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Hi all,
Model: Maytag MDG3706AWW
Replacement Timer Part #: AP4047639
Problem:
Dryer does not turn off on certain settings.
Timer works/turns on Timed setting but does not properly work on Auto settings. This is with a new timer from AppliancePros.com.
Tests:
Checked all continuity of the thermostats and all are fine.
Below are test results from the various settings using a multimeter:
Auto Dry Regular Setting...
More Dry - 120v
Normal Dry - 120v
Somewhere between Normal and Cool Down, a click is heard when the timer knob is moved forward - 0v
Cool Down - 120v
Auto Dry Wrinkle Control Setting...
More Dry - 0v
Normal Dry - 0v
Less Dry - 0v
Cool Down - 120v
Timed Dry Setting...
100minutes to Cool Down - 120v
Diagnosis...Received a bad new timer or something else is wrong?
Question for the Pros...
I'm told that the timer motor power lines should always receive 120v when it's engaged. As noted above, at certain points, there is no power going to the motor so it doesn't move which results in the dryer being constantly running. Was I given correct info?
How are the other two knobs (Signal On/Off and Temperature) affect the timer motor, if it's affected by them? Would one or both of those knob settings cause the timer motor to be turned off/on?
Thanks!
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The timer motor only receives power all the time in timed dry mode. In auto dry, the cycling thermostat either provides power to the heater or the timer motor. During the first part of auto dry, the wet clothes absorb most of the heat in the drum and thus not enough heat gets to the blower where the operating thermostat is and it doesn't change position. As the clothes get dry, more heat gets to the operating thermostat which causes it to begin cycling between powering the timer motor and heater. At the end of auto dry, a set of timer contacts closes to provide power to the timer motor all the time regardless of operating thermostat position. Monitor the voltage at the orange wire on the timer to determine if the operating thermostat is cycling. Voltage should switch between 120 and 0. You may have gotten a bad timer but problem could also be the operating thermostat is failing or there is an airflow problem.
Eric
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Thanks Eric.
I'll do as suggested.
I did clear all airflow paths of any lint/debris so airflow should be fine.
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Originally Posted by: fairbank56  Monitor the voltage at the orange wire on the timer to determine if the operating thermostat is cycling. Voltage should switch between 120 and 0. Can you clarify how I should monitor the voltage at the orange wire? Do I just connect the multimeter probes to the orange wire and ground while it's running and wait? From your explanation, since the cycling thermostat needs to be triggered, it appears I would have to wait and watch for any voltage changes as the dryer is working. If so, how long should I sit, watch and wait before I suspect something is wrong? Thanks!
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More observations...
1) the orange wire to the motor has a Y that also goes to the Temperature knob. Not sure if that helps. Since it was easier to access the orange wire connector here, I connected a small alligator clip to it and to a green ground wire. The other ends went to the multimeter.
2) When there is power, 120v, to the motor power cables, the same is true to the orange wire, vice versa.
3) On Auto Dry Regular setting, it heats up ONCE until it goes to that click mark just before the cool down mode. At this point, power to the motor is 0v (it's actually 1.xx volts). Heat no longer goes on even if I stop the dryer and restart it from the beginning of the cycle. Unplug and plug in power cord, same results.
4) On the Auto Dry Wrinkle Control Setting, 120v is shown when I turn the knob when the dryer is not running. The moment I press the knob to turn on the dryer, voltage drops to 0v. As long as I'm not in the Cool Down area, voltage stays 0.
Methinks there's a sensor I missed somewhere. When I opened up the unit, I see what appears to be 2 sensors near the gas flame burner toward the front of the unit. These were the ones I tested and they have continuity. In the back is the heat airflow pathway into the dryer drum. I can't access this from the back of the machine. If there's another sensor back there, I'd have to remove the drum assembly to get to it. Otherwise, am I missing another somewhere else?
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Rank: Advanced Member
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There aren't any sensors in the back of the dryer. The only sensor that controls the timer motor is the operating thermostat located on the front of the blower housing. Does the timer advance on it's own during auto dry cycles? When the burner cycles off in auto dry, the timer should advance until burner lights again. Post a copy of your wiring diagram so I can compare it to the one I have for your model. May be different.
Eric
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Rank: Member
Groups: Registered
Joined: 7/10/2014(UTC)
Posts: 7
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Rank: Advanced Member
Groups: Expert
Joined: 10/16/2012(UTC)
Posts: 3,806
Was thanked: 7 time(s) in 7 post(s)
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Ok, that is the exact same one I have. You didn't answer the question as to whether the timer advances during auto dry. In the end stage of either auto cycle, timer contact 1A should close which applies 120vac continuously to the timer motor which should advance timer to the OFF position and turn the dryer off. If the timer does not get to the end stage of auto cycle, then either the operating thermostat is faulty or there is a heater/air flow problem preventing that thermostat from getting hot enough to cycle.
Eric
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Rank: Member
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Only the Timed and Auto Dry Regular settings advance by itself as noted in the first posting.
I'll open up the dryer again and recheck the continuity of the thermostats again.
Where else can I check for airflow problems? The outside vents gets plenty of exhaust flow. I've completely removed the plastic lint guard and washed it clear of any traces of lint. The airflow channel to the rear is cleared as well. The only section I haven't check is the heat flow channel into the drum from the backside.
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Rank: Member
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Opened the dryer and checked all three thermostats. Sure enough, the one at the exhaust end didn't have continuity. It was also the one where the orange wire was attached to. Let's hope this is the culprit.
Thanks Eric for all your help.
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