Flashers won't shut off unless battery is disconnected

[harper]

Can't stop the flashers. Have to discon the negative from the battery because the key has no effect when turned off. 89 k100rs. 35K.

[The Mighty Gryphon]

I assume you are talking about the hazard flashers.  Outside of a wiring fault the only components that control them are the flasher module and the hazard switch.

Do the turn signals work properly? 

[Laitch]

4-way hazard flasher?  Sometimes the switch won't turn on the flashers without being wiggled. I doubt if its anything major.

The flasher switch itself in the switch pad might have an internal fault. You can trace it to its plug, disconnect it there then lube it with contact cleaner or disassemble it for investigation. Or just blast it with cleaner where it is.