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Liko81  
#1 Posted : Tuesday, September 2, 2014 4:23:51 PM(UTC)
Liko81

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Joined: 9/2/2014(UTC)
Posts: 3

Bought a used Maytag Neptune W/D set from a repair/rebuild shop. They live in our garage in the DFW area. The first summer, the thermal fuse on the blower housing tripped; I replaced it, vacuumed out the internal ducting, and told my wife not to run it on its highest setting during the summer months. It's worked fine from then until today, when apparently the same thing just happened again, this time with the heat set to the second lowest setting. I still have to verify it's the fuse, but it's all the same symptoms (control board lights up and responds to input properly, but won't start the drum turning when the Start button is pressed).

I have many questions:

1. There are two seemingly-interchangeable parts for the blower housing thermal fuse: #33001762, and #3392519. The first one is significantly more expensive than I remember paying for the last one. The second one is about what I paid for the last one, but is specifically titled "Non-resettable". Does that mean the first one will reset itself after an overload?

2. I've noticed that on virtually any cycle, even air fluff, the dryer still heats up. Perhaps this indicates a failure in the thermistor/thermostat on either the blower housing or the heater element itself?
* How would I check?
* Say the parts on the blower side indicated a failure; would I need both #307208 and #33002567, or does the thermostat assembly contain the thermistor?

3. I recently ran a new dryer duct through the garage, because the one originally installed in the house is a 3" line that doesn't vent outdoors. The new one is 4" round rigid duct, properly assembled (male end inserts in the direction of airflow) with HVAC tape on all seams, in a run that goes up along one rear corner of the garage where the dryer is, then across the ceiling to the nearest wall, with an S-curve to position it around a wall stud in the exterior wall, and terminating on the other side of that wall in a louvered vent cap. The length, about 25' total, is a bit long for IRC: they specify a maximum 25' for a completely straight vent, minus 5' for each 90* elbow, and so with my 3 elbows they say the vent shouldn't be longer than 10', but that's impossible to accomplish in my space even if I vented it through the roof of the garage. Maytag says their MDE dryers can be run on a vent with 3 elbows up to 36' long, as long as the vent is rigid metal and the vent cap is louvered (check and check), so I'm fine by the manufacturer's specs. In any case it seemed to be working beautifully, airflow was really good, and the vent's been in place less than 3 months so I wouldn't expect there to be any significant lint buildup. Is there anything else I should look out for as far as things I may have done incorrectly that could cause a trip?

UPDATE:

Upon getting home, I tried starting it, and the drum didn't turn, but the heater did start warming up as evidenced by the smell of singed lint. So, probably not the thermal fuse. The motor and drum spin freely, so I don't think it would be the motor, but I did just have to replace the one in the washer (which had frozen completely, wouldn't turn at all).

So at this point I don't know what it could be. I really hope it isn't either the control board or motor; if it is, it isn't worth fixing, the pair cost less than a motor would.
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denman  
#2 Posted : Thursday, September 4, 2014 1:07:18 AM(UTC)
denman

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Here are your parts includes a wiring diagram.
Parts for Maytag MDE5500AYW Dryer - AppliancePartsPros.com
If you click on a part's description or picture a new page will open with more info about that part.

Here is a manual. You will have to join the site and be logged in to be able to download the manual.
http://appliancejunk.com...e&id=67;t=1409823091

You have to be careful that you rare looking at the correct info for your unit as the manual covers many different units.

[COLOR="Blue"]1. Does that mean the first one will reset itself after an overload?[/COLOR]
No, they are the same type of device. Once blown they stay blown.
The 3300172 is the one listed for your unit.

[COLOR="Blue"]2. I've noticed that on virtually any cycle, even air fluff, the dryer still heats up. Perhaps this indicates a failure in the thermistor/thermostat on either the blower housing or the heater element itself?
* How would I check?[/COLOR]
The thermostat is probably OK as you do get heat.
The thermistor should be about 10,000 ohms at room temperature (~70 degrees F)
I do not think either of the above is your problem.
I would start by checking the heater.
Unplug the unit and both wires at the heater.
Measure across the heater should be in the 8 to 12 ohm range.
Now measure from each side of the heater to it's case, both should be infinite ohms.
If not the heater is grounded and should be replaced.
This can cause it to run unregulated.

[COLOR="Blue"]* Say the parts on the blower side indicated a failure; would I need both #307208 and #33002567, or does the thermostat assembly contain the thermistor?[/COLOR]
No
A thermostat and a thermistor are different types of devices.
A thermostat is a set of contacts that open at a certain temperature. They then close again when the temperature drops about 20 degrees F.
A thermistor is a resistor that changes resistance as the temperature changes. This resistance is fed to an electronic board and is used by the board to regulate the temperature (basically the same as an oven probe)

3. Is there anything else I should look out for as far as things I may have done incorrectly that could cause a trip?
Start with the heater.
I cannot comment about the vent. I would suggest you check the air flow at the back of the unit with the vent off and then at the outside louver to see how much air flow you are loosing.
Also be sure to clean/check the vent system every year or so. The S will have a tendency to collect lint.

