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kapnkrunk  
#1 Posted : Tuesday, August 21, 2012 5:23:53 AM(UTC)
kapnkrunk

Rank: Member

Groups: Registered
Joined: 8/21/2012(UTC)
Posts: 1

I have a Maytag Admiral LNC7764A71 that's approximately 10-years old. I've never had an issue in all of this time. This past weekend, in the middle of a laundry load, the dryer just simply STOPPED, and it was accompanied by a stink/burning smell. So, clearly something went bad. The light no longer comes on when you open the door, and the dryer is completely unresponsive in any other way.

I've spent the weekend teaching myself diagnostics (thanks largely to advice on this site), and here's what I've done so far:

1. Tested Hi-Limit Thermostat with a Meter. Tested fine. (ie, registered 0-Infinity OHMS with meter)
2. Tested Door switch with Meter. Tested fine.
3. Tested Outlet with Meter (4 pront outlet). Specifically, tested the two vertical HOT slots and the L-shaped Neutral slot. Tested fine.
4. Tested Power Cord. Specifically, touched Meter to prongs on power cord and corresponding hot/neutral connections on the back of the washing machine (to which the power cord was connected). All connections tested fine.
5. Tested Heating Element with Meter. Registered 10 ohms. Should be fine (yes?).
6. Tested Cycling Thermostat. Tested fine.
7. Noticed LOTS of lint in the vent/blower. Cleaned all of that out and re-secured the vent "tube" in back just to be sure.
8. Cleaned out remaining lint all inside the cabinet.

At this point, I'm not sure where to go. Any suggestions? I've looked at the wiring diagram to find out where to go from here, but I have no idea how to read those things.

Anything else I should test out, or is it time to call the Maytag man?
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denman  
#2 Posted : Wednesday, August 22, 2012 3:10:38 AM(UTC)
denman

Rank: Advanced Member

Groups: Senior Expert
Joined: 2/29/2008(UTC)
Posts: 19,638

Here are your parts, includes a wiring diagram.
Replacement parts for Admiral LNC7764A71 DRYER- ELE | AppliancePartsPros.com
Note: part of the wiring diagram is cut off. What is missing is that the right hand side of the Motor Cent. (centrifugal) Switch is connected to L2.
[COLOR="Blue"]
Anything else I should test out, or is it time to call the Maytag man?[/COLOR]
Not yet.

You did not mention testing the thermal fuse (Item 5 in Section 4).
It kills the neutral to the motor but also is before the light in the circuit so would also kill your drum light.
If it is blown you should find out why,[COLOR="Green"] see below[/COLOR].

Seems you may need a little help with diagnosis or at least the terminology.

[COLOR="Blue"]1. Tested Hi-Limit Thermostat with a Meter. Tested fine. (ie, registered 0-Infinity OHMS with meter)[/COLOR]
0 ohms is a closed circuit. Infinity is an open circuit. So it cannot be both.
[COLOR="Blue"]
3. Tested Outlet with Meter (4 pront outlet). Specifically, tested the two vertical HOT slots and the L-shaped Neutral slot. Tested fine.[/COLOR]
I am assuming this was a voltage check.
Your house electrical is actually two 120 volt power supplies (L1 and L2) which share a common Neutral. They are 180 degrees out of phase. When one is at positive 120 volts the other is at negative 120 volts. This is how you get 240 volts which runs the heater in the unit. The motor, light bulb and timer all run off of 120 volts (:L1 to Neutral)

[COLOR="Blue"]5. Tested Heating Element with Meter. Registered 10 ohms. Should be fine (yes?).[/COLOR]
Yes

Colored pencils can help when trying to follow a circuit diagram.
Just use different colors for L1, L2 and Neutral, it is then easy to follow what circuit runr what devices/parts.

[COLOR="Green"]If the thermal fuse is blown.[/COLOR]
Check the heating coil.
Unplug the unit and both wires to the coil.
Check it with a meter, should be around 10 to 12 ohms.
Then check from each side of the coil to the case/frame, both should be infinite ohms (open). If not the coil may have sagged or broken and is touching the case. This can cause it to run on high and the thermostats cannot regulate it so the thermal cut-off blows.

The hi-limit should have regulated the temperature so the fuse did not blow, that is why there is a new one with the thermal cut-off..
Note: That unless there is another problem in the unit the hi-limit should never have to open. It is just a safety device with the fuse being a backup safety device.

Just in case it is not a grounded element.
With all the below the high limit will also have to be replaced.
Check that the belt is OK.
Check the seals (drum etc) in the unit. The air is pulled over the heating coils, through the drum and pushed out the exhaust. So any large seal leak will pull in room air and the cycling thermostat on the blower will run the unit hot.
Check that the lint filter is not coated with fabric softener residue which greatly reduces air flow.
Check/clean your vent system.
Check/clean the blower wheel.

If all OK you may want to replace the cycling thermostat as it's contacts may not be opening (welded shut)

Just a bit on meter usage.

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 (infinity) 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.
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