E4 and E5 codes explained finally! E4 means motor is not spinning right, or reaching correct RPMs. E5 means heater in not working right. I will provide more detains next.
I had an AM05 which stopped working and it was showing E4 fault code and power light was blinking red. Occasionally as I turned it on motor would spin up for a second and then stop and fault code would display. Most of the time motor did not move. WARNING! I am an electrical engineer and have fixed countless things in my life, and I can say, taking this unit apart and putting it back together was very difficult. Do it at your own risk and of course, MAKE SURE POWER IS REMOVED WHEN WORKING ON IT.
First, remove the base ring and remove big screw in the middle. Next, disconnect the plastic white ring connected to the oscillating motor drive shaft. This requires removal of a C-Clip. (don't lose it, as it's likely to fly when being removed). Now pry apart the bottom section from the rest. Be careful as there are connecting wires all still there. Next, tilt the fan forward all the way and that will expose 4 screws in the rear, and when tilted the other was, two screws in the front. Remove them all. Now, disconnect connectors and start separating parts. Here are a couple of pictures I had taken.
Of the two identical 6 or 7 pin connectors one has all red wires and the other is multicolor. When I disconnected the red one, the fault code went to E5. The red one goes to another board that has the heater circuit, so I deducted that E5 means either connections to the heater are bad, or heater is bad. I reconnected the red one and E4 came back. I disconnected the multicolor one and nothing happened, which told me the problem is there. I traced the wires and they were all going to the motor, which is further up the assembly. Getting to it was a real pain. To free the multicolor cable, you have to separate two rubber seals that allow the wires to move through an opening. If you can manage this, you can slowly get to the motor. When I turned the impeller I noticed that it was dragging, which explained the E4 code. When I turned it upside down motor spun freely and the fault code went away. So, I knew I had to fix the dragging problem, which was easy. Then putting it back together was a real pain. I recommend taking lots of pictures to remember what came from where. NOTE: There is thermal grease inter a metal heat sink. Make sure you don't wipe it off. It's essential, or heater semiconductors will overheat and fail. Also, MAKE SURE WIRES AT THE BOTTOM SECTION NEAR THE SWIVEL MECHANISM ARE DRESSED AS THEY WORE ORIGINALLY! Otherwise, they will rub and cam cause a fire. As you probably already know, there was a recall on these.
Anyway, hope this helps people. I have gotten so many great tips off the internet, I figured I had to contribute some as well.