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Thanks, Kev.

Here is a bit more information on what’s happening. Most of the time things seem to work fine. Then, on occasion and seemingly no reason (like in the middle of the night), the brake lights will come on dimmly (sometimes brighter than other times). They were definitely off before and then just came on at some point. Now, these are LED bulbs, so it doesn’t take much to make that happen. But, the car was just sitting and cool.

Initially, I could tap the brake pedal and that would normally get the lights to turn off. The problem has gotten progressively worse and happening more often. And, tapping the brake pedal has less and less effect of turning off the lights.

I’m wondering if the diaphragm in the switch has weakened and not “springing” back to the off position as it should. It seems like that could explain the problem getting progressively worse.

I have no idea when/if the switch has ever been replaced. Anyway, that seems like the place to start.

I have new coil springs to install, and looking at the shop manual, it looks like I need to disconnect my brake lines as part of the spring removal process. I’ll likely replace the switch at the same time so I only have to bleed the system once. Then again, depending on my brother-in-law’s (mechanic) schedule for help with the springs, I may go ahead and do the switch first and then bleed the system again when we can get to the springs.

Some master cylinders are designed to keep a small residual pressure on the system to keep the cups set and prevent air intrusion. Maybe your brake light switch is too sensitive. Or maybe a small amount of current is leaking through the switch due to brake fluid getting on the contact side of the diaphragm. Brake fluid often has some moisture and fine rust in it, which could aggravate leakage.The Led lights might respond to a very low leakage current that would not affect regular filament bulbs. I'd disconnect the switch and see if the problem goes away, or replace it.

Replace the swtich. $12.99 Napa. SL-134

Or if you want screw style terminals:

The other reason for brake lights coming on by themselves is that the the master cylinder is not returning all the way to "home" and is not uncovering the compensator port. Make certain that your pedal push rod is adjusted so that you have at least 1/8" play at the pedal before the piston begins to move. You can also check very easily by grabbing the push rod and attempting to wiggle the cylinder end a bit. If it won't move, you need to have some free play adjusted in.

Thanks, Ross.

I’ll check that. I do know that everything worked fine for quite a while and it’s gotten steadily worse. I don’t think anything has changed regarding the adjustment, but it sure won’t hurt to check it before replacing the switch.

Okay…checked the adjustment. I don’t think that is the issue. I had enough play and the “wiggle” at the cylinder as described. Since it was easy, I went ahead and back it off a bit to see if it made any difference. I kept track of how much I backed it off. It did not make any difference, so I put the adjustment back where I had it.

I have a switch on hand from O’Reiley’s. I’ll either install now or wait until we are replacing the coil springs depending on my brother-in-law’s availability.

It should take all of 5 mins to change out the switch. Three of which is finding the correct wrench.

If you remove the old one and immediately replace it with the new you shouldn't have to rebleed the brakes.

Thanks, Kev. I’ll swap it out sometime over the next few days.

I got the brake light switch replaced. Problem solved. Thanks again to all. Kev- thanks for the insight that I wouldn’t need to bleed the brakes. I was just assuming that I’d lose a lot more than two drops of fluid, but clearly that isn’t the case.

Out of curiosity, I put a meter on the old switch after it was removed. It was 525 ohms, so it definitely was not opening all the way it had fluid on the contact side of the diaphragm.

Also, the 00 battery cables definitely made a difference on how the car starts. I thought it started quick and easy before, but wow…it’s quite a lot of difference.

Now, I probably don’t really need the battery disconnect switch, but I do like having it and having it a convenient location.