4 prong flasher wiring

[clivus]

I’m about to install a Tanks Meter Match to get my last series 3 fuel (petrol) sender to match my 61 SW Series 2 gauge. The Meter Match has a low fuel light alarm capability. I have a mystery green light on the dash where the low fuel would be on a diesel(I think). It’s hooked to a fourth prong on a Durite GE746 4 prong flasher unit. It’s not powered with the ignition. I’ve identified ground, 12v in and out to the flasher. I’ve found some mention of this being a warning light for a bulb being out? It that what this is? I tried a smashed bulb in an indicator lamp, but the flasher just clicked two times in fast succession and stopped.

[roverp480]

I am fairly certain the 4th terminal is trailer flasher out warning light. Does the flasher unit have something like 2x 21w + 21w on it? If so its to indicate a 3rd flasher is working ie two on the LR & one on the trailer. If one fails the extra green warning light does not flash.

[clivus]

I should have included a better picture of the flasher, but I was having some trouble posting photos. They were all getting rotated. Thank you for your help

[roverp480]

I see it states 2 or 3 x 2? so I expect the 4th terminal is the extra warning light for trailer turn signal.