There are 2 lights for the DSI water heater...everyone seems to assume your actual switch does light up when you turn it on. Did the WH light?
If you want to see if the "fault" light comes on, turn off propane and turn on gas WH. I forgot to open tank...light came on due to a failure on lighting. It will come on after 3 (I think) attempts to light.
Occasionally, whether gas or elec., water may discharge from PRV. Sometimes, ours drips when WH shuts off after heating.
(P.S. I also am a "Fasteddy").