Quote,
From page 68 of my 69 GMC Owner's manual A light flashes to indicate proper operation of the front and rear turn signal lamps. If the indicator lamp remains on and does not flash, check for a defective signal lamp bulb. If the indicator fails to light (((when the lever is moved))), check the fuse, and indicator bulb.
Is this all it says? because this states what I said above about "you apply the blinker and it stays on" does your book say anything about the park or headlights being on? turn sig and brake lights are on a seperate circuit than the park and only share a duel filement bulb.
The reason the the indicater light stays on when a bulb is out is the flasher(coil wrapped around a bimetal strip that heats and warps to open a set of points) is in series with the blinker circuit, when a bulb is out there is not enough current draw to heat the flasher to open the circuit thus not flashing and keeping the light on.
The reason a ground will do a similar only when the lights or on is a duel filement bulb has two leads that share a common ground, when power is applied to either or both the currents least resistance is to go though the filement and to ground, but if ground is lost then it will travel through the other filement to get to ground(this is why one headlight will be dimmer when it loses its ground it is going though both filements (hi-lo) to get to ground)
but on a park light it will travel though the blinker filement and to the indecater bulbs that are grounded making them glow or flicker.
This is not a Pi$$ing contest and I am not trying to offend just being helpful.
