Fire Warning Test B733/4 vs B738
 

I have a question which is driving me nuts.

When conducting the engine/apu fire warning test on the B737-300 and 400, the fire warning lights on the glareshield and the fire warning handles on the centre pedestal illuminate together.

On the B737-800 the fire warning lights on the glareshield seem to light up approximately 1-1.5 seconds before the fire warning handles on the centre pedestal.

I know it is not much but it is definitely a noticeable difference, generally because I cancel the warning and then have to do it again when it is set off a second time by the fire warning handles.

Does anyone know the difference in the warning system that causes this?

Are you sure you're not getting the first warning on the glareshield panel from the Overheat detection, the second from the Fire detection?

Are you sure that an overheat will trigger the fire cue ?