What would cause my 5890 FID to state it is at 300C, but feels only warm to the touch?

I have a 5890 GC running ASTM D2887, simulated distillation. It is equipped with a FID and recently we noticed the FID won't light. Flows are good and gases are good. Looking at the setpoint/actual reading, it states it is at the correct temperature (300C), but we are able to touch the FID mount comfortably, which is unusual. We have other GCs whose settings are at 250 and very much feel too hot to touch. I have confirmed the insulation around the FID is still there and hasn't wasn't touched before the issue started. I have switched out the cables coming from the board to the detector and this did not resolve the issue. I checked all the Fuses, they are all good. Does anyone have any suggestions on what to check next? Thank you. 

I will also add, that after switching out the heater lines for the detector, it took about 20-30 minutes to even get to it's maximum heat, by feel. The reading on the GC claims it took only a couple minutes to obtain a temperature of 300C, but at this point, the detector was room temperature. 

  • Hi  thank you for participating in the Community.

    I moved your question to the GC Forum for better visibility.



  • Hello  ,

    Generally speaking, when an instrument reads a certain temperature and the actual temperature is not matching that value, it could be an indication of a couple things. My first assumption would be a bad sensor, especially if that is the only heated zone that has the problem. The second assumption would be a power board that is failing, and I think is more likely to be the case if you have multiple heated zones with the same problem.

    That being said, the 5890 is quite an old model and it has reached its end of support date. I am personally not familiar with that model, so I am not sure if there could be other causes for the behaviour your are seeing.

    Lastly, I would suggest measuring FID temperatures with a temperature probe instead of touching it by hand, especially if you are testing it at 300 degrees C.

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