If you hear a click then the lack of movement may be in the cable and housing binding. you need to diconnect from the derailleur and pull the cable by hand and shift the shifter up and down to detect movement. if it moves replace the cable and housing. these shifters are known to have the grease solidify after a few years which causes the pawls in the mech not to work as intended. If this is the case then it is important to flush out the old grease first. these are much harder to bring back to life than the newer trigger style. Either way you need to remove them from the bike, dig out as much hardened grease as you can. Place them in a can and drench them with engine cleaner from the local auto store like autozone. scrub them with toothpicks and old tooth brushes, drench them again with the cleaner if you have too. Then power rinse them with the hottest water you can withstand, sprayer on the kitchen sink is good for this. then blow dry til dry. use a light silicone type lube, soak well. the put cable back in, pull by hand and test for function. DO NOT USE WD-40.
If this does not work, replacement is your only option. you have integrated shifter/lever combination which means you need to replace the levers and shifters if the fix did not work. you will need standard pull levers (not V-brake) of your choice.
yes you will need a 3x7 set of shifter pods and probably new grips. the shifters you need are
SHIMANO SL-M310 ALTUS RAPID FIRE 21 SPEED
No, it is not a $25 job. If you hate your bike so much that it is not worth it. Then sell it to someone for the $50 and make them happy. Then what? what do you do for a bike with $50. The early 90's bike you have now are some of the finest bikes that will ever be made and are well worth going thru to make good user's again. The bike you have could have easily cost $600 or more back in the day. A $600 bike today is junk compared to that. My newest bicycle is a 1997, my daily bike is a 1994 I refurbed a couple years ago to the tune of about $800, no regrets. Its the best. Its all in what you want, just be informed. I would like to see pics of your bike just for fun if you have the time. cheers
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
Thanks for the pics. Yep never seen one of those before. strange to have an alloy bike with Dx shifters like that. The other problem would be the shock,probably cannot get parts for it anymore. If it was cromo steel and rigid it would be a better bike to refurb. Try what i told you first, if it fails then even i would sell it off and start with something else. I just like the retro steelies to redo than waste my money on brand new bikes. good luck and let us know if you got them freed up or not
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"