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-   -   Maytag electric dryer won't heat (http://forum.appliancepartspros.com/dryer-repair/517374-maytag-electric-dryer-wont-heat.html)

kspeters 02-06-2013 06:23 PM

Maytag electric dryer won't heat
 
Dryer won't heat. I have checked continuity on the parts on the heat assembly tube. All checked good. When running I have 120 on either side of heating element but when i put the blacklead on one side and the red lead on the other side I read a couple volts, not 240. The fuses test good with continuity and the machine operates fine but just does not heat. I even put a wet rag on the moisture sensoe so it reads wet, still no go. Any ideas?

denman 02-07-2013 02:08 AM

Sounds like a power problem.

Try flipping the breaker off/on slowly a couple times, sometimes you can loose half the line without actually tripping the breaker.
If this does nothing, check the voltage at the plug
L1 to L2 should be 240 volts
L1 to Neutral and L2 to Neutral, both should be 120 volts.
If OK
Unplug the unit and check the wires at the terminal strip in the machine to make sure none are loose or burned out
If OK
Check the power at the terminal strip.
Be careful as 240 volts is lethal !!!

kspeters 02-07-2013 05:29 AM

Thanks for the reply. Yeah I checked my power already and had 240 at the power junction block on the back of the machine and everything was tight. I was looking at the schematic diagram and I am assuming that the heating element has the two legs of the 240 v connected to it and that I should see 240 volts across the two connectors when running? I do not and actually it reads just a couple volts. When I take one of the wires off the element and test I will see 120 v. Why is that? I have nott ested the switches in the control panel b/c I don't know what to expect from those contacts as far as voltage.

denman 02-07-2013 08:30 AM

I am assuming that the heating element has the two legs of the 240 v connected to it and that I should see 240 volts across the two connectors when running?
That is correct.

I do not and actually it reads just a couple volts. When I take one of the wires off the element and test I will see 120 v. Why is that?
I am not sure what you are doing when you measure the 120 volts.
Is one meter lead on an element connector and the other on the frame/Neutral/ground?
Also was the motor running when you did this?

Using the wiring diagram.
If the motor is running and you are checking from a heater connector to ground you would see 120 volts on the left hand side (BK). The circuit path is L2 , motor's centrifugal switch BU/BK (closed when motor is running) , heater connector.
Now here is where it gets a bit tricky. If the element is good but the other side of the element has an open in the circuit , then you see 120 volts on both sides but it is the L2 voltage on both sides. Neutral is not normally part of the heater circuit so no voltage is dropped across the heater so you see the same volts on both sides.
If the circuit path on the other side of the heating element is good then you will also see 120 volts but it is the L1 voltage so there is 240 across the element and it heats up..

Just in case you do not know how 240 works.
Your power is actually two 120 volt power supplies when referenced to Neutral but they are 180 degrees out of phase. So when one is at positive 120 the other is at negative 120, that is how you get 240 volts. The heater runs between these two supplies (L1 and L2). Neutral is not part of this circuit.

Now for the right hand side of the heater circuit.
BR on the heater , HI-LIMIT thermostat , PU and the contacts of the CYCLING thermostat , red on the TEMP SWITCH , the RD (red) to BU (blue) contacts are closed in any heat mode , BU at TIMER contacts 3 also closed in any heat mode , to the contacts a TIMER contacts 4 also closed, BK (black) to L1.

Now for some testing
With the unit unplugged and the timer set to mid scale of a heating mode.
You should have 0 ohms at all points from L1 to BR on the heater circuit. Use the most sensitive meter scale.
Can also do this with the unit (motor) off but connected to power, then you should see 120 volts at all points.
Using resistance is just a lot safer.

I hope I did a decent job explaining and have not confused you.

kspeters 02-07-2013 04:36 PM

I do not and actually it reads just a couple volts. When I take one of the wires off the element and test I will see 120 v. Why is that?
I am not sure what you are doing when you measure the 120 volts.
Is one meter lead on an element connector and the other on the frame/Neutral/ground?
Also was the motor running when you did this?


Motor running, I had the wires off of the element and checked between the wires and frame.

I did not understand completely on your path on right side.
I just cannot figure out why I don't see 240 when going across the two legs.
Is there anyplace where it wuld tell me the voltages I should see across all contacts when running?

"Now for the right hand side of the heater circuit.
BR on the heater , HI-LIMIT thermostat , PU and the contacts of the CYCLING thermostat , red on the TEMP SWITCH , the RD (red) to BU (blue) contacts are closed in any heat mode , BU at TIMER contacts 3 also closed in any heat mode , to the contacts a TIMER contacts 4 also closed, BK (black) to L1."

Are you saying red from cycling therm to temp switch red to temp switch blue to bu on timer closes to bk to L1 is the path? So L1 is hot all the time and the timer closes to allow voltage flow to BU?

denman 02-08-2013 02:20 AM

Motor running, I had the wires off of the element and checked between the wires and frame.
This is a bit of a puzzle, since the element is not in circuit it cannot conduct the L2 voltage to the right side (BR) of the element.
There is a possibility that you were measuring the L1 voltage on both wires.
It would conduct the right side through the normal heater circuit path. Then depending where your TEMP SWITCH was, it could conduct the same voltage through the CYCLING thermostat's internal heater to the left side BK BK

I did not understand completely on your path on right side.
I just cannot figure out why I don't see 240 when going across the two legs.
Is there anyplace where it wuld tell me the voltages I should see across all contacts when running?

Not that I know of.
Your problem is that using voltage is confusing because you have two 120 volt supplies (L1 and L2) referenced to ground and there is no way of knowing which supply you are measuring unless you have an oscilloscope.
That is why using resistance is a better trouble shooting method for everything except the motor's centrifugal switch.
With the unit unplugged and the timer set to mid scale, timed dry, regular heat. Using the most sensitive meter scale and one lead on L1 and left there.
You should read 0 ohms back through the heater circuit all the way to the right side of the main heater (BR).


Are you saying red from cycling therm to temp switch red to temp switch blue to bu on timer closes to bk to L1 is the path?

Yes.

So L1 is hot all the time and the timer closes to allow voltage flow to BU?
Yes, timer switches 3 and 4 are closed when the heater is supposed to be on.
Then when the motor gets close to operating speed it's centrifugal switches close and L2 is applied to the left hand side of the heating coil.
There is a live test that may help your troubleshooting, hopefully the BK heater and the BK cycling thermostat heater have plugs on both wires so they can be disconnected from each other and the main heating coil.
Then with the motor running you should see 120 volts (main heater's BK wire to ground). This then tell you that the centrifugal switch is closing and that you are getting L2 to the heater.

kspeters 02-09-2013 07:12 PM

I think I found out the switch is bad. Got one on order so hopefuly that does it. Thanks for all the help.

kspeters 02-13-2013 07:36 PM

Quote:

Originally Posted by kspeters (Post 799002)
I think I found out the switch is bad. Got one on order so hopefuly that does it. Thanks for all the help.

It was indeed the timer switch. Thanks for all the help.

denman 02-14-2013 02:43 AM

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.

Telicoman 02-24-2013 09:46 AM

Similar problem
 
I apologize for bumming someone else's thread but I have a maytag mde7600ayw that won't heat like the OP's. I have continuity from the red wire comming in from the back of the unit all the way through to the black wire on the other side of the heating element. I don't have a wiring diagram however, to test the centrifugal switch where do I test? Also to test the timer switch?
Thanks, Mike


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