P1 not running is obviously a problem ... whether it's related to the non-start issue remains to be determined.

The drawer-closed sensor is optical. Does the lid close when starting a (non-diagnostic) cycle? It won't if the drawer is not sensed to be closed. Also, assuming the auto-power function is engaged, does the drawer power turn on upon opening (when it's off before opening)? If yes, then the sensor should be OK.

What Fault Code do you get in Diagnostics?

Regards to board numbers, F&P may make engineering/software revisions during the course of production without changing the model number. Each board revision has a different number. Most are compatible, a few are not. Look up your both your model number (and note the Product Code which is a separate number, should be on a label on the unit, possibly on back of the cabinet) and the original board number at appropriate parts sources and it should cross-reference to whatever is the current replacement.

> What Fault Code do you get in Diagnostics?

No fault codes as far as I can tell. I've dealt with no-fill and flood faults before, and this behavior is different.

> Does the lid close when starting [when its misbehaving]?

> does the drawer power turn on upon opening [when its misbehaving]?

Looks like no to both, but its intermittent- does that make sense?

Sometimes I can get the cycle to start and all appears normal, but it stops with the same symptoms after a few minutes. Here's a full sequence of a test I just ran:

------------------

Power off.

Open drawer, power comes on.

Close drawer, press start, cycle starts.

2 minutes later, cycle stops with a single long beep.

Press start, and cycle fails to start. It makes the dit-dit-dit-daa alarm sound instead.

Press power button, power shuts off.

Open drawer, power stays off.

Leave drawer closed with power off for 2 minutes.

Drain pump starts all by itself and runs for a bit, then the power comes on with a happy, 4 beep, "I woke up" sort of sound.

Push power button, power goes off.

Open drawer, power stays off.

Wait about an hour, open drawer, power comes on.

Repeat as above.

(The second drawer does the same thing, but you have to wait longer)

Nice to meet you, by the way- I've read some of the stuff you've written to others and it's been tremendously helpful to me already!

SOLVED!

Ok, a friend of mine and I got a hold of a webcam that can see IR. (many of the cheap-o ones can) and we verified that the IR LED was flashing when the system worked, and that it stopped flashing when the system was misbehaving. The LED is behind the lower of the two prisms on each drawer.

That means the logic board needs replaced. That's available for purchase here:

https://www.letstalkparts.com/Control_523456_p/523456.htm

And, just as you said, they list that this board replaces mine and a few others:

522841USP, 522946USP AND 528356USP

So there you have it. $150, unless you're handy with electronics and somewhat adventurous. Which I am...

I won't give detail here, because if you're qualified to do this sort of thing you'll figure it out. Also- the board runs directly off line voltage, so there's enough energy in there to hurt you if you mess up. All the normal sensitive electronics precautions apply.

With that disclaimer, and the caveat that I figure I had nothing to lose once I was sure the board needed replaced anyway, here's the $5 solution:

We tried to fool the sensor with lots of different light sources, and none of them worked. We also tried soldering in a red LED. The red LED flashed, which proved to our eyes that the old LED was the problem, but it still wouldn't work.

So we went to Walmart (everything else was closed) and bought a $5 universal TV remote. Tore it apart and removed the IR LED, and used that to replace the old one. The IR mount on the board is close to the heat-sink for the power supply, so be careful. And obviously unplug everything before getting in to the board.

Reconnected the power and all is well- I don't know how long the fix will last, but the short test cycle completed as normal, and we ran both drawers overnight and found clean dishes in the morning.

Huzzah!

Nice fix! I read a tip a few months ago, regards to checking if a remote control is working, that some digital cameras can detect IR. The problem did seem like the IR sensor circuit, except for the P1 failure since the HO diagnostics will run the pump with the drawer open.

P2 (drain pump direction) runs with the drawer open. You actually wrote an answer to someone else saying that P1 (wash pump direction) only runs when the drawer is closed. That fact was instrumental in figuring out my problem.

Hmm. Interesting. I may have been citing from service docs on that statement. I checked my DD603 couple mins ago, it does run on both P1 and P2. Difference likely related to software revisions.