Level of DifficultyA Bit Difficult
Time to do repairMore than 2 hours
Age of Appliance1 - 4 years
Maytag Ice2-0 French Door refrigerator
Our refrigerator started slamming the icemaker door open and shut one evening. Investigation of the card behind the icemaker control panel (the LV control card) on the left-hand door revealed that the +12 volt supply that the card receives via J1 pin 3 was running at about 7 volts. As part of this investigation, I found that a wiring diagram for the fridge is in a sticky envelope behind the kickplate/grill at the bottom front of the 'fridge.
I was confused for a while because the +12 volt supply is floating, so measurements against the 'fridge frame gave very strange results. When I figured that one out, I got consistent results by measuring against J1 pin 1.
I disconnected J6 from the HV control card, located at the back of the 'fridge, and found that the +12 volt supply recovered to about 11.9 volts, so I suspected that the problem was that it was being loaded down by something. This supply gos to three places...the icemaker fan, the LV control card, and the evaporator fan (in some units)
I eventually found how to access the connector that feeds the icemaker, and disconnected it, in order to eliminate the ice fan from the supply. This made no difference, and the resistance across the supply was now 2800 ohms with J6 disconnected. I also noted that the two smoothing capacitors (C12 & C13) on the HV control card were getting hot...probably due to a high ripple current. As a load of 2800 represents a load current of only 4.3 mA, I concluded that the fault was on the HV card.
The +12 v supply is generated by an AC/DC rectifier directly off the 115 volt supply, giving a primary voltage of nearly 300 volts DC. This is chopped by a little horror of a device called a TOP247. It generates an AC waveform and drives a little transformer to generate +12 volts. This sort of circuit can be highly unstable, and it probably went into a high frequency mode, chopping at several megahertz.
Replacing the HV control card solved the problem. I have retained the card, and I intend to reverse engineer it's schematic, then try to repair it. The card cost about $150, but the actual defective component is unlikely to cost more than a few dollars, and I have a suspicion that the two electrolytic capacitors (C12 & C13) may be the cause.