2000 Honda Civic Brake Light and Master Cylinder

I have a 2000 Honda Civic with 85k miles on it. In March I took it in to get the front and rear brakes done. Everything was fine until May. In May the brake light came on and the brake pedal got very very loose. I took it back and they bled the brakes saying there must have been an air bubble in the line. That fixed the problem until last week when the brake light came back on. I took it back over the weekend and they looked at it closer. Turns out one of the calipers was failing and that is how air was getting into my brake line. They replaced the calipers but the brake light is still on. They were aware of this and told me there must be a problem with the light sensor because everything else checked out fine after the repair. They said there’s plenty of fluid and nothing else is wrong. They said the only way to replace the light sensor would be to replace the master cylinder but since there is nothing wrong with the master cylinder, I shouldn’t worry about it. I believe them since I’ve been taking my cars here for a long time now but I’m still worried a bit that the light coming on might mean something other than just a faulty sensor (not to mention its annoying having it always lit up on the dash). Any ideas?

Even if what they told you is true about needing to replace the master cylinder to turn off the brake light, how would you know if an actual problem arose? How is braking action now?

Its braking fine now. The pedal is firm and I can’t feel any problems. I’m just not sure what to do.

Something doesn’t seem right. None of the replacement master cylinders I’ve looked up appears to include the brake pressure warning switch. None of the online parts places seem to carry the switch; it could be a dealer-only item.

is the same light triggered by the MC the same indicator light that lets you know your parking brake is on?

Yes. They are both the same light. But I never use the parking brake so I don’t think that would be what is causing it.

Cappy may be on to something. Cycle the parking brake handle several times to see if that fixes the problem.

And you should make a habit of using the parking brake. That will help keep it operational for when you need to keep the car from rolling on an incline. In many states, the car won’t pass inspection if the parking brake doesn’t work.

I’ve engaged and disengaged the parking brake a few times to try to get the light to go off to no avail.

Any more detail on the “failing caliper” and how it was introducing air into the system?

Let me see if I remember this right. A seal was cracked or wearing and because of the suction that is created when you press down on the brake pedal, it was drawing air into the system whenever I stepped on the brake. I’m pretty sure that’s how he explained it to me.

One thing I noticed last night is that when the brake light is constantly on, it is dimmer than the rest of the lights on the dash. If I pull up on the parking brake, the light gets very bright. When I then disengage the brake, it goes back to its dimmer state. Why would a warning light have a dimmer effect? Shouldn’t it just be on or off?