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george.henne  
#1 Posted : Sunday, January 30, 2011 10:21:37 PM(UTC)
george.henne

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Recently, my dryer stopped working. It would start fine, run for a few minutes, and then stop. Once stopped, it can't be started up right away. Pushing start will sound the buzzer, but nothing else happens. Changing the position of the dial to different cycles will not change this behavior. After it has had a chance to rest for a while, the process can be repeated.

It will do this in any of the three cycles, including the fluff part of the knit cycle (no heat).

While searching online for help, I found the wiring diagram linked from another post in this forum. With its help, I've tested various parts, both when 'ready' (ready to start) and when 'overworked' (refuses to start).

I've check the resistance across the control thermostat, high limit thermostat, and the thermal limiter. The reading are the same when 'ready' and when 'overworked', with resistants at about 0.5 ohms, except for the part of the control thermostat that reads 28k ohms.

I've been able to get it in an 'overworked' state, cut the power, pull the clips, get the reading, reassemble, re-power and confirm that it is still in it's 'overworked' state. This assures me that it didn't become 'ready' during my tests.

While running, everything seems to be working normally. Heat cycles on and off normally. I've stripped out the drum and door (wiring the door switch closed) and have been able to watch it run. Blower blows. Coil cycles between glowing and not. It didn't get 'overworked' while in this state, but I may not have run it open long enough to test.

I think my tests have eliminated the thermostats and I'm inclined to suspect the motor. I've tested the connections of the motor when 'ready', with the results being open connections, with the exception of the M4 to M5 (as per the wiring diagram) being closed. This makes sense to me given my limited understanding of the diagram.

However, when I tried to test it in an 'overworked' state, I got the same results and, upon reassembly, it was back to it's 'ready' state. This makes the results of the test suspect, as I could have been testing a motor that was again 'ready'. Either way, I think the results would be the same as long as the motor is not actually running (which would make testing rather hard).

I haven't tested the timer yet. My main suspect is still the motor and I'd like to pursue further testing on it.

So, my questions would be:

Any thoughts on what could be wrong?

How can I test if the motor is the cause of failure?

Other than the timer, which I will eventually get to if I can't pin the problem on the motor, is there anything else I could be testing?

And, for anyone who understand the wiring diagram, what is the function of the connection between the high limit thermostat and connection R of the timer? I have a general understanding of most of the paths shown. I just don't understand that one.

Anyway, thanks for any help anyone could provide. I welcome any corrections or critiques. I have a rather basic understanding of these things and I'm trying to learn what I can to be able to deal with such problems as they arise.
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denman  
#2 Posted : Monday, January 31, 2011 2:33:24 AM(UTC)
denman

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Here are your parts
Replacement parts for FRIGIDAIRE MDE336REW0 Kel(v12) / Electric Dryer | AppliancePartsPros.com

[COLOR="DarkRed"]Any thoughts on what could be wrong?[/COLOR]
Sounds like the motor.
What is happening is that the motor is overheating, it then trips it's internal thermal protect. You then have to wait for the motor to cool down so the thermal protect will reset.
[COLOR="DarkRed"]
How can I test if the motor is the cause of failure?[/COLOR]
Try turning the drum by hand in the correct direction. It should turn fairly easily.
You may want to try this on a couple other dryers to get a feel for it.
I would also check the power as low voltage can cause motor's to overheat, this is a bit of a long shot.
If it turns OK then I would replace the motor.
[COLOR="DarkRed"]
Other than the timer, which I will eventually get to if I can't pin the problem on the motor, is there anything else I could be testing?[/COLOR]
The thermostats cannot cause this problem.
The only way a timer could cause it is if a set of contacts were so pitted that they were dropping a fair amount of voltage across them and they would probably burn up or fuse in a very short time.
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george.henne  
#3 Posted : Sunday, February 6, 2011 10:47:00 AM(UTC)
george.henne

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I think you helped pin down the problem. The drum is relatively hard to turn. Removing the belt from the tensioner doesn't make it any easier, so the motor itself probably isn't the problem. I think the problem is the interface between the front panel and drum.

The plastic glides that the drum rotates on were worn so thin that its pretty much riding on the felt. When poking around the glides, one snapped off. I got a replacement and installed it. Unfortunately, it is still hard to turn.

I cleaned up the back part, where the ball rides in the u-shaped socket, and tightened the screws holding the socket in place. However, that part, when turning the drum while holding up the front end, seems pretty smooth. I think the problem is still with the front panel and drum.

I'm thinking that maybe the drum is just so worn that it doesn't slide over the plastic/felt as smoothly as it should. The ring that I imagine was once covered in the same glossy white enamel as the rest of the drum is now worn down to black metal.

Is there anything I could do to help this metal/felt interface move more smoothly? If it was just metal/plastic, I'd try applying some grease. However, I suspect that would be bad for the felt.

If the drum needs replacing, I'd probably just end up buying a new dryer. :(
denman  
#4 Posted : Sunday, February 6, 2011 11:20:22 AM(UTC)
denman

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You did not mention it, did you lube the rear bearing with some high temp grease?

Not a good idea to grease the front as it will eventually work it's way into the drum also it will hold lint.
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george.henne  
#5 Posted : Monday, February 21, 2011 1:07:39 AM(UTC)
george.henne

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Well, I just wanted to provide a follow up.

As far as greasing the rear axle, I put a little bit of some red wheel bearing grease on it. I wasn't sure if it needed it or not, but I figured that it wouldn't hurt.

I endeavored to remove the motor, to see about cleaning it up. After removing some manner of metal clasp and disconnecting the wiring, I was able to get the motor to turn freely in place and was able to determine that it had a lot of lint built up in it. After all the other work, I was able to get it to run for about 10 minutes before overheating, so the hope was to improve air circulation to hopefully fix it.

However, removing the motor completely was a problem. I could identify where it attached to the blower assembly and in the center of the assembly, there is a 7/8 inch hex end. So, I figured it could be twisted off, as this was the last thing preventing me from getting the motor out. Twisting the blower part caused the whole axle to turn. I couldn't find a spot where I could get a good grip on the axle, to facilitate the removal of the blower assembly....

.... I did however find that part of the motor is a somewhat brittle piece of plastic that wasn't up to being clamped by pliers. So, now I have a motor that has a broken part that I doubt I would be able to obtain without getting a new motor. And I now also have a replacement dryer that is installed and working just great.

Ah well. I also learned something else about my setup when I was hooking up the old dryer for the last time. When replacing the connectors on the door switch, I got a spark. I checked the breaker, it was off. (I'll get back to the breaker in a moment) I checked the voltage across the leads for the door switch.... 120v. I checked the unmarked breaker beneath the dryer breaker. I should have realized that there would be two breakers, although I would have expected them to be bound together into a single switch.

Anyway, thanks for the help. It's been a learning experience.
denman  
#6 Posted : Monday, February 21, 2011 3:34:24 AM(UTC)
denman

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Sorry to hear that it did not work out for you.

Oh well as you say "Live and Learn".
The next one you have to work on should be easier now that you have some experience.

At least you did find a dangerous wiring situation without getting hurt.

As you said, the two breakers should be tied together.
Since they are separate breakers there is usually a small metal shaft/tube that ties the two switches together. This of course only works if they are one on top of the other.
If the switches have holes in them perhaps a zip tie will do.
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