Originally Posted by Mark Booth
Update on our 12 oz. Great Northern machine….
Last weekend, after making two 12 oz. batches of popcorn before the 1st movie, I went to make a third (and forth) batch for second feature. The kettle in our machine heated the coconut oil but then lost all heat and wouldn't pop the corn! DAMN!!
There were a few reports of this problem (Amazon reviews) when I purchased the machine, but I was willing to take the risk because I really needed
a machine with a large bin capacity.
I contacted Great Northern and they have a repair program. The kettle is only warrantied for 30 days! (I knew that going in.) For $24.95 prepaid (plus one-way shipping), they'll repair the kettle (regardless of problem). I got an RMA number but I am concerned about turnaround time. I need the machine every two weeks for the next several months. So, being pretty competent with things electrical, I decided to disassemble the kettle to see if I could figure out the problem.
Turns out there is a thermal fuse built into the circuit inside the two halves of the kettle. It's not much bigger than a 1/2-watt resistor and is connected to the wiring via crimp connectors. I isolated the fuse from the rest of the circuit and used my trusty ohm meter to test it. Yep… open circuit. The fuse had blown. Thankfully, the brand and model number were clearly visible on the thermal fuse. It's an SEFUSE brand, 10 amp, designed to blow at 240º C (464º F).
In addition to the fuse, there's a circuit breaker arrangement mounted to the bottom of the upper half of the kettle. There's a bit of spring metal that, when heated to a certain temperature, changes position and opens the circuit (allowing the kettle to cool). The mounting nut holding this circuit breaker to the bottom of the kettle was somewhat loose. The way it mounts, I suspect that it being loose could affect how well the spring metal reacts to heat.
I tightened the nut on the circuit breaker and replaced the SEFUSE with the exact same brand/model (easily sourced on the web). I reassembled the kettle, plugged it in, and sure enough it's heating again!!
I didn't pop any batches of corn so, at this point, I do not know if my fix is going to last. The problem MAY lie with the spring metal in the circuit breaker not working correctly. If it doesn't respond at the right time, the kettle could become too hot and, pop, there goes the thermal fuse again.
I will add this…. When I went to make that third batch of popcorn right before I figured out the kettle wasn't getting hot anymore, I put in the coconut oil first to let it heat for a bit. Then I FORGOT to add the popcorn within a few minutes. I got distracted by one of our guests and got involved in a conversation. It was about 10 minutes before I realized the popcorn wasn't popping. Oops… I never poured the corn into the kettle! So, the kettle sat there heating (stirring rod NOT turning) with oil in it for about 10 minutes. If the little circuit breaker is designed to open the contacts before 464º F, then the fuse should not have blown. But I'm reasonably convinced that, had I added the corn in a timely fashion and turned on the stirring rod, I wouldn't have needed to replace that fuse. The corn would have absorbed some of the heat and helped keep the temp below 464º F.
I'll be more careful going forward. The machine will get used again this next weekend. We'll see how it goes.