Son’s One Up Dropper is sinking when sat on, or when you lean on it and push it down (without depressing the lever). Is it likely a service & seals job, or a new cartridge?

First off, check the cable isn’t too tight and holding the actuator partially open.

You could also check the air pressure although it’s unlikely to be that.

Cartridge is listed as a single item on the exploded diagram so I’m pretty sure it’s non serviceable

If you’ve done what onzadog says, have you tried this? https://m.youtube.com/watch?v=ttWyjHPf02E

One of my droppers did this, but as said above I just had the cable too tight because I’d raised the seatpost a tiny bit in the frame by mistake.

As Onzadog advises but chech the pressure with the post extended while you are at it.

When this happened to mine it was the cartridge. Replaced under the two year warranty.

check all of ther above and check the lockring hasnt come loose. mine had. contact one up if you cant solve it, they are always great to deal with

Also if the post has slipped down in the frame and the cable/actuator is being squished this can happen. Raise the post slightly if so.

If you’ve done what onzadog says, have you tried this? https://m.youtube.com/watch?v=ttWyjHPf02E

@stwhannah … that’s for a reverb … any idea whether it works for other droppers?

@hardtailonly the YouTube comments suggest it’s worked for quite a few different varieties.

Update. All fixed and working like a dream. Gunked up and loose cable, gunked up spring in the actuator. WD40, oil, trimmed the cable outer, reassembled, put in the right amount of air pressure, and all is good.

Cheers for the advice all!

Another update!

Worked OK for a ride or 2, now it won’t stay up OR down! Had it out and stripped it down. Assume its the air cartridge?

Warranty job. New cartridge.

Warranty job. New cartridge

Came on a used bike my son bought, almost certainly outside of warranty period.

Drop a line to OneUp and see what they say. They recently sent me a brand new outer/lower tube as the thread on mine wore out after three years.
Otherwise buy a new cartridge, I don’t think there’s anything else you can do.

Sounds like it’s acting as if the lever is permanently pushed? If you’ve got it apart then I’d check that the activating pin is moving freely inside the cartridge post and that the external trigger mechanism isn’t gummed up. Though if the pin is out of the cartridge and it still collapses I’d go for the new cartridge.