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In theory the light should indicate when the GP's are warm enough to start the motor. As noted, they may continue to glow after motor start to help with combustion and warming the air inside the cylinder. While getting an additional light to show when the GP's have current is one way to go, and another is to just glance at the volt meter as they draw a lot of power.
From the description (and am presuming a cold start), the short 'On' time does seem suspicious to me. Waiting a few more seconds certainly will not hurt.
In practice, the amount of wait time depends on temperature (warmer = shorter). If I am starting a motor after it was shut down just a few minutes prior (example: refueling), I usually start immediately rather than wait based on the light as the motor is already at operating temperature.
I have watched mine on a cold start( first of the day, light goes out about the time my key in chime stops) so on cold morning i will wait a little longer
after it has been run up to temp It will just kinda flash, like you i will generally just fire it once shes warm
I figure that you probably pronounce "Hehkut" differently than we native english-speaking types. To me, it's pronounced like an Australian would pronounce "Haircut" (dropping the "r" and replacing with the short "a" or "eh" sound).
Not sure about the others, but my glow plugs don't even come on until the wait to start light goes off. So if you don't have a digital volt meter or LED indicator mod, don't start blindly counting seconds until after the light goes off. In the winter if you start cranking as soon as the light goes out the glow plugs are just starting to get juice and won't be hot enough to really help at all for a good 10 more seconds, which ironically is after the fuel pump times out and shuts off...
I’m gonna take a video of my dash when I can On initial start up so you guys can see exactly what I am working with.
As old as your truck is now, I'd just pull the cover and replace all the lights. Not that hard of a deal. Especially if you have so many non working lights, you can't see the instruments at night.