Upgraded my printer's hotend about a year ago to the E3D V6 Lite. Worked amazing for about a year until recently I started getting thermal runaway errors on my Ender 3. I've tried everything from replacing the power supply to replacing the board, replacing the thermistor and heater cartridge wires but nothing I've done has helped alleviate the problem. I noticed the issue tended to happen after the first layer when the parts cooling fans turned on. It seems the printer has trouble staying at the desired print temperature of 222 C as it begins to drop after the fans turn on. Any information or help with issue would be greatly appreciated!
If it's being triggered when the part cooling fan is turning on it indicates that the part cooling fan is either pointing directly at the heater block/ nozzle rather than just below it. - double-check your duct hasn't warped and changed direction. The second thing to do is run a PID tune at the desired printing temperature with the part cooling fan turned on as this will give you more consistent temperature temperature readings when the fan turns on. After that you may wish to assess whether the part cooling fan being set to 100% is required for all prints, often you will be able to get away with lower fan speeds without an increase in stringing. - parts that require overhangs will still want a high part cooling fan setting however.
I did find online previously other forum posts that suggested that as well but it's not an issue with PID or warped duct. The Heater Block has a silicone sleeve over it and I've even gone as far as running PID tuning while the fans are on at 100% speed. Thanks!
Can you take an ohm reading of the thermistor and heater cartridge? I'll need the ambient temperature reading when you take the thermistor reading aswell.(not from the printer display)