For those who can offer an advice, My Agilent 6890N got Thermal Shutdown during the regular running. What exactly the problem is and how to overcome this fault? Thank you for all the attention to this message.

Thermal shutdowns occur when one of the heated zones cannot reach its setpoint. For example if you are running a temperature ramp and the oven for some reason can't keep up with the requirments of the program you will shut down. An oven temperature shut down can also occur if the ambient temperature of your lab is very warm and the oven cannot reach a low enough temperature.

Hardware or software problems can be the source of the inability to attain a specified temperature. I have corrected oven temperature problems by re-installing my Chemstation software, but your problem may be related to your instrument.

You need to do some more investigation of your instrument hardware before anyone can be of help to you. You should really contact Agilent for assistance.

When a oven vent sticks open or is blocked shut, you may exceed the Thermal limit of the instrument (how fast it is supposed to increase or decrease in temperature)and the oven will shut down.

Check the operation of the vent and make sure it is opening when it should and closing when it should. Make sure the exhaust is not partially blocked so the oven can cool down properly if needed.

Set the oven to high temperature and feel for hot air exiting out the back; we've had to replace a couple of the flap motor actuators. While heating, you shouldn't be able to feel hot air coming out the back, if so it will never reach temperature. When cooling, then you should be able to feel hot air exiting out the back. You can do this repair yourself if that's what's wrong.

Thank you all for reply. We set some desired T, but the oven does not work! It shows OFF. I checked the vents and they are fine. Our room temperature is ~25C. It is a one-year old GC. The wired thing is: our original method is using AUX 2, but after the shutdown we found that the AUX 1 was selected by itself. We checked the AC board, it is fine. The next step is going to change the main board, which is not what we want. Any suggestions? Thanks in advance.

call Agilent 1-800-227-9770 and get their free telephone advice. At 1-year, they may even cover it with warranty, doesn't hurt to try.

The bad thing is we just passed the warranty. I called and a new main board is recommended to buy. :(

A thermal shutdown is caused when the particular component (in this case the column heater) draws too much power from the GC compared to the expected power requirements for a set temperature. The main cause of this is usually a faulty heating element or a short on the heater sensor. As you have probably found, you need to turn your GC off and back on to reset the error. Set the GC oven to 200 and after around 10 seconds open the over door and feel if the heating element is working. Don't touch the element just feel if there is any hot air in the oven. If there is, shut the oven door and note the rise in oven temperature on the front display. If it jumps around then the heater sensor is at fault. It's unlikely that you would have to replace the main board as this only distributes the power to each component and does not affect the actual power drain.

The oven shroud assembly contains the heater and sensors.

It would be best to get a engineer to look at it as the main board is probably very expensive.

I restarted the Chemstation, not reinstalled it. A software person from Agilent said that my problem has nothing to do with the Chemstation.
I fixed the Method Resolution problem, but all my heaters do not show "on". When I check the "on" box, it gives me error message. Is this really a mainboard problem? :(