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.