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I recently got this electric dryer used. The previous owner said that it only works for the first load of laundry and then quits. Upon first plugging in the dryer, I get the following lights as seen in the photo below. The only buttons that don't work are wrinkle prevent, signal +/-, start/pause, and off. The rest of the buttons light up and perform their normal function, with the exception of the air fluff and wrinkle release buttons. These buttons perform their function, but do not light up. Needless to say, I am unable to get the dryer to actually start. I asked around and some folks have said that it's probably the main board and that the replacement cost would be upwards of $300: $200 or so for the part and $100 for a professional technician to flash the ROM. I'm just looking for some second opinions before I start throwing money at this thing. I am pretty electronically/mechanically inclined, so if checking things with a meter or soldiering will get me closer to a fix, just let me know. I'm not afraid to crack the case on this machine if it means I'll save some bucks. 
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Looks like that was just the number for owner's manual. The correct model number for the dryer is MDE5500AYW.
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Whew, lots of reading there. Anyways, I went into service mode and checked for diagnostic codes but got none. So I checked the continuity of the supposedly dead buttons on the J7 connector and they all work.
So then I went and checked the voltages on the board to see if they were correct and this is where things began to not check out. When measuring the heater relay internal output between P1 and BB1(1) I got 0v. The same happened when I tested the motor input at BB1(2) and BB2(3). Also, all of the J4 pins were dead.
So what could be the cause of these pins being dead and why did they not show up as diagnostic codes?
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The unit will not run at all so I would not worry about the heater circuit.
The motor must run for you to get heat. the centrifugal switches on the motor are activated when the motor gets close to operating speed and one of them connects in L2 voltage for the heater. This ensures that there is only heat when ther is air flow.
[COLOR="Blue"]When measuring the heater relay internal output between P1 and BB1(1) I got 0v. [/COLOR]
If the motor is not running then this is what you would expect as the motor's centrifugal switch should remove power from the heater circuit re: the L2 side of the line.
[COLOR="Blue"]The same happened when I tested the motor input at BB1(2) and BB2(3).[/COLOR]
I traced these lines back and unless I messed up they both go back to the Normally Open (door closed) contact on the door switch so they also should be 0 volts.
[COLOR="Blue"]Also, all of the J4 pins were dead.[/COLOR]
By dead I assume you mean no voltage.
A couple things here.
The voltage for the thermistor is probably DC not AC.
Same applies to the sensor bars.
Also they will be relatively low voltage.
The circuit is a bit of a pain to read/follow.
So I would print a copy of the wiring diagram and then trace out the motor/start circuit so it is easier to follow.
it is Neutral , Door Switch closed contacts , Drive Motor start and run windings , the two Thermal Fuses , BB1-2 , Motor Drive Relay contacts , BB!-1 , L1
I would unplug the unit and using resistance work your way back through the motor circuit to BB1-2.
Connect one meter lead to Neutral and leave it there.
Note that I am not sure what the motor windings should be other than they will have some resistance.
If OK
Check that the wire from the door switch closed to door sense (BB@-3) has continuity.
FYI: They do not monitor the relay outputs so you will not see an error if one of then is not closing or if it closes but it's contacts are bad. |
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OK, so I did some more checking and everything appears to be normal with the exception that I now get the trouble code 02; meaning that the drier is too cold. So, I plugged the outside vent and I'm waiting for it to heat up to see if that changes anything.
Also, since the start, off, and signal +/- buttons don't do anything even though they tested fine, wouldn't that point towards a bad main board?
If I do end up replacing the board: do I need to install the software on it, or is it a just simple uninstall/reinstall of the part?
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[COLOR="Blue"]Also, since the start, off, and signal +/- buttons don't do anything even though they tested fine, wouldn't that point towards a bad main board?[/COLOR]
Yes
[COLOR="Blue"]
If I do end up replacing the board: do I need to install the software on it, or is it a just simple uninstall/reinstall of the part?[/COLOR]
You should just be able to install the board. |
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So, I ordered a replacement control board and now the drier starts up and turns by itself. Pressing the off button turns off the display but does not stop the motor. The only way to stop it is to open the door or pull the plug.
What have I wired up incorrectly? The heater and motor relays on the board or the main power inputs from the wall?
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[COLOR="Blue"]What have I wired up incorrectly?[/COLOR]
I cannot say but I do not think that you can mis-wire it.
[COLOR="Blue"]
The heater and motor relays on the board or the main power inputs from the wall?[/COLOR]
The relays are on the control board.
Unplug the unit and check across the motor relay contacts at the board output.
It should be infinite ohms (open).
If 0 ohms (closed) then the motor relay contacts are welded together and the board is defective.
Disconnect the wires to this at the board. This ensures that you do not read an alternate/parallel circuit path.
Always a possibility that you received a defective board that it is always activating the motor relay |
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