Unfortunately, a relative's GE dryer stopped heating, though it was still spinning and everything else seemed to work. There was just no heat on any of the settings. Since I'm the guy in the family with a multimeter, and a pretty extensive vocabulary of curse words, it fell upon me to look at it. I am by no means an expert or electrician, unless getting electrocuted a couple times counts for work experience. So I have to say that this is not a how-to or guide. I do not recommend trying anything like what I will describe here, unless you know what you are doing (and if you know what you are doing you probably wouldn't want to lol). Regardless, working on appliances is it is at your own risk, and there could be errors here in my understanding or recollection of how I worked through this problem - but I will do my best. Hiring a pro to fix the dryer would have been the smart route, though my family is more known for being "frugal" than smart. If you do try and work on one of these dryers though, I suggest wearing some gloves, there are way too damn many sharp edges inside these things.
Once I confirmed that there was no heat on any setting, and checked the outlet for 240VAC. I unplugged the dryer and pulled the front, top and drum off the dryer. Fortunately, behind the mainboard there was a crude schematic with some helpful troubleshooting steps. I would not even write this up, if the basic steps mentioned on the doc had worked, and really they probably would have if I did not really want to be extra special sure of the problem before ordering a part.
Once I confirmed that there was no heat on any setting, and checked the outlet for 240VAC. I unplugged the dryer and pulled the front, top and drum off the dryer. Fortunately, behind the mainboard there was a crude schematic with some helpful troubleshooting steps. I would not even write this up, if the basic steps mentioned on the doc had worked, and really they probably would have if I did not really want to be extra special sure of the problem before ordering a part.
Since the issue was with the heater, I first checked the resistance across both the inner and outer coils of the heater (with no power connected of course). According to the doc, it said those should measure 19.2ohms, and I was getting about that, so the heater seemed OK.
I then took a closer look at the schematic and noted that the mainboard runs off the L1 side, and the L2 side (to boost the heater to 240VAC) is connected only to the output side of the heater coil, which runs through a centrifugal switch attached to the motor shaft. So 90% of the fun happens on the L1 side, which includes the (dumb) thermostats, the biased thermostats and of course the main board. I believe that the dumb (2 wire) thermostats are a safety feature designed to trip and cut power if they sense unsafe temps. This can occur if lint builds up in the air intake from the dryer drum, or there is some other problem related to excessive heating. I believe the "biased" thermostats are also used to regulate the temp of the dryer by cutting off the heating coils when the dryer has reached it's set temp, and then allowing the coils to come back one at a lower temp, to heat back up during a drying cycle. One of the biased thermostats is on the intake for the exhaust duct from the dryer drum, and it can also be affected by lint build up in the front panel ductwork. That is just my assumption based on what makes sense though.
I found a bit of lint in the front ductwork so cleaned that out, but it was not the issue. Since the dryer was apart, it was a good time to clean all the old lint out, and I even found some in the back of the drum behind the heat shield, which I spent about 10 minutes vacuuming out. Side note, the Kobalt portable vacuum is a really handy battery powered wet/dry vac for stuff like this. It has more power than my cordless Dyson by a mile.
So back to the fun. I then went through and checked each of the "dumb" safety thermostats, which have 2 wires, and are located on each side of the top of the heater housing (circled in green and aqua blue in the image below). At room temp, according to the doc I found, these should conduct normally, so I measured them for continuity and also for resistance - they seemed OK. I don't think it is necessary in this case, but one leg of the thermostat could be disconnected to be really sure of the readings. All testing was done with no power connected.
Next I checked the two biased thermostats. These are like the dumb thermostats, but have an additional 2 wires which (as far as I understand it), serve to heat a resistance wire that warms up and "biases" the thermostat. The resistance wire has a resistance of 9KOhms according to the doc sheet. I think the point of using biased thermistors is to allow for some adjustment of the trigger point for the thermostat (and use them a bit like a switch). Not important to the problem with this dryer, but the wires connected to the "bias" elements (9k resistors) on these biased thermostats, are individually controlled by relays on the board. One of these biased thermostats is located on the top left of the heater housing (circled in pink and a bit off the image). This one is in series with the blue (outer coil) wire going to the heater, at the bottom left of the image below (circled in dark blue). The other biased thermostat is located on the front blower intake from the drum (via the front door panel), and pictured with the readings I tested (center pic below). To test these biased thermostats, one side of each connection needs to be removed (or both can be removed). All testing was done with no power connected. They both tested OK.
