FID fault

Is the FID signal moving? If it's grounded somewhere e.g. the collector touching the top of the jet or the spring not seated correctly, it'll be a static high signal (usually around 9 million pA from my experience). If it's moving a bit though this is less likely and you might want to try switching the GC off and disconnecting the FID electrometer from the main board, waiting about 10 seconds and plugging it back in again. As daft as it sounds this has solved at least two issues exactly like this that I can think of.

Is the FID signal moving? If it's grounded somewhere e.g. the collector touching the top of the jet or the spring not seated correctly, it'll be a static high signal (usually around 9 million pA from my experience). If it's moving a bit though this is less likely and you might want to try switching the GC off and disconnecting the FID electrometer from the main board, waiting about 10 seconds and plugging it back in again. As daft as it sounds this has solved at least two issues exactly like this that I can think of.

Thank you all for the replies,

The FID signal goes up and down a bit.

Shut down and restart was my initial thought but due to the GC operation requirement I cannot shut down and cannot open the glove box until June next year. 

Is there any way I could safely reset only the FID?

Thank you,

tbh, if your signal is consistently as bad as above I'd say you won't be able to use the GC at present so the requirement for operation is mute, but that's just me. If you can get to the right side panel where the main board is located via the glove box then you can disconnect the FID electrometer from the main board whilst the GC is on but I wouldn't recommend it!