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Gene Cafe Lifespan
Hi everyone,

Our roaster has faithfully toasted delicious beans 2 or 3 times a week for 8 years. At the end of the last roast, I noticed that the GC drum was struggling to rotate at a specific point in rotation, with a noise indicating that the drum motor was working a bit harder. After a few rotations like this the drum locked completely and the machine went into cooldown mode with an E3 error. Uh oh!

I disassembled the machine (side-note: who else thinks the repairability of these things is fantastic?) and noticed that all of the screws on the right-damper assembly (this: were loose. The loose screws stuck out from the assembly and prevented the drum from rotating (see picture below). I tightened them up and gave it another go, and at the end of the next roast the same thing happened. I suppose the threading on the assembly is stripped.

A new assembly is $25, but I thought I'd ask your highly-educated opinions: How long have you guys managed to keep one running for? I take good care of it, and replaced the heater element and fan a year and a half ago, but the machine is definitely aging (roasts are taking somewhat longer, plastic is getting brittle with heat exposure, general grime buildup that is getting harder to clean, etc). Should I dump this one and get a new one, or repair the part and hope for the best?

Thanks everyone,
mattadam attached the following image:
well, I would guess that depends on if you have tried to make those screws stay tight, I think lock tight has a high heat sticky stuff that may hold those screws, maybe a tad bigger screw here and there...

the assembly seems priced right so I would most likely see if I can fix it you may be able to part it out if it does not work correctly to get some of the 25 back...

the big question is do you want a new roaster as I know many folks who will find any excuse to buy up...


Mark McCornack
Hi. I?m new to the Forum, but I have to throw my hat in the ring on this one. I have a Gene Cafe that Iv?e kept going since 2007. Like you, I roast 2 to 3 batches a week Over the years, a couple of heaters replaced, an inlet temp sensor, and a fan. Currently, my back is to the wall as I need another inlet temp sensor and the part has apperantly become obsolete with nobody who can tell me what it was so I can attempt to find a replacement component on my own.
Anyway, otherwise, I?m very happy with Gene Cafe. Enough so that I just bought a new one (though I still want to revive my old workhorse). The only thing I dislike in the new roaster is the ?Nanny Alarm? that goes off at a couple of intermediate temperatures during the roast cycle demanding user intervention. At $600-ish, it still amortizes out to a pretty sweet deal.
I am not aware about any inlet temp sensor exists in Gene, and yes opened it for modding.
The bottom side center component you can see in the picture above is a thermostat, for safety only, tripping at a maximum temperature, and reconnecting when heater cool down
Not sensing/reading degrees, or regulating the hot air in any way.
Now I am confused.

What are these parts? (from the Gene Cafe site)
JackH attached the following image:


KKTO Roaster.
As notice say, the blue cable sensor is for a newer version of CBR-101.
My post was about the older version.
No idea when they changed the models, I would change the model number too, keeping the same code is misleading.
Noticed also there is no mainboard offering, nor old or new, so...
The old model had no sensors at all? Must have been roasting by time only.

KKTO Roaster.
Mark McCornack
Yes Jack, that is the sensor. To my understanding, this switched over somewhere around 2017. WHY it changed, and FROM what TO what is still shrouded in mystery. The Gene Cafe USA site also has some DIY Diagnostic notes which indicate both inlet and outlet sensors should be in the 220k to 380k Ohm range.
Unfortunately, the Gene Cafe USA site has been unresponsive to my inquiries. I can?t get a callback from them. I?ve even reached out to Korea on this, and despite the language barrier, my contact was quick to respond. The only thing he could tell me unfortunately, is that the old sensor became ?unavailable? from their supplier. He was not able to tell me anything technical regarding a spec change or any other motivation for a functional change calling for a mother board change.
Is there anywhere else I might find someone with actual expertise on this roaster that could shed some light? seems to be a dead end.
Regards, Mark
Edited by Mark McCornack on 06/25/2020 12:16 PM
The older model use the outlet sensor for the display, and also for heater control logic, which is very rough, on-off relay (mechanical, not ssr) with very high inlet temperature swing, in the 50 C ballpark, as in the 250-300C range.
Indeed was a good reason to change the approach in that area, the new model probably use a controller like PID or PWM, if they adopted a sensor as for outlet.