I then took a closer look at the schematic and noted that the mainboard runs off the L1 side, and the L2 side (to boost the heater to 240VAC) is connected only to the output side of the heater coil, which runs through a centrifugal switch attached to the motor shaft. So 90% of the fun happens on the L1 side, which includes the (dumb) thermostats, the biased thermostats and of course the main board. I believe that the dumb (2 wire) thermostats are a safety feature designed to trip and cut power if they sense unsafe temps. This can occur if lint builds up in the air intake from the dryer drum, or there is some other problem related to excessive heating. I believe the "biased" thermostats are also used to regulate the temp of the dryer by cutting off the heating coils when the dryer has reached it's set temp, and then allowing the coils to come back one at a lower temp, to heat back up during a drying cycle. One of the biased thermostats is on the intake for the exhaust duct from the dryer drum, and it can also be affected by lint build up in the front panel ductwork. That is just my assumption based on what makes sense though.
I found a bit of lint in the front ductwork so cleaned that out, but it was not the issue. Since the dryer was apart, it was a good time to clean all the old lint out, and I even found some in the back of the drum behind the heat shield, which I spent about 10 minutes vacuuming out. Side note, the Kobalt portable vacuum is a really handy battery powered wet/dry vac for stuff like this. It has more power than my cordless Dyson by a mile.
So back to the fun. I then went through and checked each of the "dumb" safety thermostats, which have 2 wires, and are located on each side of the top of the heater housing (circled in green and aqua blue in the image below). At room temp, according to the doc I found, these should conduct normally, so I measured them for continuity and also for resistance - they seemed OK. I don't think it is necessary in this case, but one leg of the thermostat could be disconnected to be really sure of the readings. All testing was done with no power connected.
Next I checked the two biased thermostats. These are like the dumb thermostats, but have an additional 2 wires which (as far as I understand it), serve to heat a resistance wire that warms up and "biases" the thermostat. The resistance wire has a resistance of 9KOhms according to the doc sheet. I think the point of using biased thermistors is to allow for some adjustment of the trigger point for the thermostat (and use them a bit like a switch). Not important to the problem with this dryer, but the wires connected to the "bias" elements (9k resistors) on these biased thermostats, are individually controlled by relays on the board. One of these biased thermostats is located on the top left of the heater housing (circled in pink and a bit off the image). This one is in series with the blue (outer coil) wire going to the heater, at the bottom left of the image below (circled in dark blue). The other biased thermostat is located on the front blower intake from the drum (via the front door panel), and pictured with the readings I tested (center pic below). To test these biased thermostats, one side of each connection needs to be removed (or both can be removed). All testing was done with no power connected. They both tested OK.
So, the coil has the correct resistance (about 20 Ohms on the outer and inner coils), and the thermostats tested OK.
There are a few more switches to check from here though. The first is a switch on the drum pully tensioner. It is located on the left side of the dryer, near the floor pan along the side of the motor. It just closes when the tensioner pulley is tensioning the belt. Since the drum is off, and the tensioner switch is open, I just moved the tensioner pulley to actuate the switch and checked it with my meter (resistance was good). Sorry no pics of that switch. It should be easy to check though, since it makes a nice click when it is actuated.
Recall that most of the fun happens on the L1 side (which powers the board). But the L2 side does have a switch in series that needs to be checked. It is a centrifugal switch attached to the motor, and it is the final say on if the heater is allowed to turn on or not. In the schematic, this is drawn as if it is a separate switch from the rest of the motor switches, but the dashed line indicates it is a "ganged" switch. That means it is part of the switches within the centrifugal motor switch, and is thrown along with another switch (at the same time). This switch was tested without power (everything unplugged). The switch was manually operated by pushing a brown plastic disc which goes around the front of the motor shaft, back towards the coils of the motor (see the first pic below). When activated, the centrifugal switch connects the purple wire (circled in dark purple in the main image of the heater above), with the black L2 line going back to the wall power inlet. This is a bit tricky to access, so I tested the continuity of the switch and it's resistance by removing the plug to the motor and clipping test leads from my meter to the prongs on the motor, which corresponded with the purple and black wires which the centrifugal switch, switches. The images are messy, but space was tight. The center pic below shows how I connected my test leads to the prongs on the motor switch.
