the check light comes on flashig but the brake ligths are working how can l stop this .

Clean the bulb sockets of any rust. Use bulbs with stainless steel bases, not the brass stuff. The bulbs may still light but the path to ground is weak and looks more like an open circuit to the computer.

Does the flashing light continue to flash after u drive off
or does it light up only at start up ?
The check control unit of older cars usually illuminate the brakes at startup (which is normal procedure, for it is only trying to monitor the said item). After stepping on the brakes & moving off, the light goes away.
And ur statement is really unclear. You failed to mention that the flashing lights r about the brake lights which u proceed to say r working.

It is supposed to flash on the instrument cluster & the led on the control board will light up. It is supposed to go away when u step on the brakes. It is their way of testing if it works. If u steap on the brakes & it still does not go away. Make sure u have the right bulbs back there because a higher or lower wattage will through off the computer. If everything checks out & the warning lights still do not go away do this.
these r procedes from R3Vlimited.

Here is what to do first: Go buy a can of CRC ''Electrical Contact Cleaner'' & perhaps a couple of Q tips, & a nice new pencil eraser. Maybe have a bit of sctochbrite & some of the red shit u spray on ur battery to prevent corrosion ( l do not use that shit, BMW didn't) if u want to see if that stuff makes ur connections stay good more than 15 years.

Now, Find the ''rear lights check relay it is a small black box, about 3'' X 2'' X 4'' with a few wires coming off its ass end. It is under the same panel as the antenna & the amplifier, AKA left trunk liner. Unbolt it & BOTH taillights, unplug all 3 & place them on a workbench or something, or piss off Mom & use the kitchen table.

Now, take a close look at the connectors in the car. Spray them heavily with CRC. Use Qtips, scotchbrite, whatever the hell u ave to scrub the connections down in the plug.then spray again.get them all nice & shiny clean. l think l used a toothbrush on mine.

Cleaning the rear lights check relay is really simple, just scrub the contacts with a pencil eraser, then douche with CRC. They clean up aesily.

Now, on to ur taillights. Take the backing off of the lense, & if u want to ''never deal with this stupid check panel light again'' (like me) pull the bulbs out one at a time, & scrub the holes with Scotchbrite & CRC, until the bastards look NEW. Make sure u clean the point where the ground is attached, too.that one plate grounds the whole plate, make it perfect.

Now, reassemble car, with or without new bulbs.clean the bulbs if u r reusing them, though. While reassembling, make sure u r using the correct bulbs (NOT 1157s). Check to make sure every single connection is nice & tight. You can use a metal pick tool (which every single person on this board should own) to pull the connections tighter.whatever.just make sure every single connection is tight.

Your ''CHECK'' light should light up every time u turn the key on. As soon as u step on the brakes, that CHECK light should turn off, unless there r other issues.

''make sure you are using the correct bulbs (NOT 1157s)''

Dont you mean 1156, an 1157 wo not fit in there because of the offset prongs!!