I have started receiving Error 42 again. During the last roast session that I did a few days ago, I was able to roast two 750g roasts, and then got ERROR 42. Today I started getting ERROR 42 at the end of the first roast during the cooling cycle.

I checked and watched the Info window and the IR ambient was in a safe range (around 70) up until I pressed the PRS button to cycle into the cooling mode. The IR ambient ramped up to 80 and the ERROR 42 80 started flashing and beeping and continued until the IR ambient dropped bleow 80.

The IR Fan RPM was in the 16,000 range.

I did a thorough cleaning of my bullet yesterday and took off the faceplate cover off the control and checked the IR fan and it would spin freely with gentle air pressure from a can of dusting air. (you should never use high pressure air on a DC fan motor)

The Error on the front of the Bullet was displaying:
ERC 427
then ERC428
then ERC429
then ERC527
then repeat until the temperature dropped below 80 for the IR ambient in the info window.

Preheat was 527

Firmware = 605
Latest software.

Can you please try version 610? This helps with the IR ambient.
Normally we see the IR ambient error if there is not enough airflow - e.g. your chaff filter is clogged up. Please check.

Thanks Jacob,
I will update the firmware to 610 before the next roasting session.

I am very careful to keep the chaff filter clean. I purchased an extra chaff assembly and swap it out between roasts when I am doing back to back roasts with high chaff natural beans.

I checked that the fan was working correclty by powering the Bullet into roast mode and then turning down the heat power to zero and then ramping the fan up and down. It change the air flow volume as expected.


I had exactly this problem, and found that I had to disassemble the front panel to get to the fan side of the IBTS, and saw that the fan was plenty-fouled with fuzz, most likely from the large amount of natural process beans I roast. I took a soft brush to loosen the fuzz, then vacuumed it out, and have subsequently seen my IBTS casing stay below 60°C.

It’s been a few years and many, many kilograms of coffee since I installed the IBTS, so having to do this every blue moon isn’t too unreasonable (IMO). Maybe the newer firmware will make that even less-frequently required.

Thanks Dylan,

I disassembled the front panel and took a closer inspection of the IBTS fan, and it is in pristiene condition. I only roast a couple of kilos a month and most are light roasts. But most are Naturals.

I have updated the firmware and will roast a couple of pounds this weekend. (hopefully)

This is an unusual situation. I hadn’t had any problems with this error for almost a year, and then it popped up. I didn’t change anything.

Matt from Aillio suggested that I point a fan at the fron of the Bullet. the cooling air for the IBTS sensor enters on the right lower quadrant of the front panel.

Edit: The fan in the photo looks dusty, but it was not. It was very clean.

I updated the firmware to 610.

I roasted two 750g batches of Natural Ethioipians this evening with no problems.

I changed the MERV8 filter that goes to my Range hood (in the garage). It was smutzed up pretty bad.

I also used a small fan pointed at the inlet for the IBTS fan.

I don’t know why but the IR Fan rpm only went to 14,000. It used to go to 16,000. I don’t know if this is firmware related.

The IR Ambient temerature never went abaove 38C.
I will try again without the extra fan and see if the temperature rises.
(It’s an engineering thing, I need to know that caused this. LOL)

Thanks for all of the help and advice, friends.

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What was the result or what did you surmise?

I made a modification to my Bullet. ( Yes, another hack )

I installed a 25mm fan on the outside of the IBTS air inlet.

I used a diamond hole saw (because that is what I had on hand. It actually worked well because it was grinding away the plastic housing and didn’t ‘grab’ like a regular hole saw would have)

Internally, I pulled 5 volts DC off of the USB port for the LED light.
Now when I power up the Bullet, it automatically starts the fan and helps to keep the IBTS cooler.

I ran 2 roasts tonight and the IBTS temperature was 10 - 15 degrees cooler than it was without the fan. It averaged around 48 degrees. Before it was over 60.

I like it. It is clean and I don’t have to pull out another fan and aim it at the face of the Bullet.

If you are not comfortable dealing with electronics, you probably shouldn’t try this. It involves soldering and using a multimeter.