No Hot Water from Mixing Valve
 

Delta unit is 2years old and no longer dispenses warm/hot water. Shower rarely used and was shocked when guests said the shower was cold. Ran it for 10 minutes and no hot water was provided. Similar unit in another shower so we know how it should operate. Sink faucet functions correctly. Any suggestions
to avoid calling a plumber?

Pull cartridge out and soak it in some vinegar. Turn off water before starting.

I had a leaking problem with a Delta faucet. Called home warranty, they said these have a lifetime warranty. Home warranty can give you the exact model number, Delta phone number is 1-800-345-3358, or Faucet Parts & Repair Kits : Delta Faucet (I think).

Hope this helps.