LakeShore 335, heater automatically turned off

Jianmei,

The Heater 1 Open error is saying that the Model 335 has detected that the resistance of the heater exceeds approximately 500 ohms. When you start the heater, do you see the temperature of the control sensor start to increase and then the error appears? If yes, what may be happening is that as the system starts to warm up, one of the wires going to the heater is going open which causes the error. If you do not see the temperature start to go up before seeing the error it may indicate an issue in the Model 335 heater circuit.

The first thing to do is to disconnect the heater from the rear of the Model 335 and measure the resistance across the prongs of the dual banana plug looking back at the heater. If it reads greater than 500 ohms, you will need to investigate that circuit. If it reads normal values which are normally around 25 to 50 ohms, reconnect it and try to do an experiment.  Monitor the temperature and see if the open error appears at he same temperature each time.  If it does, then the open is due to an issue in the system you are using and you will need to contact that manufacturer for troubleshooting procedures.  If not, let me know the details of the failure and we can do additional Model 335 troubleshooting.