As a side note, it is also possible to test this centrifugal switch by connecting a test lead to the L2 side of the power inlet, and the other where the purple wire connects to the lower left side terminal of the heater coils - again with all power disconnected. I tried that as well, but it takes some long leads to reach everything testing that way. The switch still has to be manually activated to test, since it normally only triggers when the motor is spinning at normal speed.
I was happy to find that the centrifugal switch was not the problem, since replacing it appears to require swapping the whole motor. Things were looking more and more like it has to be the board.
There are a few more switches to check from here though. The first is a switch on the drum pully tensioner. It is located on the left side of the dryer, near the floor pan along the side of the motor. It just closes when the tensioner pulley is tensioning the belt. Since the drum is off, and the tensioner switch is open, I just moved the tensioner pulley to actuate the switch and checked it with my meter (resistance was good). Sorry no pics of that switch. It should be easy to check though, since it makes a nice click when it is actuated.
Recall that most of the fun happens on the L1 side (which powers the board). But the L2 side does have a switch in series that needs to be checked. It is a centrifugal switch attached to the motor, and it is the final say on if the heater is allowed to turn on or not. In the schematic, this is drawn as if it is a separate switch from the rest of the motor switches, but the dashed line indicates it is a "ganged" switch. That means it is part of the switches within the centrifugal motor switch, and is thrown along with another switch (at the same time). This switch was tested without power (everything unplugged). The switch was manually operated by pushing a brown plastic disc which goes around the front of the motor shaft, back towards the coils of the motor (see the first pic below). When activated, the centrifugal switch connects the purple wire (circled in dark purple in the main image of the heater above), with the black L2 line going back to the wall power inlet. This is a bit tricky to access, so I tested the continuity of the switch and it's resistance by removing the plug to the motor and clipping test leads from my meter to the prongs on the motor, which corresponded with the purple and black wires which the centrifugal switch, switches. The images are messy, but space was tight. The center pic below shows how I connected my test leads to the prongs on the motor switch.
As a side note, it is also possible to test this centrifugal switch by connecting a test lead to the L2 side of the power inlet, and the other where the purple wire connects to the lower left side terminal of the heater coils - again with all power disconnected. I tried that as well, but it takes some long leads to reach everything testing that way. The switch still has to be manually activated to test, since it normally only triggers when the motor is spinning at normal speed.
I was happy to find that the centrifugal switch was not the problem, since replacing it appears to require swapping the whole motor. Things were looking more and more like it has to be the board.
So with that foreshadowing out of the way, the next thing I checked is the board, which is where things get a bit tricky. In hindsight, I could have just stopped here and tried a new board. However all the stuff I'm posting here is just the highlights of several long hours of investigating the problem, punctuated by swapping meters, test leads, some sacrificial bloodletting, searching for a pair of gloves, and a good deal of cursing. In any case, I decided that I would just do it live. Just like I don't recommend anything from Billy-O, I don't recommend live testing either, and it is of course something that one has to understand and accept the risks of doing. I won't go into full details of what I tested here, since I again do not recommend it, but I first measured AC voltage across the heater coil with it connected (and on), and I was seeing almost no voltage drop (makes sense as it is not heating). I then tested each side of the heater coil to ground and found about 120VAC on each side. Turns out this was mostly coming from the purple wire (L2) side of the 240VAC wall power - and not the board side.
Of course I didn't get pics, but the smoking gun that the problem was the main board, was found when (with all power disconnected) I removed all the wires from the heater coil (the blue and gray on the lower left, and the purple on the lower right). I then covered all the exposed wire connectors with black electrical tape and secured them where possible so they would not flap around. Then I clipped one of my insulated test leads to the purple wire (without the coil connected), and the other lead to ground. After checking things a few times, and with my meter set to measure AC voltage, I plugged in the dryer and turned on the heater. Once the motor spun up and the centrifugal switch clicked over, I measured the voltage drop to ground between the purple (L2 side wire) to ground - it was close to 120VAC. I powered everything off, unplugged and reset to test between the blue (L1 side wire back to the mainboard) and ground. When I plugged in and powered on the heater, it showed just a few volts (around 12VAC). It should have been measuring around 120VAC there as well (from L1). Since it was not, it indicated that the board is not supplying the full power (120VAC) to the L1 side of the heater coil (via the blue or gray wires on the lower left side of the coils). I then powered off the dryer and unplugged it, reconnected the coil wires, and waited a week for a new board, which I found on ebay for $20.
The board swap went well, but the connectors are really tough to remove (yet oddly easy to install). I suspect the problem with my board was a component called an NTC (negative temperature coefficient). My understanding is that these small disk shaped parts with 2 wires are used to limit inrush current. They are not typically used on a resistive load, but I guess they must help even in this case. To test that theory however, I would need to remove the old NTC from the board and test it by trying to heat it up and measure the resistance. For now I will just leave it as my suspicion, since I tested that the relays were working, and there is not much else in series with the heating coils that could cause a limitation on voltage or current.
Below are some pics from the board swap. I labeled each wire, since some of the wires are very close in color and easy to mix up. There are black, brown and black with white stripe wires, and they all get confusing without labels. There is also a plug on the board for "feature select" (see the green arrow below), and that needs to be moved from the old to new board. Finally, before connecting anything to the new board, I checked that the "normal/flash" switch on the left side (right side of the pic) was set to "normal" (circled in red below). I don't know what would happen if it were powered up with that switch in the "flash" position, but I'm guessing it could be bad (may wipe the program for the MCU on the board).
The board swap went well, but the connectors are really tough to remove (yet oddly easy to install). I suspect the problem with my board was a component called an NTC (negative temperature coefficient). My understanding is that these small disk shaped parts with 2 wires are used to limit inrush current. They are not typically used on a resistive load, but I guess they must help even in this case. To test that theory however, I would need to remove the old NTC from the board and test it by trying to heat it up and measure the resistance. For now I will just leave it as my suspicion, since I tested that the relays were working, and there is not much else in series with the heating coils that could cause a limitation on voltage or current.
Below are some pics from the board swap. I labeled each wire, since some of the wires are very close in color and easy to mix up. There are black, brown and black with white stripe wires, and they all get confusing without labels. There is also a plug on the board for "feature select" (see the green arrow below), and that needs to be moved from the old to new board. Finally, before connecting anything to the new board, I checked that the "normal/flash" switch on the left side (right side of the pic) was set to "normal" (circled in red below). I don't know what would happen if it were powered up with that switch in the "flash" position, but I'm guessing it could be bad (may wipe the program for the MCU on the board).
Of course, even after getting it running again, that could not just be the end of the job. While I was taking apart the dryer, I found that the front plastic bearing pads (and some of the plastic molding which holds them) was worn through. This was causing squeaking. I ordered a kit with genuine GE parts, including the front cover, the bearing pads (4), a new felt strip which is also a bit of a bearing for the lower part of the front of the drum, and a new rubber drive belt. It was a pretty decent deal for around $27 to keep it running without squeaking, and was simple to swap. The only question I had when installing it was the orientation of the plastic bearing pads. They provide 2 clear pads and 2 dark gray pads. From what I had seen online, the gray ones go on top, with the plastic ones to the side. The new felt liner goes around the outside of the lower front panel drum guide, and just sort'a rolls into place, with the excess material wrapped around the edge and folded down.
While working on the door, I also noticed that one of the door connectors had come unplugged (circled in green).
After that it was just putting humpty dryer back together again, which was a bit of a pain. The drum is hard to get aligned since the center bearing pin has to be inserted blind. It can help to remove the screws between the sides and the lower frame so the sides can be flexed out just a bit when installing the drum. Just don't forget to put them back like I did lol. The other issue is the belt, which for some reason kept rolling and getting twisted when I tried to reset the idler pulley, but after the third try I got it together without a twist.
While working on the door, I also noticed that one of the door connectors had come unplugged (circled in green).
After that it was just putting humpty dryer back together again, which was a bit of a pain. The drum is hard to get aligned since the center bearing pin has to be inserted blind. It can help to remove the screws between the sides and the lower frame so the sides can be flexed out just a bit when installing the drum. Just don't forget to put them back like I did lol. The other issue is the belt, which for some reason kept rolling and getting twisted when I tried to reset the idler pulley, but after the third try I got it together without a twist.
I hope it's done for now. I noted that there is a rubbing sound, which I think is from the new felt liner, and may take some time to seat in and quiet down, but no squeaking. And most importantly it heats up. It has not been run through a full cycle of laundry yet though, so if it has more problems I will update here.
Update 7/3/2025: So far, so good. There appears to be a slightly different wrinkle guard program on the new board however, since it runs for less time than the old one, but other than that it is working OK (so far). There is an "option plug" which was moved from the old to the new board, which tells the board which model it is working with, so it seems the change is just a difference in the firmware. The board is the identical model number as the older one.
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