Bicycle Mechanics - Shimano Altura shifters not answering helm

I picked up a Diamondback Sorrento for cheap today. It has Shimano Acera X derailleurs and Altura shifters. The derailleurs seem to be in proper order; they both move freely and don't appear bent or otherwise damaged. However, pressing either lever on either shifter produces no result; it doesn't move the cables -- and hence the derailleurs -- at all. I'm basically an old bike guy; friction shifters I understand, but this is my first experience with indexed models. What should I be looking at here?

the shifters may be worn out. look into some deore shifters or sram attack

the shifters may be worn out. look into some deore shifters or sram attackYeah maybe, but the deralier cable tension may but totally hosed. www.parktool.com repair section for derailer adjustment how to.

The cables are probably loose, jammed with crud, or broken.
Replace the cable/housings and try again.

If your shifters are not moving your cables at all, then the main problem is probably in the shifters (where you don't feel any resistance in the shifter, then something is stuck in the mechanism)- spray the heck out of the insides with WD 40 and work at them to loosen them up. There may be several things going on in the drive train (and probably are) including the cables. But try the easy fast things first- lube the shifters, then check for problems with the cables- especially where they go into the housing and pass under the bottom bracket. You'll probably end up wanting to replace the cables and housing anyway, but try to loosen up the shifters first with some spray lube. Those old friction thumb shifters rocked, didn't they? They get snapped up faster than old Campy on Ebay these days-