Problem no heat. Cable not moving how to trouble shoot

My 2000 limited wirh 298 k miles Have had no heat all winter. Cable to heater not moving. ( has climate control)
Fluids not leaking anti freeze. Vehicle running g normal temp.
My mechanic just bypassed tbe heatercr valve. No effect. How ,to trouble shoot problem?
Going to go to my mehanic tomorrow . He seems not to want to deal it . We cleaned heater core no effect . He doesn't want to replace it. Ssys look for another 4 runner
l need new hester.valve seen replacements from $ 16 ,,$35 ,( ftom car parts .com ,or $60 from o' Reillys?
I really need get this trouble shooted Any suggestions ,?

 

Does the rear heating work? If it doesn't you might need a new thermostat. If it does and your mechanic bypassed the valve, the cable is the least of your worry.

I'd confirm that the heater core isn't clogged before looking into why the cable isn't working, because the heater core is the most difficult part in the interior to replace by far.

Check that the hose going into the interior is warm, then check that the return hose is also warm (when the engine is warm and the heat is on). If one is warm it might be clogged (the return line being slightly less warm than the entrance hose is normal, it shouldn't be cold). You can try doing a flush like this video, ensure the system is properly bled.

https://www.youtube.com/watch?v=YAAXSOWYKKE

 

Blend door?

 

You can try flushing the core with the garden hose. Just push the hose against the core tubing as best you can and wrap it tight with a rag. Water should flow through readily. Or get fancy with something like this:
https://www.google.com/search?q=car...783781980579527,pvt:hg,pvo:19&oshop=apv&pvs=0

Edit: so what I described is pretty much what's in the video. Guess I should have watched first...