I've seen enough halloween related forum posts complaining about these cheapo 400W fog machines where the pump quits working, but no solutions. Here is one solution:

So I bought one of these 400W foggers a few years ago and haven't necessarily been following the rules: https://www.instructables.com/id/Care-and-Feeding-o...

Last Halloween I tried using this fogger and it wouldn't fog no matter how hard I pushed the button. Fast forward to today when I finally had a few hours to fiddle. After disassembly, I'll spare you the pictures of me removing screws, I found this fogger has a 30DSB-ZJF pump. The heating element still works well, so I am leaving that alone.

Step 1: Pump Disassembly

First I disconnected the.... ooop nope, first make sure it is unplugged and cooled down! Next disconnect the pump from the copper tubing that leads to the heating element. Now the hose from the back of the pump that comes from the tank should be disconnected, not later. Then using an adjustable wrench unscrew the nipple from the front of the pump. Then remove the small plastic piece in picture 4. Next the soul of the pump should be removed (I am not sure what it is called). It may be a bit difficult to remove, that is why it needs to be fixed. Picture 7 shows the plastic piece that needs to be removed, cleaned, and fixed.

Step 2: The Fix

Picture 1 shows the piece fully out. Make sure the washer from the nipple came out, or is least in the right place for reassembly (down inside the housing). Picture 2 shows the problem. After a few years of pumping fog the plastic melted and shrank. There are three bands colors on this piece of plastic...white(the original color of the plastic), light brown, and let's call it brown. Looking at the brown banded areas, notice they are slightly deformed or smaller than the light brown and white areas. Without a way to reshape the plastic it was decided to shove something in there to fix it. "Hey, this 3/8" drill bit just fits!" Boring out the inner diameter to 3/8" now allows the metal soul of the pump to fit tightly yet slide freely. Just what is needed. Make sure to clean out the plastic shavings from the drilling.

Step 3: Reassembly Part 1

Picture 1 shows all the components in the order they go back in. Missing is the washer for the nipple of the white/brown plastic piece. Picture 2 description is as follows. After reassembly but before screwing on the large nipple, the fogger was plugged in and allowed to heat up to where the trigger could be activated. Hold the pump as shown in picture 2 (remember the black and yellow wire have 120VAC to power the electromagnets inside). Pressing the trigger should make the white plastic vibrate something fierce. That is good!

Step 4: Reassembly Part 2

Before reattaching the large nipple, remove the stopper/spring assembly from within. The spring has lost some sprang, so stretch it out a bit, say up to 2". This will help push the inner part of the pump back in after the electromagnets push it out. You know, the pumping action. Put the spring back into the large nipple. Make sure the rubber stopper on the spring lines up with the end of the white plastic and tighten the large nipple back on. Reattach the tube from fog juice tank back on to pump assembly.

Step 5: Testing

Yeah the fogger was still plugged in and up to temperature, so the pump was tested with fog juice. Picture 1 shows the pump squirting fog juice. Insert hopeful Whoo Hoo. At this point the fogger should be unplugged and allowed to cool as the copper tubing is quite warm to the touch. Picture 2 shows the copper tubing reinserted and the nut hand tightened. Picture 3 & 4 shows the fogger plugged back in, heated up, and pumping out clouds of fog. Whoo Hoo!! Then screw the pump back into place and reinstall the cover of the now working fog machine!

As I didn't fiddle with the heater, I didn't try to figure out how it works. I am guessing when that goes out it'll be time to retire the fogger.