TCD B in GC 7890A not giving the peaks

Based on the chromatogram on the right, it looks like you're analyzing natural gas.  Can you please share the plumbing diagram and method parameters?  It looks like the injection valve isn't turning for some reason.  What has changed on the system between when it was working and when it wasn't working?

Thank you for your reply lance

Yes we are doing natural gas analysis. Below are the parameters and plumbing diagram.

It appears that valve 2 is switching, as there is a baseline spike around 1.5 min in both chromatograms.  I presume this is valve 2 turning back off.  I would measure the actual column flow at the TCD.  Turn off the filament and reference flow to do this.  You didn't list any parameters, but 1/8" packed column flow is typically 20-30 mL/min.  Your flow may be set incorrectly or there may be a large leak somewhere.

It appears that valve 2 is switching, as there is a baseline spike around 1.5 min in both chromatograms.  I presume this is valve 2 turning back off.  I would measure the actual column flow at the TCD.  Turn off the filament and reference flow to do this.  You didn't list any parameters, but 1/8" packed column flow is typically 20-30 mL/min.  Your flow may be set incorrectly or there may be a large leak somewhere.