Samsung Dryer DV350AER Thermal Fuse Keeps Blowing @ heating coil!

[blackbird307]

Model Number

DV350AER

Brand

Samsung

Age

1-5 years

Hello all,

I have a customer with a refurbished Samsung DV350AER who initially phoned me about an excessive noise. I had replaced the rollers in it as they had failed and that problem has resolved. A few days after replacing the rollers, customer phoned me back to say that the heat had stopped working. Upon returning with a heating coil kit, I had noticed that the high cut off thermal fuse had blown. I replaced it, along with the thermostat and heating coil. The very next day I received a phone call stating that the dryer had worked once and then no heat again the second time.

Heating element kit included:
- DC47-00018A - High cut-off thermostat
- DC96-00887A - High temperature cut-off thermal fuse
- DC47-00019A - Dryer heating coil

Based on my research the problem could be caused by multiple things such as: DC47-00018A
- Blockage
- Heating coil grounding out
- Bad relay on control board
- Bad thermistor
- Bad thermostat

I have ruled out the above with:
- Investigated ducting and verified there are no blocks and air there is healthy air flow through the exhaust
- There is no visible evidence of the heating coil grounding out, also the circuit breaker in theory would have tripped aswell
- I have read that a bad relay control board could cause this, which makes no sense since if the relay was stuck, the heat would be on the moment you plug it in, also note below point with regards to thermostat
- I tested thermistor and it isn't open or shorted
- Bad thermostat, if it's rated to open the circuit at 260 F and the thermal fuse is rated 320 F. This is the most likely culprit imo.

The thermostat, thermal cut off fuse and heating coil are all in series.

So what I gather above, the thermostat is supposed open at 260F, cutting power to heating element, then re-establishing power at 210 F (50F drop). To me it would make logical sense that if the thermostat was working and opens at 260F, and that the thermal cut off fuse is rated for 320F, it should not be failing. The thermostat is brand new. Why is the thermal cut-off fuse still blowing??? Is it pre-maturely failing or did I install a defective thermostat. Non of this is making any sense.

Based on my research, others are having the same issue, unresolved. Could someone point me in direction of possible cause.

Thanks again

 

[Jake]

This has been a common problem with no solution unfortunately, but the MEDIUM HEAT setting seems to keep it from continually blowing that thermal fuse, look here:

DV218AEB Samsung Dryer Keeps Blowing Thermal Fuse

Yes, electricity will take the path of least resistance....closed relay contacts, or through diodes and such in a meter.....a closed relay will show nothing as the electricity will go through the relay before the meter, once the relay contacts open and the power has no choice but to go through...

www.applianceblog.com

Jake

 

[blackbird307]

I changed the thermal fuse, put original thermostat back in after seeing that it still worked. I put the original heating coil back in. I measured the temperature directly at the output with nothing in the dryer, climbed to 240F, then dropped to 200F then up to 230F, then down to 200F then 215F then 195F, 200F, slowly stepping down. When eventually it got to cooling mode back to room temperature. Hooked dryer to outside duct, same thing, fuse did not blow, seemed to work fine.

I leave. Next day they put a load in and I’m informed shortly after that the fuse is blown.

So the air comes into the rear of the unit, passes through the heating element, then into the duct rear bulkhead and then through the drum, exiting through lint trap to blower motor providing suction, then straight out exhaust. The thermister is mounted on the blower motor. My question is, how is the thermister supposed to know what the temperature is if there is a load of laundry obstructing the flow of air? Wouldn’t you want the thermistor on the intake, not the exhaust since the intake temperature is more likely to be consistent? Also I don’t think that cycling thermostat design works reliably because if it did this wouldn’t be happening. It’s just a safety temperature control for when the computer can’t control the heating element since it thinks it’s too cold, can’t see the temperature properly since not enough air gets to the thermister. Seems like a bad design to me.

Also looks like previous owners bypassed the thermal fuse on the blower motor, which I’m sure would trip aswell.

Will replace thermal fuse and advise medium heat setting.

 

[Jake]

Will replace thermal fuse and advise medium heat setting.

Yes, that's what I would do.

Jake

 

[blackbird307]

I replaced thermal fuse and ran it at medium. Still blew thermal fuse. It seems as soon as you put a load of laundry in, half full, the thermal fuse blows. Changed thermistor, no difference, tested at ~9.5-10k.

Also exhaust temperature never got more than 120F this time around. I guess because it’s medium heat.

My theory is that the cycling thermostat doesn’t work reliably and won’t open sometimes? Or the cycling thermostat cools down faster than the thermal fuse and continuously accumulates heat as the cycling thermostat cycles.

What I don’t understand is why this problem occurs after changing the rollers and tensioner. They spin freely and the drum sits on them no problem. Maybe the motor is damaged from running with bad rollers and doesn’t spin fast enough with fan to properly circulate air??

 

[Jake]

Something else is wrong then, if you put the machine on NO HEAT/AIR DRY, does the heating element still get hot?

Jake