Mle24pdayw1 Coin stacked maytag commercial dryers heat only when both dryers are running

[Ellen Callaway]

I have stacked dryers that only heat when both dryers are in running. We have changed out the control board with a know working one. Same issue. We have ck continuity on the Aa12 connector all is good. We changed out the thermal cutoff, hi limit thermostat and thermal fuse on the top dryer as this is where we first thought we had a problem. Same symptoms still. Can someone please help or point me in the right direction?

[16345Ed]

Makes no sense. Two separate dryers plugged into two separate outlet. How can one effect the other unless outlet wiring us screwed up somehow?

[Budget Appliance Repair]

@16345Ed Not two separate dryers each with own cord - 2 identical units married together with a separator between the two dryers that contains the terminal block and single incoming power cord.

@Ellen Callaway does neither dryer heat when running on there own or does one always work but the other only heats when the one that does work is on?

I don't have a wiring diagram to look at, so don't know how each is attached to power and there is a relay in the separator/control panel area, (this maybe a heater relay).

It sound like there maybe a wiring problem, (maybe in terminal block area), that when the one that works is running it is routing the missing L1 or L2 heater power to the opposing dryer when the one that works is on.

[Ellen Callaway]

Thank you Budget! 
Neither dryer will heat independent of each other. If I turn both dryers on they heat fine. If I turn one dryer off the other dryer starts cooling down while still running. I feel like maybe wiring too but I don’t understand it enough to know where a dryer can  borrow a line to obtain the power it needs heat up. 
 

These are identical with a separator but each dryer does have its own plug in to the wall. 
 

I am trying to send a wiring diagram 

[Budget Appliance Repair]

OK, I see it does show a separate power cord for each dryer but one common control board that controls both dryers.   Since you say you already replaced the board with a known good working board, I still suspect you have a power supply problem or maybe a bad thermal fuse in the lower dryer.

Check to make sure you are getting 240 Vac to both power cord terminal blocks and make sure the transformer that supplies the power for the control board is outputting all the correct low voltages.

Need to find out what side of the heat circuit doesn't have voltage at each dryer when running each on it's own where it isn't heating.  I suspect you will find that the L1 supply of the heating circuit is missing for each dryer when running on there own and not heating.

Each dryer has it's own heater relay that supplies L1-Black to the heating element when the board tells the relay to close.  I don't know what the relay control coil voltage is but suspect it to be either the 20.8Vac or 26Vac that the board would supply to either one or both of the heater relay coils.  Check the voltage at the control coil of each of the heater relays with just that single dryer running without it heating/failing state then check each again with both dryers running.

Has this dryer been in this same location and all same power hookup and working totally fine then at some point the problem of not heating started or has it just recently been installed in this location and hasn't worked?

The heating elements, cycling t-stats, hi-limit safety t-stats and heater thermal cut-offs all have to be OK on both dryers because if any of those where bad you wouldn't be getting any heat at all to the dryer with any of those parts bad.

You say you replaced the thermal fuse on the top dryer but don't mention if you checked the thermal fuse on the lower dryer - from the diagram I don't know if the board supplies L1 voltage to the motors by the LBU - Light Blue wire or the O-BK - Orange-Black wire.

I would need more tech info to see how the motor circuits work as in most electric dryers if the thermal fuse blow it shuts down the motor circuit but it looks like the thermal fuses in this unit are a sense line for the board to know the fuse isn't blown then the board can turn on the heat relays so the motors could still run with a thermal fuse blown unlike in most normal Whirlpool electric dryers.

I guess there's a possibility that L1 & L2 are swapped on one of the dryers and so with a bad thermal fuse with both dryers running your getting feed back voltage somewhere thru the board for it to think the fuse is OK and then lets it heat but seems kind of unlikely from a safety standpoint.

That's all I got for you with just the wiring diagram.

 

[Ellen Callaway]

On 7/14/2022 at 7:29 AM, Budget Appliance Repair said:

OK, I see it does show a separate power cord for each dryer but one common control board that controls both dryers.   Since you say you already replaced the board with a known good working board, I still suspect you have a power supply problem or maybe a bad thermal fuse in the lower dryer.

Check to make sure you are getting 240 Vac to both power cord terminal blocks and make sure the transformer that supplies the power for the control board is outputting all the correct low voltages.

Need to find out what side of the heat circuit doesn't have voltage at each dryer when running each on it's own where it isn't heating.  I suspect you will find that the L1 supply of the heating circuit is missing for each dryer when running on there own and not heating.

Each dryer has it's own heater relay that supplies L1-Black to the heating element when the board tells the relay to close.  I don't know what the relay control coil voltage is but suspect it to be either the 20.8Vac or 26Vac that the board would supply to either one or both of the heater relay coils.  Check the voltage at the control coil of each of the heater relays with just that single dryer running without it heating/failing state then check each again with both dryers running.

