Continuous A-01 Error

At Aillio support’s suggestion I updated to Firmware 562 beta. Ever since I’m getting an A-01 error throughout the entire roast and cool down cycle. I have recalibrated my fan, the impeller and chaff filter are spotless and I don’t have an external fan running.
Any suggestions on how to fix this? Is it possible to revert back to an earlier firmware version?

The newer f/w will generate the A-01 warning if exhaust fan is stopped or if fan speed is less than 400 rpm. Perhaps re-running fan calibration would help… ??

Other than that it sounds like it’s time to contact Aillio Support.


Note: from the on-line manual:

Fan Calibration

It is possible to re-calibrate the fans so each fan setting is more linear. If you change your fan motor then you will need to calibrate your fan again.

Follow these steps:

1. Take off your chaff collector (note: NOT just the chaff filter)
2. Turn on the Bullet and go to the menu section 6 by clicking F1 until the clock LED shows 6.
3. Press the “A” button (top left button) If no calibration has been done before this should start the process.
4. Start the calibration process by clicking both fan Up and Down buttons at the same time.
Now the calibrations starts and this can take about 5 minutes to complete. When it is finished the Bullet will beep for two seconds and flash P8D.
5. You can toggle between un-calibrated or calibrated fan speeds by clicking the “A” button in menu
6. 3 dashes - - - is un-calibrated and P-d means calibrate

Thanks for the reply Bruce. Finally heard back from Aillio. They said it’s a very unusual problem that they haven’t seen before and had to consult with the engineers. They want me to replace the Power PCB. Looks like I won’t be roasting for a while since Sweet Marias is closed until 12/28. Bummer !

Uh-oh. Unfortunate timing! Bet you’ve been planning holiday coffee-gifts too.

If your Bullet is a V1/V1.5, that power board change should get you at least close to V2. When I received my power board in the middle of this year it had to be shipped from Taiwan as the new 120 VAC board version is (was?) in limited supply. So even if SM was open it might still be an issue of supply.


I’ve got a v2 so no “free” upgrade. I just noticed there is another US dealer and they’re in Atlanta where I live but they only work on machines they sold.

Mmm… should have made this clearer: my power board wasn’t a “free upgrade”. I bought the new V2 power board but Aillio provided the control board as part of a repair.


My A-01 error today was not continuous, but this thread looked to be a good one to tag onto since Bruce had posted the nice calibration info.

Today the error occurred when I dropped the beans and the roaster was in Cooling mode. Rebooting did not help…only changing the fan “F” speed setting would stop the alarm, but only for about 10 seconds. I had done a full cleaning 4 roasts ago, including the impeller, chaff filter and IBTS, etc. so did not think I had blocked exhaust fan, which was the error code description in the printed copy of the manual. Later I found in this thread that it also means running, but under 400rpm.

No problems until the end of my 2nd roast this morning. I could see the impeller spinning, but could not feel any air being forced out the exhaust. I took off the chaff collector and dumped it and checked the chaff basket, all looked okay.

I finished cooling it down by propping open the bean door, and angling the empty bean cooling fan to blow into the turning drum while in Cooling mode, and grabbed a house fan and blew across the Bullet. The Bullet would not go into Shud mode when it cooled to 80C, so I let it get down to 75C and unplugged it. After letting it cool down some more I plugged it in and cycled the PRS button…it was at about 40C and the fan was blowing strong again and no error codes.

At this point I was out of time until this evening, when I caught up on all of the A-01 threads. I’ll look at the calibration, and double check everything tomorrow.

wngsprd, let me update you on my saga regarding A-01 error. I exchanged MANY emails with Aillio over almost a month. I recalibrated the fan many times, replaced the power PCB, updated firmware and replaced the cooling fan motor and impeller. None of this fixed the problem. I finally insisted that Sweet Marias take the unit back and fix it.
When I got it back the unit sounded considerably different than it did initially but has worked fine ever since. I enquired about what was done to fix the problem. Their response - “It was a strange case, but I figure out, the wires most had some short, so I exchange all the wiring from the power PCB to the back PCB where the fan connects, also I upgrade your impeller motor to the V2 version”

Good luck with your problem. Just curious - what’s the serial number of your unit? Mine is 2208.


I guess this is a good reason to keep the box the Bullet was shipped in! :slight_smile:

Yep, I still have the box.

@kkrawford, mine is #1584, and has been working well for 242 roasts, although I had to replace the little IBTS fan in October…got very good support from Aillio and Sweet Maria’s.

The version number is important to know as it affects choices in firmware setup. Before you close out the Trouble Ticket you might ask Aillio Support or Julio at Sweet Maria’s for instructions on how the f/w should be set in f/w setup step 5 (fan calibration). When I went thru my own A01 issue a month or 2 ago I ended the fan replacement job with the nagging feeling I might have had something wrong in the f/w settings at step 5 (V1/V2 fan calibration) which contributed to the problem.

Also I should mention that Julio has been super helpful to me during the 2.5 yrs I’ve had my Bullet.


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Interesting that you bring this issue up Bruce. Before ordering the fan motor, Julio asked for a picture of my unit’s motor so he could send the correct replacement. No mention of firmware updates. I put in the new motor but the A-01 issue persisted. BTW I am (and have been) running FW 562. When he had my roaster in his shop he again replaced fan motor that he had just sent with another (different ??) one.
My roaster has been running perfectly since this fiasco so I’m reluctant to tweak anything. “If it ain’t broke, don’t try to fix it !”

I use f/w 579 without issue. I had updated f/w but couldn’t downgrade to my prior version cuz of f/w development activity. Didn’t relate the issue with f/w version but in the newer f/w version I found the fan calibration steps for the V1 and V2 fans that hadn’t been there before. That was the first I was aware of the migration to a new fan in new builds. I went thru so many iterations of f/w upgrade/downgrade and fan calibration it would be conjecture to say it was related. But that uncertainty keeps nagging that I may have shot myself in the foot. As you said "if it ain’t broke… "


Yesterday, I had the first chance to roast since encountering this error 2 weeks ago. I roasted 3 batches and had no problems, but also had done nothing to correct the previous problem, except to confirm I had already calibrated the fan.

Fingers crossed all is good.

Problem returned today at the end/cooling phase of the 2nd back to back roast. I’ve had 10 successful roasts since June 8 before this happened today.

Wngsprd, have you contacted Aillio or Sweet Marias about this? I’m curious to hear what they have to say.

Sorry to be delayed responding…been away. I contacted them both…fast responses from both…most likely solution was to replace the fan motor…My Bullet was out of warranty, so I bought a fan from SM and received just a few days later. I roasted 3 batches in the interim with no problems, so I haven’t swapped it out…but will if any more problems.

Update: Roasted 2 more batches today with no problems…so I have this new fan as a backup.