Im betting its your fasten safety belt buzzer. Next time you get in it the seat belt light almost goes off the same time the WTS does. There was a thread a few weeks ago about this. Id say its your safety belt buzzer as it is also tied into with your dome light.
Nail, meet head. That's exactly what it is...the simplest way to test it is to fasten your seatbelt before turning the key on. The buzzer SHOULD turn off (although the "fasten seatbelt" light should remain on)....if you don't have the seatbelt fastened, the buzzer and "fasten seatbelt" light should turn off at the same time. And, yes, I too have noticed that the seatbelt light/buzzer turned off at around the same time the glow plugs finished cycling
(I say "turned" because something failed in mine; I still get the key in switch/door open buzzer, but my seatbelt buzzer failed a few years ago).
Or the key in IGN buzzer if he has the annoying one that goes off for about 10 seconds after turning the key on.
I'm pretty sure it's the seatbelt buzzer...at least on my truck, the key in ignition buzzer doesn't turn off until you remove the key or the truck's batteries (or the buzzer module) fails
IIRC some newer trucks have a chime instead of a buzzer...I wish I knew of a way to tell the difference between the two by just looking at the module. I need the key-in-ignition warning; I've almost left the key behind too many times
(I'm more than a little bit absent-minded), but a chime would sound nicer than a buzzer...
