LakeShore 336 heater output failure

Andreas, I apologize for the delayed response as our system did not notify the support department that you had submitted this issue.

The Model 336 firmware most likely does not have a bug as it can operate a heater at 100% power output for days at a time without failing. However, there is a difference in how the heater protection circuit operated in the Model 340 verses the Model 336. In the Model 336, the protection circuit is looking at the resistance of the heater and if the resistance exceeds 500 ohms, it will shut down with the heater short error. On the low end, it is 5 ohms or less it should shut down with the Heater Short error.

What I recommend you do is turn on the heater diagnostic page by holding the display setup button in for about 5 seconds. When you hear the beep, release the button and the diagnostic screen will appear. Run the heater while monitoring the screen and see what heater resistance is displayed. If the resistance is incereasing and eventually gets to 500 ohms, that will cause the controller to shut off.

Let me know what you see especially when the shut down occurs