Whirlpool Duet Dryer "Control Locked"

WhirlpoolWhirlpool DryerModerate⏱ 1 hour

Инструкция на английском (оригинал iFixit). Непонятные термины — в разделе «Основы → Словарь».

People have been encountering a single light on their Duet dryer labelled “Control Locked” accompanied with their dryer being unresponsive to any button presses. Online solutions suggest pressing and holding the “End of Cycle Signal” button for 3 – 5 seconds, or unplugging or turning off the breaker to the unit for a period of time. This sometimes works. Detailed here is a technical explanation of why this happens and how to perform a board level permanent repair for this failure. This problem can be fixed using only a Phillips screwdriver. Read on to see how and why. Schematics are attached. Applies to models GEW9250ML, GEW9250ML0, GEW9250PL, GEW9250PL0, GEW9250PW0, GEW9250PW, GEW9250PW0, GEW9250SU, & GEW9250SU0 and part numbers 8559431, 8558743, WPW10128437, W10128437, & PS11748687.

🧰 Tools

Phillips Head Screwdriver: Size PH1
Soldering Iron
1/4" Nut Driver
T8 Torx screwdriver
multi-meter to measure voltage

ШагиSteps

Background

TLDR: Replace the green LED.
“Control Locked” is not an error status but a feature. You turn it on or off by pressing and holding the “End of Cycle Signal” button. Below this button it clearly states “Hold for 3 Seconds to Lock / Unlock Control.” Its intended purpose is to prevent unwanted changes to the dryer’s settings during operation.
The problem is repeatedly finding clothes not dry and this light on. Again. What is causing this light to randomly come on? In one case it was a bad LED, D20 for “Cycle Complete.” Conspicuously, this is the only green LED and it is also physically smaller than all of the other LEDs.

Technical Explanation

Normally, when you press the “End of Cycle Signal” button, it connects pin 12 of cable P1 to pin 2 of cable P2. When the microcontroller polls pin 12, it senses it on pin 2 if the button is pressed. If it senses this for more than three seconds, it turns on (or off) “Control Locked.”
If D20 is shorted, when pin 12 is polled the current travels through steering diode DD6 like normal, then flows improperly backward through D20 (The “Cycle Complete” LED). It then flows through segment D1 of the right-hand seven-segment LED display and then on to pin 2. This voltage now present on pin 2 is sensed during the poll.
And now it is like the button is being continuously pressed. The microcontroller then dutifully turns on the “Control Locked” feature. The LEDs for Sensing, Cool Down, Wrinkle Guard, Louder, Softer, and Off could also cause this problem if they failed in the same way.

Repairing

This can be repaired by replacing LED D20 or simply bending it back and forth until it snaps off the board. To diagnose if LED D20 is defective, there are two methods.

Diagnosing, Method 1

The first method is using the diagnostic mode —if you can catch the dryer in a moment of normal operation. Start with the dryer off. If it is not off, just hit the “Pause Cancel” button. Enter diagnostic mode by pressing the following button sequence: “More Time”, “Less Time”, “More Time”, “Less Time” within 5 seconds.
All LEDs should now be on and 88 showing in the “Estimated Time Remaining” display. Are all LEDs fully illuminated? Especially the green “Cycle Complete” LED. Sensing, Cool Down, Wrinkle Guard, Louder, Softer, and Off can also be suspects. If they don’t look right, they should be considered suspects.
The second diagnostic method uses a multimeter that has a diode testing function and does not require removing the control panel but does require access to the Machine Control Electronics.

Disassembly

Unplug the dryer from the electrical outlet.
Remove three screws from the top rear of the machine. These screws have plastic washers behind them that may stay stuck to the machine and are easy to get lost.
They are 1/4” hex headed screws that can be removed with a nut driver or a Phillips screwdriver. Many multi-screwdrivers have a 1/4” barrel that holds the bit. Simply removing and setting aside the bit allows you to use the multi-screwdriver as a nut driver.
The top or lid now slides back and lifts off.
When facing the front of the machine, the Machine Control Electronics is under a metal cover that runs from front to back on the left-hand side. There are three sheet metal screws on the top left edge of the machine that hold this in. Remove these three screws.
Rotate this cover as well as the attached circuit toward the dryer’s drum, exposing the circuit and its connectors.
Disconnect the two white ribbon cables. There is a latch that needs to be pressed toward the ribbon to release the connector. This latch is within a plastic shroud that does not depress. You need to depress the latch with something that fits in between the shroud while simultaneoously pulling the cable out of the connector.

