I have a 19mm Master Cylinder on my car but I believe that the mechanic reused the sensor switch from the leaking 17mm MC that it replaced. The warning light has been blinking. The light was not blinking with the small leak that I had with the 17mm. I'm hoping that the sensor switch just needs to be reset.

How do I reset the 17mm?
Does the 17mm switch work with the 19mm MC?

Thanks as always!

Did you reach in there and push the button on the sensor? It should be under the rubber black nipple.

I see the button on the 19mm sensor but the thing on the 17mm doesn't look like a button and doesn't seem to want to push in??? Maybe I'm just being to cautious.

I have a 19mm master cylinder and the button is inside the black rubber cover. I just push down on the rubber cover to reset it. Can't remember what the 17mm looks like. It's been to long since the switchover.

The unit with a single connection has a reset switch. The two connection unit doesn't. You can pull the switch without affecting the brake bleed (always use caution the first time out though, your e-brake works, right?). Pull out and manually operate the switch to make sure it works. If it does, look inside where it goes, there is a little plunger that moves forward-backward. Make sure the thin section is in the middle. If it's not, use something small (a punch?) to move the plunger back into place and reinstall the switch.

Thank you sir, I'll give it a try!