Hi, this is a little different to other problems on here!
Recently our shower will not get hot, it will only get hot if we run the water in the sink to hot, then we can turn the sink tap off and have a hot shower. `it is about 5 year old. Please help us!!
Thank you ,
Jules

I think you need to open up your mixing valve and clean out debris from the inlet ports. Do you know how to disassemble the valve? If you need further help a brand/model would help. Most, you start by removing the handle and the escutcheon plate.