Road bike: can't shift down on front gears I only have two chainrings on the crank. The chain is stuck on the big one. When I hit the button on the shifter to shift down I am not seeing the cable move at all which is odd.
Not sure where to start, I can take pictures if I need to. The bike is pretty old and has been through a lot of abuse to be fair. With California closing indoor things again today I am looking to fix this myself instead of at the local bike shop.
Pictures
Either the shifter, cable or derailleur is stuck.
Detach the cable from the derailleur, check the derailleur will move through its full range of motion. Tension the cable by pulling in it with a pair of pliers. Work the shifter and check the cable is payed out and pulled in smoothly. You can also pull the cable housing away from the shifter to expose the cable, grip the cable (gently) there, tension it and work the shifter. That should tell you what is jammed.
Often the cable gets stuck in the cable housing due to dirt, dried up lubrication or corrosion. Replacing the cable and housing is relatively easy and inexpensive.
If the derailleur is jammed you may be able to get it moving by applying a penetrating oil and pushing the cage back and forth to free the mechanism.
If the shifter seems to be the problem things can be a little trickier. The mechanism can be contaminated with dirt or corrosion, but sometimes shifters break and the only recourse is to replace them.