Samsung Dryer Keeps Blowing Thermal Fuse

[justmore]

Model Number: DV218AEB
Brand: Samsung
Age: 1-5 years

Have a Samsung dryer that's a few years old, Model No. DV218AEB.

The dryer no longer heated up two days ago, so I took the dryer apart and checked for blockages, tested everything with a multimeter for continuity and shorts, and found the thermostat cut-off at the heater had blown. Everything else tested within spec and there were no shorts or any visually obvious issues.

Replaced the thermostat cut-off with a new one (Samsung Part No. DC47-00016A) and put it back together. Dryer heated up fine the first time it was turned on and run for a minute, but then apparently blew the thermal cut-off immediately the second time it was turned on, since it no longer blew hot air again.

I took the dryer apart again and replaced the high-limit thermostat (Samsung Part No. DC47-00018A) at the heating element even though the original tested good. Also replaced the now-blown second thermostat cut-off with another new one. Put the dryer back together, again, worked fine when turned on and run the first time, heated properly, but blew cool air the second time I turned it on. Thermostat cut-off blew again.

Just throwing this out there to get any ideas on what to check or personal experiences on what causes dryers to blow thermal cut-offs like this so I don't keep throwing parts at it. I'm at a loss since there is nothing obvious and looking up the common causes online has only revealed obvious causes such as blocked vents or the high-limit thermostat that has already been replaced with the above results.

There is NO blockage anywhere, dryer is extremely clean and there was almost no lint buildup at all, the vent system goes straight out an unrestricted 4-inch pipe.

I've taken apart the element assembly, the element looks great, has the correct ~10 ohms reading at room temp, and is not touching the housing or any other metal when assembled (verified with multimeter). The thermistor reads the correct ~10K ohms at room temp, and goes to ~7K ohms when warmed and about ~15K ohms when cool. The second thermostat cut-off (right after the blower, next to the thermistor) has not blown and shows continuity.

The motor runs fine and is getting 120V, and the heater relay seems to be working and getting 240V since the element heats up, at least once the dryer is first started up after replacing the thermal cut-off. I've even checked the centrifugal switch at the motor, and while it doesn't read as the exact 2.88 ohms between pin 3 and 4 or the 3.5 ohms between pin 4 and 5 that the troubleshooting manual calls for, it does read at least 2.5 ohms and goes close to 2.8/3.2 so I'm pretty sure the switch isn't causing it either.

There are no error displays or diagnostic codes. Test mode doesn't reveal anything since the dryer runs fine otherwise, just has blown two thermal cut-offs with no obvious cause.

At this point I'm guessing it's the main PCB (Samsung Part No. DC92-00160A) since there's nothing else I can come up with based on the troubleshooting I've done so far. Sure don't want to spend the $$$ only to find out it's not the PCB though.

Thanks in advance for any helpful replies.

[justmore]

Checked the relay on the board with the blue/black wires disconnected, no continuity across the contacts.

Also checked all the wires in the heater circuit (red, blue, black) for continuity and for shorts to ground. Everything checks good.

I connected the two wires that go to the thermal cut-off to bypass it for testing, made sure they had continuity and that everything else in the circuit had continuity and wasn't shorted to ground. Put the dryer back together and ran it for several minutes on both normal and timed dry/high heat modes to check the exhaust temperature and heat cycling.

Checked the exhaust temp and heat cycling with both a 200*F meat thermometer at the exhaust vent and a non-contact infrared thermometer. The meat thermometer seemed pretty dang accurate, even more so than the infrared, which showed about 10-15 degrees less than the meat thermometer, even when held very close to the vent and pointed at the inside walls. Guess they really aren't so great for checking air temperature.

Did the first run on "normal" cycle (which seems to use the moisture sensor) it went up to ~140-150*F on the meat thermometer and stayed there, showed slightly less on the infrared. The dryer stopped automatically on it's own after about 2-3 minutes.

Did the second run right after, on the "timed dry" cycle, with highest heat setting selected. It took a minute to get up to 140*F, then climbed to 150*F after another minute, then slowly went to 160*F, then 170*F, and backed off, taking only 10-20 seconds to go all the way back down to 140*F, where it held for another 10-20 seconds, then slowly climbed to 150*F again, then 160*, and finally 170*F, where it stayed for a 10-20 seconds, then backed off again all the way to 140*F.

So, two complete cycles getting up to 140*F, going all the way to 170*F, and back down to 140*F.

I guess this means the thermal cycling is okay and the cut-off isn't blowing because of high heating element temps.

What else blows a thermal cut-off?

[Doc Ryan]

Can you try running the dryer on the "Air Fluff" cycle for me and let me know if it heats during this cycle?

[KeithDiehl]

Good times with appliances!

I am currently going through your exact story. May I ask if you resolved it and what the problem was?

[Lcwilson]

I am wondering the same thing. I am having the same problem and have replaced nearly everything except motherboard. My fuses are blowing in less than 3 days now. Did anyone find a solution?

[Lcwilson]

Did you ever find a solution? I have the same problem and have replaced the heating element, thermistor, fuses, dryer belt, rollers, cleaned blower fan, vent. I don’t know what else to do.

[fixitrightnow]

Did you ever find a solution? I have the same problem and have replaced the heating element, thermistor, fuses, dryer belt, rollers, cleaned blower fan, vent. I don’t know what else to do.

Hi, Just wondering if you where able to solve the problem with the dryer? Thank you

[Lcwilson]

Hi, Just wondering if you where able to solve the problem with the dryer? Thank you

Another technician said the motherboard will need to be replaced. Gonna have that done 11/10. We will see if it works and for how long. It was a hard part to find. Finally got a refurbished one.