Hi, I'm new to GC's and I've started working with a 6890 this past month. At first everything was fine but now, no matter how much sample flow I'm inputting, the back inlet total flow is restricted. I've had to greatly increase the makeup flow from the carrier gas, He. I'm testing Nitrogen and Methane right now for a calibration curve. No matter which one is flowing I cannot get the back inlet flow over 39. I tried to test for a blockage by turning off makeup flow and reference flow but everything stayed normal. The back inlet can pressurize so there's no big leak. I don't know what else to try. I'd appreciate any help, thank you.
