Error 42 (75C) IBTS casing temp too high

I got this error message this evening when preheating.
I was preheating to 509F (265C) and got the alarm about the time that I was expecting the charge prompt.

The PCB temp from info was 72

the front display was flashing and beeping

Any clues?

I found an explanation:
If using IBTS the micro fan might not be running

Did you by chance note the IR Fan speed? It’s typically about 16,000 RPM but if it falls below 5,000 RPM you’ll get an error (sorry- don’t recall the ErC but I think it isn’t 42). From your explanation it sounds like that fan speed wasn’t the issue but rather that the fan failed to keep the IR sensor space sufficiently cool. So…

You probably need to contact Aillio support and start a trouble ticket. And Support may be able to offer a proper explanation. Just guessing but if the fan was at the proper speed then it suggests the local ambient was too hot. If you keep track of the ambient when roasting, Support will want to know what it was. I’ve roasted successfully at ~87°F but my preheat is only 401°F.

If a new fan is necessary, replacement of that fan is relatively easy. Reconnecting properly on the way out after replacement is the main concern so take photos on the way in. And be sure the fan rotates freely after mounting.


The IBTS fan was around 1600. Ambient was low 80s. The preheat was higher than what I normally do. I was using someone elses roast as a playback.

I did 2 roasts after that and turned down the preheat to ~460F

I will try another roast today and see if it happens again.

I currently have a thin aluminum baffle to direct the heat away from the underbelly of the beast.

On the positive side: The chaff collector sock worked great.

If you really mean 1,600 RPM and not 16,000 RPM, then you have a problem with the IBTS fan.

If 1,600 RPM was a typo, then yeah, the ErC may well be an ambient temp issue. Especially in light of successfully roasting at a lower Preheat setting at similar ambient.

Just an aside- there is a fan at the rear of the Bullet that directs air to the drum as well as the power board (it’s visible when the chaff collector is removed). You’ll want to be sure the air flow from that fan toward the power board isn’t being diminished or defeated by air pressure from a reverse direction.


Ooops, Meant 16,000

Thanks for the info about the other fan in back.

There is actually a Hack where people are taping off the air entrance to that fan so that it doesn’t cool the air in the drum and gets more convection heat transfer. I’m not a fan of that idea. (I didn’t mean to be punny about that…)

That hack would block the air source for the exhaust fan… not a good plan since air would have to enter below the door, travel vertically to the exhaust duct, then leave the roaster without ever having passed thru the drum.