Diagnosing Method 2

Set the multimeter to the diode testing function. It should be the symbol of an arrow or triangle pointing into a bar. On some multimeters this is a secondary function when set to this position and you have to press a button to put it into the diode testing mode.
There are two white flat ribbon cables that go between the Machine Control Electronics board and the Console Electronics board. One is wide (P1) with 14 conductors and the other is narrow (P2) with only six conductors.
On the Machine Control Electronics board end of these cables, P1 and P2, put the positive (red) lead on pin 2 of cable P1 (the wider cable) and the negative (black) lead to pin 1 of P2 (the narrow cable). There are rectangular holes on the side of the cables that should allow the tips of the meter probes to make connections through.
Dupont connector pins have the same pitch and are nearly the same size as these connectors and are handy to facilitate connections for testing.
The meter should now read a forward voltage drop of around 1.7 volts. Reversing or swapping the leads, should read infinite, or OL (out of limits).
A basic meter self-test is to short the leads together; it should read 0 volts.
You can test all the LEDs, buttons, and the cycle selector switch with this method using the Forward Voltage Drop Table that is included with the schematics here. If you identify failed components, proceed to further disassembly.

Further Disassembly

Be careful not to damage the ribbon cables as you pull them out. Note how they are routed so you can reinstall them properly.
There are two methods to remove the Control Panel, the easy way and the hard way. The easy way is to remove two screws at the top left and right sides of the front of the machine.
Then, with the door open, unhook the bottom of the panel from the machine and lift straight up. It lifts out of slots on both sides that you need to remember to return it to during reassembly, or it will not fit flush with the front of the machine.
There are four screws holding the panel to the metal bracket you just removed. The harder method is to remove only those four screws, leaving the bracket in the machine.
Remove those four screws to remove the metal bracket and expose the rear of the Control Panel. Remove the cables by operating the connector latches as documented at the bottom of Step 5.
There are 17 T8 Torx screws that hold in the three boards that make up the Control Panel. For PCB1, remove the two screws that hold in the selector knob board and lift it out. Note that the shaft from the selector knob has a “D” shape to it that fits into a “D” shaped hole on the selector knob board. Get this aligned during reassembly.
Remove the board or boards that need repairs as determined in Step 4, Diagnosing Method 1 or in Step 6, Diagnosing Method 2. Replace the needed LEDs or buttons.
END OF "CONTROL LOCKED" GUIDE. When working with the boards, if you get the LEDs bent over and must bend them back for reassembly, they will eventually break off if you do this too many times. Be careful not to bend the LEDs. Diodes are a polarized device, so instill new ones with the correct orientation.

Other, Intermittent Problems

Intermittent problems have been traced to connectors on the Machine Control Electronics board. Putting the machine in diagnostic mode and gently pulling upward on connector P2 would cause LEDs to come on and buttons to resume working. This is likely caused by a cold solder joint.
It is probable that past repair efforts that seemed to temporarily fix the machine were actually unintentional consequences of manipulating this connection while working on the machine. The matching washing machine has a known cold solder joint failure point.

Repairing Intermittent Problems

Remove the Machine Control Electronics board by doing the following:
Disconnect the two white ribbon cables following the instructions above.
There is a zip tie that holds a wiring harness to the metal shield near the yellow power transformer. Detach this zip tie from the metal shield by squeezing together its anchor snap-ins and pulling the anchor out of the hole for it in the metal shield.
Unplug the five-pin black plastic connector next to the yellow transformer from the circuit board by squeezing its retaining clip while pulling it out.
Unplug the two heavy-gauge black and red wires next to the previous connector. These are crimp-on terminals and should pull straight off.
Unplug the remaining white connector by pressing in the clip next to the edge of the circuit board while pulling up.
The Machine Electronics with its shield should now be able to be removed from the machine.

Removing Circuit Board From Holder

Remove the one hex headed screw that retains the circuit board.
Depress the plastic retaining clips at the edge of the board and tilt it up and out of its plastic holder.

Repairing Connectors on the Machine Control Electronics Board

This board is covered with a thick, smooth, and shiny conformal coating. There are no solvents that remove it. The coating’s manufacturer recommends micro abrasion or heat to remove it. You will need this coating removed from the pins of the connectors you are working on (P1 and P2).
This is fairly easy to do. Simply, patiently and gently, rub around the pins with a hot soldering iron. This should turn the coating into a grayish white powder. It can then be cleaned up with a variable-speed rotary tool, like a Dremel, using a nylon rotary brush. Once the conformal coating is removed, unsolder the connectors.
Replace them with new or reuse them after scraping, sanding, or filing off any oxidation on the parts of the pins that are be going to have solder on them.

To reassemble, follow steps 7 and 5 in reverse order.

«Whirlpool Duet Dryer "Control Locked"» — автор Prof. Mayhem, iFixit, лицензия CC BY-NC-SA 3.0. Показано без изменений. Открыть оригинал и комментарии →