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tsmith35  
#1 Posted : Monday, November 24, 2014 12:57:14 AM(UTC)
tsmith35

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Hi again!

Okay, so I have a Whirlpool WED4900XW0 electric dryer. Yesterday afternoon, the dryer stopped in mid-cycle. I observed the following:

With door open or closed, the heating element came on
With door open or closed, the drum would not turn
When the heating element was on, turning the dial to "no heat" turned off the heating element

I checked the motor centrifugal switch, and it worked fine. Then I checked for continuity between the heater wire downstream of the switch and ground. It was not open. The combination made me suspect that the heating element was in contact with ground.

I pulled the back panel and removed the heating element. Sure enough, one of the ceramic insulators had turned, letting the heating element contact the metal body of the element holder. I corrected the situation and put everything back together.

The problem now is that neither the motor nor the heating element starts when the door switch is closed, heat level is set to anything but air dry, and the start button is pushed. When I press the start button, I can feel a relay pull in, and when I release the door switch, I can feel a relay drop out, but no heat and no drum movement.

I suspect a fuse or overload switch is stuck. Or perhaps the short to ground caused damage to some part, but I'm not sure where to look first.
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denman  
#2 Posted : Monday, November 24, 2014 2:36:52 AM(UTC)
denman

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Here are your parts
Parts for Whirlpool WED4900XW0 Dryer - AppliancePartsPros.com

See the attachment for the tech sheet

[COLOR="Blue"]The problem now is that neither the motor nor the heating element starts when the door switch is closed,[/COLOR]
The heating element should not come on until the motor is running due to the motor's heat centrifugal switch.

[COLOR="Blue"]heat level is set to anything but air dry, and the start button is pushed. When I press the start button, I can feel a relay pull in, and when I release the door switch, I can feel a relay drop out, but no heat and no drum movement.[/COLOR]
I am not sure that I am interpreting the above correctly.
Are you saying that the unit rums correctly when set to air dry?
If yes then set it to air dry and unplug the unit.
Check BU to BK and T to W at the timer both should be 0 ohms.
Then set the timer to heated dry and again check the above.
They should stay at 0 ohms.

[COLOR="Blue"]I suspect a fuse or overload switch is stuck.[/COLOR]
I doubt this as it would also not run in air dry.
The motor circuit is the same for air and heat dry other than where in the timer cam the contact levers/actuators are.

[COLOR="Blue"]Or perhaps the short to ground caused damage to some part[/COLOR]
If you had a short it should blow a breaker
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tsmith35  
#3 Posted : Monday, November 24, 2014 9:48:24 AM(UTC)
tsmith35

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Originally Posted by: denman Go to Quoted Post
See the attachment for the tech sheet
Thanks! That should help quite a bit! :)

The problem now is that neither the motor nor the heating element starts when the door switch is closed,
The heating element should not come on until the motor is running due to the motor's heat centrifugal switch.
It was coming on since it had shorted to ground halfway along the element's length, so 120V was running from L1 to neutral/ground. The resistance of the element prevented it from being a dead short, so it was heating up half of the element (the centrifugal switch is on the L2 side).

heat level is set to anything but air dry, and the start button is pushed. When I press the start button, I can feel a relay pull in, and when I release the door switch, I can feel a relay drop out, but no heat and no drum movement.
I am not sure that I am interpreting the above correctly.
Are you saying that the unit rums correctly when set to air dry?
If yes then set it to air dry and unplug the unit.
Check BU to BK and T to W at the timer both should be 0 ohms.
Then set the timer to heated dry and again check the above.
They should stay at 0 ohms.
Well, there were two scenarios, and the motor hasn't run in any of them:
1) The shorted heating element would come on with the door open and with the temperature selection set to anything but air dry - fixed by repairing the short
2) Now that the short is fixed, neither the motor nor the heating element come on regardless of any setting. Since the centrifugal switch works (tested with my meter), it appears that this is due to lack of the motor turning. I just need to figure out why the motor isn't turning.

I suspect a fuse or overload switch is stuck.
I doubt this as it would also not run in air dry.
The motor circuit is the same for air and heat dry other than where in the timer cam the contact levers/actuators are.
The thermal fuse goes to the motor only, so I thought I'd check that first.

Or perhaps the short to ground caused damage to some part
If you had a short it should blow a breaker


So, I guess now I'm just trying to figure out why the motor won't start. I suspect that the previously-shorted element was backfeeding some component and caused additional damage, but I'm not certain. Headed to the dryer with my meter for round 2. :)
tsmith35  
#4 Posted : Monday, November 24, 2014 11:53:00 AM(UTC)
tsmith35

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Aha! Initial failure of the heating element (shorted to gnd/neutral halfway along the length of the element) caused the thermal fuse to blow, since there was no air movement while the dryer motor was off. The short allowed power from L1 to go to ground across the element regardless of the door switch and/or centrifugal switch position, so the thermal fuse did it's job and blew.

Tested by jumpering the thermal fuse temporarily. Everything operated after that. Jumper is removed, and I'm going to pick up a replacement fuse or two. Thanks for your help!
denman  
#5 Posted : Monday, November 24, 2014 11:57:38 AM(UTC)
denman

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OK that is different from the way I was interpreting it.

First thing to check is the thermal fuse on the blower housing.

If it is 0 ohms then try the following:
Unplug the unit.
Attach one meter lead to the line cord's Neutral and leave it there(tape or clip it on).
Meter on it's most sensitive scale also short the meter leads together before starting to see if there is a 0 offset.
Now work your way back through the motor circuit.
Door closed and timer set to mid scale timed dry.

Both sides of the door switch should be 0 ohms.
T and W on the timer should be 0 ohms.
5M on the motor should b 0 ohms.
4M on the motor should be a couple ohms (motor windings)
Both sides of the thermal fuse should be a couple ohms.
LBU (light blue) wire on the start switch should be a couple ohms.
Also the other side of the start switch (actually it is a relay) contacts.
BU and BK should be a couple ohms with the start switch activated.
Also L1 on the line cord.

There that is the motor start circuit.
tsmith35  
#6 Posted : Monday, November 24, 2014 12:23:25 PM(UTC)
tsmith35

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Yep, you nailed it! Thermal fuse gave its life to keep the dryer from catching fire. :) Handy little bugger.

By the way, I found the schematic taped inside the console. Exact same number and revision as what you sent, but I like the PDF better since I can zoom in. Thanks a bunch for your help!
denman  
#7 Posted : Monday, November 24, 2014 1:09:38 PM(UTC)
denman

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You are welcome

And thanks for getting back to us. Now when others search for a similar problem they will see what actually worked instead of just suggestions about what could be the cause.
tsmith35  
#8 Posted : Monday, November 24, 2014 4:33:55 PM(UTC)
tsmith35

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Okay, new thermal fuse is in place and working fine. I cleaned all the lint and dust out of the dryer while I had it open. I also slightly adjusted the orientation of the L1, L2, Neu and Gnd ring terminals. Whoever hooked up the dryer cord originally had left very little space between the wires, so I opened up the spacing a bit to help reduce the chance of any unintentional contact. Thanks again!
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