intermittent light issue

have you tried adding brake fluid? I had a problem like that... adding fluid stopped it. There was another thread on here recently where someone had a problem with the brake switch.

 

I'd put the highest probability on a fuseblock problem. There are three wires hooked to the tops of fuses #1, #2, and #3 that should all be well-connected together electrically (by the straps/rivets on the back of the fuseblock itself), and they should all be at the same voltage when the engine is running and when you step on the brake pedal. Sometimes these wires get switched around inadvertently, but the way it should be is:

+12V power comes into the top of fuse #2 on the large A (light blue) wire;

this gets bridged over to the top of fuse #1 and exits out the top on the G (yellow) wire to run the ignition system (and current flowing down thru fuse #1 runs the brake lights);

the +12V power coming in on the A wire also gets bridged over to the top of fuse #3 and exits on a GN (yellow/black) wire and goes to one side of the alt. "G" warning light.

If the straps/rivets are not well-connected electrically (i.e. they have a small resistance), this can cause the voltage to drop when a large current is flowing (i.e., when you activate the brake lights).

Measure the voltage on the GN wire and the A wire (both relative to chassis ground) with the engine running both with the brake lights on and off -- if the voltage on the GN wire "droops" below the voltage on the A wire when the brake lights are "on", this is the problem.

If your alt "G" warning light also flashes with the turn signal lights (or anything else that draws large current from fuse #1) this would be another indication that this is the source of the problem.

Good hunting -- let us know what you find...

 

I am not an expert, but I thought I would post because not many have responded to your question. Those who know more please correct anything I get wrong.

Sounds like a short to ground. The red light is your alternator light (G for Generator I think). Sounds like that when you hit your brakes, a short circuit path is created making the indicator read less than normal amps. If you need a procedure for troubleshooting this send me a note. There are others on this site much more electircally oriented that I that may have other ideas.

Another thought. What is your RPM when this happens. My alternator light begins to flicker when the RPMs drop below about 1000 indicated (about 700 actual).

As friendly advice, determine the cause (or causes) of the problem before you start changing parts. The fuse block may be the cause of the problem but verify this before changing it. Even if it is not the cause you may choose to change this anyway. You need to be able to reproduce the problem at will before you know you have it.

 

Even if that isn't your problem (and the turn signals not causing the same situation is a sign it's not), making a good reliable connection between the tops of fuses #1, 2, and 3 is always a good idea IMO. I soldered some busbar across the base of the three male tabs pointing upward, and others have reported soldering the plates and rivets directly (although in both cases it's not easy to get enough heat to melt the solder without hurting the plastic).
If it is just an alternator current capacity problem, I'd have guessed that turning on any high current gizmo (like the headlights) would cause the same result -- does it?