I am a complete noob about adjusting a front 3 speed derailleur. I am having trouble getting the barrel adjuster for the front derailleur to either tighten or loosen the cable. I am wondering if the barrel adjuster threads are stripped and perhaps I need a new shifter. The shifter in question is a Shimano st-ef50-L


Currently the cable tension when the chain is on the smallest chainring is just tight enough that the cable doesn't sag or flop around. When the chain is shifted to the largest chainring the cable is tighter. Also, when the chain is on the small chainring the cable moves in and out from the barrel adjuster about 1/8th of an inch but it tightens up when shifted to a larger chainring. Here is a video showing what I mean (please excuse the heavy breathing lol):




Do you have any suggestions? Does the shifter need to be replaced?

Take the slack out of the cable at the pinch bolt, then fine tune with the barrel adjuster. Make sure limit screws are ok and cables are good.

Is the barrel adjuster tightened all the way? Can't tell from the video. Start by doing that. If it never tightens (right hand thread), it's stripped or broken. That happens.

If it is stripped or broken, it's usually repairable. That's another topic if needed.

So far the OP is stating a common situation WRT the cable's initial "tension" (actually it's length, the tension is up to the der's return spring). What I don't see in the vid is trying to change the adjuster's position within the shifter, "tightening" the cable. Not sure why the OP didn't try to unthread the adjuster more then they did, only a brief touching of their fingers to the adjuster but no obvious effort to unscrew the adjuster.

I do try to set the cable clamping so that there's less cable slop to begin with. This way the adjuster only has to be unthreaded a small amount for good "tension" and more adjusting capacity remains for future tuning. Andy

The cable tension really only matters on the middle chainring. The adjuster lets you fine tune the FD on the middle ring.
The FD location on the small and large chainrings are controlled by the H & L stops.

Sort of but not really. If the cable has enough slop then when shifting to the large ring the cage might not travel far enough to even touch it's limit. By the same token with too much cable tension when shifting onto the inner ring the cage, again, might not travel inward enough (and not engage that limit). Andy

Looks ok to me. What's the problem?

The video you posted shows nothing unusual, that I can see.

Have you tried the basic adjustment routine?

You shouldn't be worried about cable tension in the smallest chainring. The low limit screw sets the position of the derailleur over the small chainring. The necessary cable tension to allow proper shifting into the other chainrings often results in the cable being a bit slack in the small chainring position.