Should have one... The bypass valves are located at the water heater in most FunFinders. Most consist of a branch pipe connecting the cold inlet pipe with the hot outlet pipe and 3 "on/off" valves; one in each of the 3 above mentioned pipes. The valve handles aligned with the pipe mean "on", valve handle perpendicular to pipe is "off".
For normal water heater operation the cold handle should be aligned with the pipe, the hot handle should be aligned with the pipe and the branch pipe handle perpendicular to the pipe. That will force cold water through the water heater to be heated.
For bypass operation, cold handle should be perpendicular to the cold inlet pipe, the hot handle should be perpendicular to the hot outlet pipe and the branch (bypass pipe) should be aligned with the branch pipe. This will force incoming water (anti-freeze) through the branch (bypass) pipe, avoiding the water heater.
My 2 cents, your mileage may vary...
2 Cats; J-Lo and Ragamuffin :R
2014 Thor Tuscany 40RX DP
2011 Ram 2500 Longhorn CTD HO
2011 Keystone Cougar 318SAB (now gone)
2008 FunFinder X 210WBS (Sadly gone)