Samsung Dishwasher Drying Fan Replacement

The Samsung dishwasher (model DW80K7050US/AA 03) that Came With The House fails immediately after entering the Dry part of the cycle: a relay in the control PCB under the door goes doink, all the LEDS go off then on again, the countdown timer stops changing, and that repeats as long as you like.

After considerable listening & pondering, I decided one event early in the Dry cycle involved starting a fan to vent the steam out of the interior. The wiring diagram shows the fan has a Fault wire: perhaps the fan has failed.

The maintenance manual shows different fans in three different places, although the control board has a connector for only one. By process of elimination, I found the fan atop the cabinet:

The cable from the fan in the vented compartment on the left burrows under the gray duct, around its back side, and plugs into the small white connector on the right. You must ease the cable from a row of hooks guiding it around the back of the duct, which requires slightly lifting the duct.

Unhook the two metal straps, remove four screws from the black vent, and lift it off the top to reveal the duct outlet pores:

Remove four more screws, lift the fan duct assembly just a little bit, and pry open three latches around the fan compartment with a consumer electronics case-cracking tool:

The new fan (on the right) looks very much like the OEM fan (on the left), even though it’s the $15 version rather than the $150 version you might buy from similar randomly named sellers if you were so inclined:

Detach the old fan & its cable, drop the new fan in place, snake its cable, plug its plug, and install All The Things in reverse order.

Unfortunately, after shoving the dishwasher back into its cubby, the new fan didn’t change the failure at all.

I hitched the old fan up to the bench supply and it spun just like it should. Wiring the Fault wire to a 5 V supply through a resistor shows it’s the usual tachometer signal pulsing as the rotor spins.

Which means the next step requires more pondering and PCB probing. The failure is too consistent to be a Heisenbug, but maybe something shook loose in there.