Central Warning Light problem

[on air]

Hi all

I've got an '81 928 with 36k original miles. 5 speed manual.

When I turn the key in the ignition, all the warning light systems light up in the cluster as normal, And in the middle of the console the ! light/button is lit as usual.

When the car starts, the parking and stop lamps indicator is still lit (as normal) I take off the parking brake - its light clears, depress the brake pedal to clear the stop lamp and it clears ... all normal.... but recently I noticed the ! in the center console is still lit solid -with no indication of why it is lit (none of the corresponding info lights in the cluster pod light up that would normally tell you what the issue is)-- when I press the ! light/button it, it goes out, sometimes it will come back on within a few seconds so I press it again and then it goes out, and doesn't come on again until I start the car up the next time.

All the dash warning lights are in the pod are working (none burnt out), I've checked all the fluids and they seem fine....

any ideas what could cause this?

[Mrmerlin]

low oil level sensor or the low coolant level sensor, or low washer fluid sensor