6864 Troubles

Bullet is totally driving me crazy. I got a warrantied fan in the mail last week after writing up a ticket. I installed it and it worked great for 3 roasts😑 A total of 2600g of coffee. Today, I was about to roast for a small order and it happened again.
I ordered a spare with the warrantied fan so I figured I may have gotten a dud. I installed my new fan and I’m getting the code again after it’s plugged in for about 5-6 seconds.
I have some Gesha coming tomorrow or Monday and I really don’t want this to be something screwing up some spendy beans.

*Roaster had a full cleaning with the last fan install. And I only did about 8 roasts after the previous full cleaning

Looks like I can’t even pull up the RPM

Well…the code went away so I tried roasting. I’ve read that others have managed to do this. Anyhow, I didn’t get much past yellowing before the code came back. I noticed a warning light and the fan was at 6600rpm, then 4020rpm, then 0. I lost 1000 grams of a great Sumatran on top of not being able to fulfill the order. I also prelabeled a bunch of coffee bags with roast dates so those are trash too.


Which fan did you replace ? The exhaust fan or IBTS fan ?

IBTS fan… twice🙃

Dumb question. You did fit it the right way round ? I think it would be unlikely for two fans to suffer the same issue so I would also check the connection to the PCB end and see if the contacts are good and secure - maybe as the machine heats up, you get intermittent contact…just a wild thought.

Mine was ultra clean, even the first one that failed. And everything is snapped in tight. Part of me is worried there was just a bad run of fans. Not sure if it’s supposed to be this way, but none of them spin freely. They’re smooth but only make a small turn before returning to position. Never really seen a fan do that

Probably normally behavior. You’re seeing the magnetic poles in the motor stop the rotation. The blades are so short they have very little momentum. The motor has strong magnets and rotating by hand won’t generate enough momentum for them to continue spinning very far.


Got it, thanks. I just figured it wouldn’t have a hard stop like that.

Bruce is right about the magnetic “cogging “ as I think it’s called, not a sign by itself of a faulty fan. It’s usually bearings that give out and that’s a different feel.

The only other factors I can imagine might be if you have the IBTS not seated or wires fouling the fan when you put the faceplate back together causing friction which drops the speed. The fan has a speed wire so that’s how feedback comes back. Typical IBTS fan speed should be in the 14K rpm region, so you might want to watch this during a dummy roast and see if a pattern emerges…

Of course getting @jacob to review wouldn’t hurt…

Since it worked for 3 consecutive roasts, I think I did everything correctly.

Which leads to environmental or other things we know we don’t know…like heat build up expansion or something coming into play. Hence trying to spot a pattern…can you leave the info panel up and monitor the IBTS fan speed ?

No idea, I haven’t tried that before. But Matt is going to call me tonight and we’re going to try to run a roast over the phone if I can get it out of beeping mode.
*Outside temperature affects everything anyway. I’m sure people roast with their Bullets from 55-85+ degrees Fahrenheit with external temps but that fan is supposed to be stuck at 16,000rpm regardless of external temperature. It really seems to just be a fan to protect the system from reaching a failure/inaccuracy point vs keeping it at XX degrees. That’s something a heatsink should be able to do in all but the very hottest environments where that little fan wouldn’t do the job either… I’m thinking Dubai or Phoenix hot, and roasting outside in the sun

OK, I think we’ve got several “fans” crossing the streams here so glad Matt will try and walk through them. Ruling our the exhaust fan (squirrel cage where the smoke comes out) as our candidate, the error you quoted is generally tied back to the IBTS fan which is supposed to keep deposits from smoke off the IBTS lens. You’'re right that the general RPM is in the 14K-16K range and should blow in a particular direction (I heard of folk misfitting them backwards so they suck intsead of blow) and the firmware checks for that as a precaution. It should not be impacted by the ambient temperature (unless you are in Siberia and the fan froze solid!).

There are a couple of fans on the power board which I don’t think are checked by the firmware.

Please let us know how the movie ends though if you and Matt figure it out - enquiring minds want to know…

Will do!!! Hopefully it’s a one and done fix, at least until normal wear takes it out after hundreds of kilos of coffee is roasted.
*The exhaust fan got a full cleaning fairly recently(it wasn’t very dirty anyway) and spins well.

The fan keeps chaff off the IR sensor and assures smoke/dust/whatever doesn’t move upward thru the view port toward the IR sensor. A heatsink can’t do that.


Ah, I know it’s a temperature measuring device so it can obviously get hot. I just figured something in the back of it may be sensitive to overheating.
I wish you could run the roaster without it if need be. Not ideal since that’s a perk of this roaster. But plenty of people roast solely on a bean probe and that’s exactly how I’ve roasted in the past before getting the Bullet.

While that sounds great in principle, the IBTS is used to measure the drum temperature for preheat so if could bypass it, I think you would still be stuck. Having a spare IBTS in a drawer would seem the best option.

Perhaps you have tightened the screws holding the fan too hard? Then it might not spin freely enough. Try to loosen them a tiny bit. You could even do this while power is on to see if the RPM goes up.

I’ll try that. But it worked fine for 3 roasts with the first of two fans I got. Matt even said the RPMs were good for those roasts.