Well, your first problem is that the Ford Focus wasn't made until 2000. Maybe you have a different car altogether.
As far as I know , the multi-function switch is the switch for your turn signals , flash to pass , hazard lights etc . It is inside the steering column
if you mean: "why do hazard lights flash when brakes are on", then the answer is because vehicles are equipped with a hazard light relay that supercedes the brake lights. This way, slow moving vehicles can operate under hazard lighting.
To make the hazard lights alternating flash, a kit called a wig wag is added to the flasher system. To have actual strobe lights, then a strobe kit with its own light has to be installed.
it may be a loose connection on the back lights give a good firm push on the connectors
what car have you got?
Does your hazard lights only work when you turn the flashers on and the turn signal on at the same time? GM is known for having a multi-purpose switch... this switch controls your lights, turn signals, hazard lights and high beams... sometimes cruise control too... well anywho, sometimes that switch is partially broken... I recommend hooking a multi-meter to the wires that hook the multi-switch up and test all the functions of the switch... but I guarantee if you put a new multi-switch on the car that your hazards lights will function properly... I also recommend buying the part through an after-market company because it is cheaper...
you have a short to ground . have it check soon ! could be a door switch .
There is a short in the wires in the turn signal circuit. The combination switch in the steering column is a good place to check. Do the hazard lights still flash?
If this occurs under heavy braking (i.e. ABS has kicked in), then the hazard lights will start flashing. They will turn themselves off after a few seconds of normal driving. If it occurs whilst generally driving along, it could be a bad connection in the hazard light switch, or something more technical inside the car itself.
The turn signals and hazard lights on this year Beetle are controlled by the hazard switch. Dealers refer to this switch as a hazard/flasher module. When the switch fails, the lights typically flash once or twice then stop due too faulty internal contacts. The switch/module is just like the old style turn signal flasher that older cars used years ago, only the cost is a little bit more expensive. This is a common part that fails on this vehicle.
Bad connection somewhere, switch, relay or ground.
Replace the turn signal flasher relay.