Has this dryer been in this same location and all same power hookup and working totally fine then at some point the problem of not heating started or has it just recently been installed in this location and hasn't worked?

The heating elements, cycling t-stats, hi-limit safety t-stats and heater thermal cut-offs all have to be OK on both dryers because if any of those where bad you wouldn't be getting any heat at all to the dryer with any of those parts bad.

You say you replaced the thermal fuse on the top dryer but don't mention if you checked the thermal fuse on the lower dryer - from the diagram I don't know if the board supplies L1 voltage to the motors by the LBU - Light Blue wire or the O-BK - Orange-Black wire.

I would need more tech info to see how the motor circuits work as in most electric dryers if the thermal fuse blow it shuts down the motor circuit but it looks like the thermal fuses in this unit are a sense line for the board to know the fuse isn't blown then the board can turn on the heat relays so the motors could still run with a thermal fuse blown unlike in most normal Whirlpool electric dryers.

I guess there's a possibility that L1 & L2 are swapped on one of the dryers and so with a bad thermal fuse with both dryers running your getting feed back voltage somewhere thru the board for it to think the fuse is OK and then lets it heat but seems kind of unlikely from a safety standpoint.

That's all I got for you with just the wiring diagram.

 

Ok. Thank you so much. We have ck everything we know. What we have found is on Pins 6 &1 we get 1vac where we should  be getting 5.8   On Pin 7 & 4 we get 1 where we should be getting 20.8 on connector AA8 going to the Transformer.  The wire and connector look fine. The plugs into the wall ck fine for voltage. Can it be anything else but a bad transformer?  Thank you 

[Budget Appliance Repair]

From the diagram I see AA8 6-Blue & 2-Blue should be 5.3 Vac, (Not 6 & 1, it and 2 & 1 should be 2.7 Vac), and maybe just a typo on your part but the 20.8 Vac should be on 7-White & 3-White (Not 7 & 4)

If you are getting only 1 Vac and you are getting the correct 26 Vac on 8 & 4 then you would have to be getting the correct 120 Vac to the transformer to get the correct 26 Vac, (you didn't say if you are getting the 26 Vac which should be on 8-Red & 4-Red).

I don't see how if only the 26 Vac output was working correctly that they other voltages would come up with both dryers running but not with only one running, (the transformer is only supplied with it's 120 Vac from one of the power cords - are you getting the correct 120 Vac to the transformer with both dryers off?).

The heater relay coils are rated at 24 Vdc, so I would think the 26 Vac from the transformer would be rectified to DC on the board to supply the heater relays with 24 Vdc.

You still haven't said if these dryers have been working fine in this location and just started having this problem or not?

 

[Ellen Callaway]

I apologize but yes the units have been in place for several years and in fine working order until this incident. 
 

I will reverify the pins. Thank you 
 

 

[Ellen Callaway]

Pin 6 & 2 (blue).  5.0

Pin 2 & 1 ( blue & Yellow)  2.5

Pin 7  & 3 ( white) 22.45

Pin 8 & 4  ( red) 28.00

Above is the actual ck for voltage

we did ck thermal fuse  heating element cycling t stats hi limit safety t stats and heater thermal cut offs for continuity on the bottom dryer  they all seem to be fine. 
 My maintenance guy ck the orange wires going to Pin 1 & 4 in bb2 and orange wires on Aa12 with only one dryer running at a time. He says they are fine. 
 Thank you for all your help. Me and the maintenance man must be overlooking something that you understand and we don’t   

 

[Budget Appliance Repair]

You say you checked the ORANGE wires in BB2 and AA12 and they where OK with only one dryer running at a time - Can you be more specific as to OK - What voltage are you getting to each of those with just each individual dryer on at a time and with both dryers on at same time.

Those are the wires to the coils that should close each heating relay to turn the heat on.

On each dryer with just that dryer running at the time of testing you need to half-split your voltage checking on the heating system and find out which side of the 240 Vac to the heating system that you are not gettng.

If you don't understand what I mean by half-split, it means to remove one of the wires from the heating element itself or at the heating relay would probably be a better place to do this.  Then check the voltage to the removed wire to a Neutral point then again from the Neutral point to the wire that is still attached.   At the relays, if you remove the RED wire from the relay and check from the RED to a Neutral you should get 120 Vac, (if you don't then the something in the main heating circuit - motor switch, thermal cutoff,hi-limit safety t-stat, cycling t-stat or heating element is bad.  Then do the check from the BLACK wire that is still attached to the relay to Neutral, if you don't get 120 Vac here than there is something wrong in the wiring to the relay because the BLACK-LINE1 is feed directly from the terminal block to the relay.

Do you have 3 prong power cords or the 4 prong type?