Modern Vespa

My brake light is constantly on. In addition I am able to start my gts300 without applying the brake which I believe it shouldn't normally do.

The bike runs and stops fine otherwise and there are no warning lights.

Any ideas?

It'll be a micro switch on one of the brake levers that isn't breaking the contact when the brakes are in the off position. Either the switch is bad or the levers aren't resetting to the proper position after being activated. Take the wires off and do a continuity test, circuit should be completed when the lever is pulled and broken when released. You can also push both levers forward as far as you can and see if the light goes off, thats a quick way to see if its just a lever position problem.

Do you happen know where the instructions are on replacing the brake switches. I tried pushing the levers forward but no luck.

Could be a particle or dirt or something holding the switch closed.

Disconnect one at a time to see which one is activated, and likely you'll see the problem.

Where is the switch located exactly?

It's immediately adjacent to the inboard side of the brake lever - the fulcrum of the lever. That whole grey assembly in the photo above is the back housing of the switch, and the wires sticking out of it complete the circuit that energizes the brake light and enables the starter. The other side of the switch is activated by the absence of the brake lever from its resting position. In the photo you can see the brake cable, which indicates that the lever has been squeezed. Presumably the switch toggle on the side of the switch we can't see here has popped out, energizing the circuit. If that toggle is sticking (perhaps if the brake lever got bent and doesn't contact it properly), or the wires got short-circuited, the brake light and starter will be continuously activated/activatable from that side.

Inboard of the brake lever, on the brake lever assembly.

In my case the brake switch failed and I lost brake light nor could start the vespa using the left brake. Switch was $6. This thread was helpful
brake light won't shine/engine won't start

So what I am going to do is order a couple of switches. Them remove the mirrors and just do a replacement for each switch.

Would that be correct?

That is correct if you don't have a windscreen. Remember those screw on you can't just pull them out you will break them.

Luckily no windshield.

I'm figuring if that doesn't work, I'll probably have a short in the wiring somewhere. Correct?

I'd guess a wiring issue would be the 2nd most likely culprit after the switches. Juan_ORhea's post above nails it IMO.

Disconnect the wires from the switch. If the light goes out, then the switch is defective. Can even tell which switch. If the light stays on, then you have a wiring problem. Better to settle that before swapping parts.

Sometimes a little silicone lube or WD-40 on the switch plunger (the part that moves when the lever moves) is all that is needed to restore function, although it may be a temporary fix.

Thanks gents.

Got the part and it was an easy fix

Just had my GTS service at my local dealer, and they worked with the brake light switch for the same reason. Seems okay now.