Does this unit use a diode for the water valves ?

Hello
The diodes are embedded in a small portion of the harness between cluster of solenoid valves. The harness section has the diodes placed in the proper direction for current flow and covered with heat shrink material to help with corrosion and such. If ones has the experience with replacing these types of electronic devices, there is nothing to stop one from doing just that. Most appliance services are not used to replacing individual electronic components so that’s why the harness section.