UPDATE:

Upon getting home, I tried starting it, and the drum didn't turn, but the heater did start warming up as evidenced by the smell of singed lint. So, probably not the thermal fuse. The motor and drum spin freely, so I don't think it would be the motor, but I did just have to replace the one in the washer (which had frozen completely, wouldn't turn at all).

If you do not own a meter, I would suggest you purchase a one. You can get a decent digital multimeter for under $20.00. You do not need fancy though it is nice if the leads are a couple feet long.
If it saves ordering one unnecessary part it has paid for itself and you end up owning a useful tool.
Most places will not let you return electrical parts so if you order it, you own it.
A couple things to watch when measuring ohms and continuity
1. Always remove power from the machine otherwise you could blow your meter.
2. Always disconnect at least one side of any device you are checking. This eliminates the possibility of measuring an alternate/parallel circuit path.
3. When checking for closed contacts and continuity use the lowest scale (Usually 200 ohms). Then try higher scales. This scale is 0 to 200 ohms so if the device you are measuring is 300 ohms this scale would show an open circuit which it is not, you are just measuring outside the scale's dynamic range.
4. When you start always short the meter leads together. This will tell you that the meter is working and if there is any 0 offset.

There is a good STICKY at the start of this forum about it's use.
THIS FORUM IS DEAD!!!!!!!
Liko81  
#3 Posted : Tuesday, September 9, 2014 7:45:58 AM(UTC)
Liko81

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Joined: 9/2/2014(UTC)
Posts: 3

Hi denman,

Thanks for the reply. I do have a multimeter and know how to use it; I also do work on electric guitars and other audio equipment, and have done some home wiring as well, so checking resistance/continuity is old hat.

You pinned it; the heater is shorted to ground on one side. As installed and viewed from the front, the contact on the left side is continuous with the heater shell, so the other contact reads 10 ohms to the shell. These measurements were done with only the front panel removed; to visually inspect the insulator on that side I'll have to do a more complete teardown (nothing I haven't done before; the first time the fuse went I tested the motor to make sure it really was just a fuse).

It seems somewhat odd that a short-circuit at that point would cause the heater to be always on; the thermostat's on the other lead, so I'd expect that to be the "hot" side of the circuit and all the switching should be done on that side (or use double-pole switching). The grounded connector would then be the neutral, undriven side of the circuit, and even with voltage from the other 110V hot lead on neutral, if the control board didn't want the heater on it would cut the circuit on the hot side and the voltage on the neutral couldn't flow through the coil. But, I bet there's much more to the circuit design than I know.

Anyway, assuming that's the only grounded point of the heater circuit, this should be a $4 fix, replacing the insulator on that side instead of the entire assembly. I'll remove the heater tonight and do a more thorough inspection of it to be sure that'll do the job.
Liko81  
#4 Posted : Wednesday, October 1, 2014 1:02:43 PM(UTC)
Liko81

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As an epitaph to this, I tore down the dryer again and took out the heater assembly. The insulators were in fine shape, however the heater coil itself had sagged over time with the high temperatures, until the coil contacted the coil housing, causing the short. Other than that, the coil was continuous and within spec, so I just bent the coil back up into place on the mounting, making sure no other shorts were present between coils, and reassembled the dryer. Been working fine ever since, and effectively a $0 repair (not counting the fuse I already replaced).
Larry75243  
#5 Posted : Tuesday, October 21, 2014 6:35:55 PM(UTC)
Larry75243

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Joined: 9/16/2013(UTC)
Posts: 12

Some of the MOST common reasons for dryer the thermal fuses or other heat sensitive parts is lack of proper air flow.

1. Take the lint screen out. Using a soft brush or even soft rag, use Dawn or some other grease cutting dish soap and clean both sides thoroughly. Use the sprayer on your sink to rinse it out. After time, this lint screen get clogged and it is hard to notice and if anyone is using those dryer sheets, I suggest cleaning it at least twice a year.

2. proper ventilation of a dryer is critical. Whatever hose you use, CUT IT TO SIZE. Extra hose leads to potential air flow reduction and that means it it will take longer to dry which means it is heating the element longer than it should. I have elements laying around here from 30 year old appliances that look like new other than age and none have sagging coils in the element. That scream it is running too long without proper air flow.

3. While the dryer is away from the wall, get your leaf blower and shove it into the hose or vent heading outside. Turn it on the highest speed possibly and have someone outside see how much crap comes out.
(you may have had rodents or birds build nests in there blocking the vent and loving the warmth but a good leaf blower works like a champ to clear that out!

4. Speaking of outside. Make sure that if there is a cover over the vent outside it is not filled or clogged. Another oft overlooked maintenance item. The one on the side of my house tends to need cleaning a couple times a year depending on how many loads I do.

These are basic cleaning tips very few people ever bother with when they have discovered a thermal fuse failed.
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