bigger bucks nrepair.
 
Hope this helps.