DSI Fault......
That has nothing to do with furnace --- it is a Fault Indicator for the Water Heater
Water Heater makes 3x to light off/PROVE it lit. After 3rd failed attempt to establish a flame it locks out and throws the DSI Fault Light so Owner has a visual indication that water heater failed
Furnace not firing up and running..simialr
3X to light flame/prove it light and then lockout with a ERROR code on the furnace CIRCUIT Board
RED Solid....Internal board failure
1X Flashing .....Limit switch/Airflow (fan not running/sail switch not closing/overheating)
2X Flashing .....Flame Sensing Fault (flame lit but failed to PROVE -electrode/ground issue)
3X Flashing .....Ignition Lockout (flame didn't light...gas valve/DC power)
Stove top burners......turn all on HIGH
Are Flames BLUE and same height...stay same height as you light others burners?
Let run.........
LP Reg has to have demand and establish flow when turning system on after period of non use
Cylinders OPD valves should be SLOWLY opened when first valving in for service
*Crack OPD open and listen for CLICK...then shortly afterwards should hear 2nd CLICK (That is the Excess Flow Device Inside the ACME Nut tripping and then resetting)
After second CLICK fully open the OPD
Water heater/furnace/fridge all have flame proving circuits and WILL require several start attempts to fully establish propane flow to each one of them
Stove top burners is easy due to NO flame proving used...open burner knop and light the flame.....piezo/lighter/electronic spark