Brake light progressively gets brighter (1 Viewer)

[F226continental]

Since 1993 my fj60 the brake light (right under the tach) has been on. It was barely visible in daylight for 10 plus years, then just kept getting increasingly brighter. Now it is about 3/4 of a full 12v brightness. How I judged that is when I pull up the parking brake it still gets a little bit brighter.

I haven’t driven the truck since 2019 but have been getting it back in running condition in the last couple weeks. The brakes are in good shape, and work fine.

What’s the problem fella’s?

 

[F226continental]

At first I thought I might have a vacuum issue, but no sensor I can see on engine vacuum exists. And booster works great

Fluid level sensor on master cylinder cap gone bad?

 

[cruisermatt]

Voltage regulator on it’s way out

 

[F226continental]

Voltage regulator on it’s way out

External Regulator?

 

[OSS]

The brake warning light grounds through a common ground connection behind the instrument panel. All the dash warning lights do - along with some accessories — namely the headlights.
If that connector (ground bus) overheats due to excessive current (from high wattage headlights) the high current overheats the connection, stuff smokes, and the spade connectors can lose electrical connectivity.

When this happens, and the normal path to ground is impeded, a circuit running through that bus connection will find the path to s ground with the least resistance — in your case, possibly through the brake warning bulb to ground.
You may have a “floating ground”.
It’s very common in these vehicles.

My advice — remove the instrument panel and look for the ground connection bus thingy/ it’s tucked behind the wiring harness, and examine it closely for any evidence of overheating.
It has a bunch of black/white and blue striped wires going into it.

 

[F226continental]

Hmm, that sounds very plausible, especially since it has taken some time to get worse.

 

[F226continental]

Well after removing gauges, the 3 ground wiring buses looked brand new, no corrosion at all. The wiring system in general is in pristine condition, truck has always been in garage when not in use.

ill check out the voltage regulator next

 

[CJF]

Fluid level sensor on master cylinder cap gone bad?

Unplug it. If the light goes out, that's your problem.

 

[F226continental]

unplugged brake fluid level sensor and no change

 

[F226continental]

Ordered a NOS voltage regulator from vintageteq, maybe that will fix it.

Send me a good one Matt!

I have doubts about it working, but won’t hurt to have a spare

 

[diesellibrarian]

I just went through this too. Tried everything I could think of, including swapping in two different alternators (FJ62s have an internal voltage regulator). Tested and re-tested the master cylinder reservoir cap, hand brake switch, various relays, etc.

In the end, I removed the bulb, and lo and behold, it hasn't come on since!

 

[F226continental]

LOL, that’s basically what I did after checking stuff today. I just unplugged the bulb and harness from the brake light. I can still see light from behind the cluster, but it’s a lot less annoying