How does an electric dryers cycling thermostat work?

Reply

  #1  
Old 06-28-20, 01:36 PM
CircuitBreaker's Avatar
Member
Thread Starter
Join Date: Jan 2009
Location: Trumbull, CT, USA
Posts: 499
Received 11 Votes on 11 Posts
How does an electric dryers cycling thermostat work?

I know a person who has a coin operated Whirlpool (unknown model but its from 2008) and the thermostats two outside terminals have continuity and will cut out when heated (I put it on the burner of my electric stove). The two small inner terminals have no continuity at room temp or heated. So how are they supposed to work? The dryer runs just no heat. Also since it is an electric dryer it should be a 240V part? the part says heater 120V

Thanks

I am just the messenger I am not the one actually fixing the machine a friend of mine is.


 
Sponsored Links
  #2  
Old 06-28-20, 01:43 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 57,102
Received 840 Votes on 787 Posts
That thermostat has a 120v heating element in it. That's the two small leads. There is probably a very high resistance on those terminals. The two larger ones are the actual thermostat. Even without the heating element part working..... the dryer will still make heat.

Your problem is not there.
 
  #3  
Old 06-28-20, 01:51 PM
CircuitBreaker's Avatar
Member
Thread Starter
Join Date: Jan 2009
Location: Trumbull, CT, USA
Posts: 499
Received 11 Votes on 11 Posts
My meter said "OL" when I tried measuring those two small terminals. What is that 120V heaters purpose in the dryers heating circuit?
 
  #4  
Old 06-28-20, 02:53 PM
pugsl's Avatar
Forum Topic Moderator
Join Date: Mar 2008
Location: United States
Posts: 8,886
Received 59 Votes on 55 Posts
The heater in thermostat is what opens it. There is no sensor in dryer to tell thermostat to open for a lower temp. They have added a heater in thermostat to fool it. Heat problems are almost always caused by open heater or open thermostat. Not the temp control one. In many years of dryer repair I have not found one bad. dryer is only 240 at heater element. meter will always show 120 unless you are measuring L1 and L2
Your thermostats and heater should show continuity. If open it is bad.
 
  #5  
Old 06-28-20, 06:19 PM
CircuitBreaker's Avatar
Member
Thread Starter
Join Date: Jan 2009
Location: Trumbull, CT, USA
Posts: 499
Received 11 Votes on 11 Posts
OK I guess the part is good then. Probably a stupid question but if I connect 120V to those center heater terminals how much current should it draw and how hot should it get? Is that even a good idea to test it (I assume not but I'd thought I'd ask before I do that).
 
  #6  
Old 06-29-20, 03:35 AM
pugsl's Avatar
Forum Topic Moderator
Join Date: Mar 2008
Location: United States
Posts: 8,886
Received 59 Votes on 55 Posts
Never tried it. the thermostat is turned on by the low heat switch. Like I said before have never found one bad for no heat. Maybe no low heat setting will still get hot.
 
  #7  
Old 06-29-20, 04:50 AM
M
Member
Join Date: Sep 2019
Location: Canada
Posts: 1,367
Received 135 Votes on 125 Posts
OL on the meter means the internal heater is open.
Does not mean that is bad as it depends on what meter scale you used. The heaters oar usually in the 5,000 to 10,000 ohm range so you have to use the 20K resistance scale on the meter to measure it.

If there is infinite resistance then it is bad.
But will only effect the lower heat settings so the unit would always run on high heat.

The first thing to check in a no heat condition is the power at the terminal strip in the unit.
L1 to Neutral should be 120 volts
L2 to Neutral should be 120 volts
L1 to L2 should be 240 volts.
Just checking each side to the Neutral for 120 volts is not good enough you must check that it gets 240 volts.

 
  #8  
Old 06-29-20, 12:59 PM
CircuitBreaker's Avatar
Member
Thread Starter
Join Date: Jan 2009
Location: Trumbull, CT, USA
Posts: 499
Received 11 Votes on 11 Posts
I have an auto ranging multi-meter Sears/Craftsman model 82139.

Anyway that part is good I tested the heater part by connecting a 120V cord and that part got hot and the thermostat turned off.

I told the friend that is fixing the machine that he needs to check for 240V while the dryer is running, I assume the easiest it to check at the terminal block at the back or is there an easier way? the panel is about 100' away

The NM cable is orange in color and he said the jacket said 10/3 w/GND so that requires a 4-wire 14-30R and the matching 14-30P on the dyers end.

So you measure L1 - L2 and you should get around 240V correct and L1 or L2 - neutral or ground around 120V.

I have a hunch that the 240V is somehow missing.

Can you check those thermal cutouts (those one shot ones) in circuit or do you have to disconnect the wires from it. He tested in in circuit and all of them and the element tested good.
 
  #9  
Old 06-29-20, 01:18 PM
M
Member
Join Date: Sep 2019
Location: Canada
Posts: 1,367
Received 135 Votes on 125 Posts
Terminal block is the best because it tests the line, the receptacle and the cord.

The thermal cut outs etc. can be tested in circuit but you must use resistance and see close to 0 ohms.



 
  #10  
Old 06-29-20, 01:47 PM
CircuitBreaker's Avatar
Member
Thread Starter
Join Date: Jan 2009
Location: Trumbull, CT, USA
Posts: 499
Received 11 Votes on 11 Posts
Yes he said everything passed a continuity test, so I guess the 240V circuit is somehow broken. He was measuring the cycling thermostat the wrong way one end prong to a center but as I found out by searching and this forum that they are separate parts.
 
  #11  
Old 06-29-20, 05:40 PM
M
Member
Join Date: Sep 2019
Location: Canada
Posts: 1,367
Received 135 Votes on 125 Posts
Do you have a model number for this dryer?
It may be possible to find a wiring diagram.

Usually a dryers heater circuits are wired as
L1
A set of timer contacts. This could be more complicated here because it is coin op.
Thermal cut-off
Operating thermostat
Hi-limit thermostat
Heating coil
Centrifugal switch on the motor
L2
 
  #12  
Old 06-29-20, 06:32 PM
CircuitBreaker's Avatar
Member
Thread Starter
Join Date: Jan 2009
Location: Trumbull, CT, USA
Posts: 499
Received 11 Votes on 11 Posts
Sorry I don't have the model number all I know it is a Whirlpool coin operated electric dryer from 2008. I agree a model would be helpful but unfortunately don't have that available yet.
 
  #13  
Old 06-30-20, 03:34 AM
pugsl's Avatar
Forum Topic Moderator
Join Date: Mar 2008
Location: United States
Posts: 8,886
Received 59 Votes on 55 Posts
Back to basic. Does not heat or dose not run. two different things to check. Coin part does not change how dryer works just how it is turned on.
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: