Samsung dryer overheating, tried some things to no avail!! (1 Viewer)

[alia176]

Hiya fellas,

My GF is at her witt's end with the Samsung dryer showing the HE fault, which is "overheating". The #1 cause of this is the vent that's obstructed, which isn't the case here. I'm going sound out what my thoughts are and let me know if there's something else I haven't thought of. These dryers are simple things to work on, I think. I know this brand doesn't have the best reputation.

So, I took the thing apart, and removed the heating unit and replaced with another one. The original heating element was fine, not grounded to chassis or broken.

The original temp cutout fuse/thermal fuse was in fact tripped and this was par for the course if the heating element experienced a "run away" condition, which would cause the overheating condition. A new heating element comes with a new thermal fuse and a new high temp cutout thermistor switch.

Fast forward few days, after the new heating element unit got installed, that includes the high temp thermistor cutout (circled in red)and a new thermal fuse, the HE fault code is still happening. As predicted, the thermal fuse did open up, thereby protecting the dryer from a runaway heat condition. The top of the drier did get hot and she reported of a "burning" smell.

While looking at the new heating unit, I did notice signs of excessive current getting drawing. The red (hot) wire insulation did melt and the wire broke. So, the heating element is not turning on/off during the drying cycle as intended and simply staying on. Since the thermistor is a high temp cutoff, aka "thermostat", maybe that's the culprit. Perhaps the replacement new heating element that came with a new Tstat didn't actually work correctly from the get go.

I checked the resistance across the old and new Tstat and they both show 0.6 ohm. So, I took both heating units to the appliance store where the GF purchased the new unit from and asked to see another working thermistor. I checked it's resistance and it too showed 0.6 ohm.

Ok, here's where I'm a little confused. This is a thermistor, meaning it's resistance values changes based on the ambient temp. According to the table below, i should be seeing kilo ohm resistance.

At this time, I'm tempted to purchase a thermistor from somewhere, not sure where, but I'm also open to other ideas that I may have missed.

Thanks.

 

[e9999]

that thing does not look like what I would call a thermistor, more like some sort of thermal switch. A thermistor is a variable resistor that is normally used to provide info about temperature to a circuit or CPU, it's not switch per se. Like a thermocouple. They are typically tiny little things. If yours is a thermal switch of some sort, it would show low resistance when in the ON position at low temps. And would show open at high temps. So that 0.6 ohm seems reasonable to me. As far as checking the circuitry, you could try to find out what switches are on or off with a meter as the thing operates.
Have you looked at the fan? Maybe it's not blowing properly at times and the cause of the overheating in the first place. The wire melting could be due to the heater temp not the amps in the wire, as also suggested by the insulation looking worse near the heater. You could try running the dryer disconnected from the vent and watch the air flow and air temperature. I did a bunch of measurements on my dryer and put a thermocouple in the vent when fixing it a while back. Forgot what the problem was, but it was quite interesting to see the thing cycling.

 

[alia176]

that thing does not look like what I would call a thermistor, more like some sort of thermal switch. A thermistor is a variable resistor that is normally used to provide info about temperature to a circuit or CPU, it's not switch per se. They are typically tiny little things. If yours is a thermal switch of some sort, it would show low resistance when in the ON position at low temps. And would show open at high temps. So that 0.6 ohm seems reasonable to me. As far as checking the circuitry, you could try to find out what switches are on or off with a meter as the thing operates.
Have you looked at the fan? Maybe it's not blowing properly at times and the cause of the overheating in the first place. The wire melting could be due to the heater temp not the amps.

Fan is blowing properly.

 

[e9999]

well, if it's not the fan or the vent, then it's probably the high temp temperature cutout switch. But it is strange that the new one would also misbehave. You can test it easily enough by heating it up on a bench and seeing if it opens up at the nominal temperature. I used a hot plate for testing mine, but a heat gun or hair dryer would probably work too. You'd want to try to make sure it does not open at a higher temp than desirable. It does seem like it did not do its job if things melted. Did you check to see if the new one is nominally at the same temp as the old one (should say that on the body).
A long shot may be that there is some sort of short that bypasses the high temp cutout somewhere. Seems unlikely though.
Is that second pic actually the same model as yours and not a generic one? If so, looks like the high temp cutout switch is simply in series with the thermal fuse, so probably an older dryer type of layout, should be fixable.

 

[alia176]

well, if it's not the fan or the vent, then it's probably the high temp temperature cutout switch. But it is strange that the new one would also misbehave. You can test it easily enough by heating it up on a bench and seeing if it opens up at the nominal temperature. I used a hot plate for that, but a heat gun or hair dryer would probably work too. You'd want to try to make sure it does not open at a higher temp than desirable. It does seem like it did not do its job if things melted.
A long shot may be that there is some sort of short that bypasses the high temp cutout somewhere. Seems unlikely though.
Looks like the high temp cutout switch is simply in series with the thermal fuse, so probably an older dryer type of layout, should be fixable.

I'm not sure if you've read my long dissertation but the thermistor in question is responsible for cycling the heating element on/off. When the temp hits the setpoint, the thermistor switch opens up, until it cools down then it re-activates the heating element. Apparently this is how an electrical dryer works. The thermal cutoff switch did its job and failed open when the temp got too high. This is a non-resettable device. I've had to replace this switch every time I've had to open up the dryer.

This is a simple device dude, let's not make it complicated. I'm an EE too, and live in the world of control systems.

I need to figure out if i need to get a new thermistor that *may* display the correct resistance per the picture above. My GF's dryer is electric and mine is gas so I'm thinking I don't have the same exact temp switch.

 

[e9999]

OK. Good luck with your thermistor switch!

 

[PAToyota]

The #1 cause of this is the vent that's obstructed, which isn't the case here.

Did you fully clean the vent? I've seen some truly horrendous dryer vent ducts over the years.

 

[alia176]

Did you fully clean the vent? I've seen some truly horrendous dryer vent ducts over the years.

My GF went absolute berzerk with the cleaning, not that it was filthy by any means. Good suggestion!

I believe I've found this mysterious "thermistor" that is being used interchangeably in multiple videos and also online stores. The snip from the video below shows the guy pointing at it. This makes more sense now.

See if you can follow me! So my thought is that the heating element is experiencing a "run away" condition because it's not being told to cycle on/off based on this mysterious "thermistor". I found this freaking thing FINALLY and it's located on the blower housing, NOT on the heating unit. It is indeed a thermistor and it's an analog device, not a simple switch. I've been testing the hi limit temp switch (not called a thermal cutout switch) , even though it's being referred to as a thermistor. It's showing a closed circuit, or a normally closed (NC) circuit with 0.6 ohm resistance.

When I get to her house today, I'm going to pull the dryer apart and test out this thermistor to see if it reads the correct kohm number based on the ambient temp. I bet it's shot and doesn't know the temp of the hot air so it keeps leaving the heating element ON and not cycling it.

If my lower back isn't so pissed off right, this would have been an enjoyable experience.