Hot water pipe air lock? All aspects of plumbing questions and answers, help, tips and information

[Kaaskop]

we installed a shower downstairs and it worked for a while but now no hot water comes out.
We tapped into both hot and cold copper pipes from sink only 2 meters away and it still has hot water and cold.
Shower has one lever which is supposed to make water hotter as you turn it further. Cold comes out great but slows down and finally stops as I tunn toward hot setting.
Took cartridge out and with waters on it only come out one of two holes so it is someting stopping hot from reaching this far.
Must be air lock and with all copper pipe and most of it behind shower stall what can I do?

[thedoctor]

See our projects section as advised. Curing an air lock

[bobplum]

if cold is coming out only, i would assume there is no air lock
is the cold water mains pressure and the hot tank fed if so the cold pressure could be forcing the hot back
when you turn on the mixer you allow the hot water in and control the temperature with the cold so if colds coming out and no hot it may be pushing it back?

[bobplum]

isolate water supply disconnect the shower control exposing the piping turn water on ,catch it in a bucket (probarly a two person job)this will force the air out then reassemble and try a again