What happened that you need to replace the inlet sensor? What are the symptoms?
Mark McCornack
In the DIY diagnostics (from, the recommended places to check when receiving an error code are heater resistance (around 10 Ohms), and the two thermistors (temp sensors). They are both supposed to have a nominal R of 220k-380k. The outlet sensor measured 250k and the inlet sensor at the heater box measured >4 Megohms.
I had this same problem a few years ago (before the sensor availability went away) and replaced this sensor which resolved the Problem at that time. My understanding from some online research is that this is a safety issue. The sensor is there at the heater box to insure that the unit is aspirating alright. If the chamber is overloaded or choked with chaff, excessively hot air will build up there with nowhere to go. Fire hazard. Safety issue.
What damage them, and also that make difficult to find, is the high temperature... because an ordinary NTC is rated up to 200 C, while the temperature inside the Gene heater exceeds 300 C.
Even the internal sensor to wires soldering can be damaged, just think that the typical solder melts between 230 and 260 C. For such hi temp sensors the should use high temperature soldering too.

Didn't found anything closer to any of the major components sellers: farnell, mouser, digikey or rs.

I would try to replace it with a 250k potentiometer, mounted outside heater of course, and fine tune a value that please Gene logic.
Obviously, the safety functionality of the inlet sensor will be void this way.
Mark McCornack
Yes, renatoa. I did think of just putting an external resistor there, but I really don?t want to defeat this as it is primarily there for safety.
What I would REALLY like to know is, HOW (electrically) does the ?new? sensor differ from the ?old? sensor? From the genecafeus site, the implication is I can put a new sensor in an old heater box, but I would need to replace the main board too. So, apperantly, it?s not a mechanical compatibility issue, but rather an electrical one. So, what is the difference? It sure would be nice if the US representative for Genesis ( would reply to my inquiries!
Mark McCornack
Hi. I have some followup information for those interested in the legacy hot air inlets sensors on the Gene Cafe. I believe this to be accurate based on my own empirical experience and research.
The current inlet temp sensors (after 2017) have a nominal 25C resistance reading of around 250K, and R drops with temperature increase. The older sensors have a nominal reading of around 4 Megohms at ambient and also reduce R with increased temperature.
If you go to the website, there is a a DIY troubleshooting guide which states both inlet and outlet temp sensors should be In the 220K to 380K range. This statement DISREGARDS THE AGE OF THE SENSOR (pre or post 2017). So, in the case of a pre 2017 inlet sensor, a reading that is 10x to 20x higher than stated in the troubleshooting guide may be normal and your sensor may be just fine.
With respect to interchangeability between newer and older main boards, it?s a different story. If however you have an older roaster like mine, do not assume that a 4Meg inlet sensor reading means that it is bad and replace it based on the DIY troubleshooting document published at
This is all just based on my experience with three old style sensors, all of which read in the 4Meg range.
This is very strange value 4 mega... major sellers current offering for thermistors tops at 1 mega.
There is no advantage to design a circuit using such high value, because will make it extremely sensitive to noise... or... the sensor wires aren't shielded, as I see in the pictures.
I don't question your finding, but... what is the source of this info ?
Edited by renatoa on 06/30/2020 2:13 PM
Mark McCornack
Hi renatoa. I agree with you 100%. This is a pretty high resistance, but this would be at 70F. I monitored this resistance while doing any empty chamber run up (220K fixed resistor across the pads on main board to fake out the roaster), and saw the resistance drop down to around 100K at 300F. So, in normal operating, the resistance drops considerably. Anyway, that?s my source of info. Empirical measurement.
Also, someone at Genesis in Korea was nice enough to send me an old style sensor they had laying around. It corroborated the 4Meg measurement. About 3 years ago, I replaced this sensor as well. This was back in the day when the old style sensor was still available from genecafeus. It too was 4 Meg. I do totally agree with you though. This seems very high. Then again, at its normal operating point, it would be <100K. The trully odd thing is nobody at the factory can tell me what it is and I can?t get anyone at genecafeus to respond.
Many thanks for Mark's posts here! Yesterday I got the dreaded E4 error on my 2010 Gene Cafe. Following GC USA's troubleshooting guide, I concluded that the heater assembly and the inlet temp sensor were both shot. It seemed odd that both failed together, but that's what my multimeter was telling me.

For me, this would also have required a main PCB replacement, and the combined cost was making me wonder whether it was time to upgrade to a different roaster entirely. That might have been very exciting, but it also would have been quite costly.

Instead, Mark's post provided me with the proper resistance on the inlet sensor at room temp, leading me to conclude that I just need a new heater assembly. I've now ordered that part and it hopefully will arrive by the weekend, which will keep me in fresh coffee for the holidays!
Edited by roastini on 12/17/2021 4:05 PM
Mark McCornack
Buongiorno Roastini,
I hope my past experience with this thermistor value is applicable to your situation too. I think having the heater element go out is a consequence of normal use over time, but I would expect the thermistor to be pretty robust and much less likely to fail. I hope this is the case for you. When you get the unit back together, please post on the forum to let us know how it went and if your problem is resolved.
New heater assembly installed, and coffee now roasting!
roastini attached the following image:

Edited by roastini on 12/17/2021 4:10 PM
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