Chromatography Forum

Yes, we are still running multiple 7673s! Out of three, one tower is currently functioning

This is actually an error I have seen before, and I am pretty sure we had a spare motor on hand to fix it - what's happening is, with a 2uL injection volume, the plunger carrier will occasionally miss the second position on the little plastic ratchet and jump to the third position, resulting in a 3uL injection. There is a small motor with a spring that controls the ratchet, but I can't seem to track down this part on the Agilent site, nor can I find a detailed schematic of the tower.

Anyone know this part number, or if there's a simple fix?

As far I remember - there is plastic wedge under the motor, it is used to adjust tension in driving belt.

Try to insert the wedge deeper, just one click.
This can help not miss the "stops" on plastic "finger" while sample loading.

It can also be the plastic "finger" with the stops that is not moving back into position fast enough. That is a simple solenoid that moves the plunger attached to the finger. If it gets dirty it can move slowly and the motor pulls the plunger past the stop before it moves back into position. Usually a little WD40 will clean the plunger and get it moving faster again.