87 535is Brake switch causing radio drop out

[duncan363]

When I press the brake pedal I get a momentary loss of sound from my radio speakers. Recently I had fixed a surging/rough running of the engine at steady speed by replacing spark plug wires that were clearly arcing when viewed in the dark (much thanks to the moderator who helped me on that one). The loss of audio when first depressing the brake pedal was happening before with the surging/rough running, however I was working the bigger problem first. It certainly seemed like right after I replaced the spark plug wires that the surging engine went away as well as the brake pedal/audio thing (which was a surprise).

Within a few days the brake pedal/audio thing has returned, and the surging/rough running has come back in a very mild form. I have rechecked for any spark plug arcing in the dark and the new plug wires are producing no arcing. I suspected an engine to chasis ground issue, so I verified the braided ground cable from the rear valve cover to firewall is in good shape and removed/cleaned/steel wooled surfaces and reinstalled. The multiple brown colored coded ground wires attached to the other vehicle ground near the battery all look good (no broken wires or corrosion).

Before the spark plug wire change, I also have had a weird dull clicking noise when the brakes were warm on warm days when I depressed the brake pedal. I thought it was something with the ABS as the frequency of the dull clicking noise seems like it might fit with the raised rotor tangs for the ABS system. At its worst, even without depressing the brake this dull clicking would persist when driving at low speed. Hard to tell where the noise is coming from, however it did not effect braking or cruising. This dull clicking seemed to disappear with the spark plug wire change as well, and now has also reappeared in a much milder form. It all seems connected somehow. Any help on what electrical gremlin might be at work here?

I have been thinking about replacing the brake switch as that is the common electrical device that causes the audio drop out and the dull clicking noise. Any thoughts? Sorry about the length of the description.

Today the brake light indicator went on during my drive home on the upper display (never done this before). When I pulled in my drive I kept it running and with the brake pedal depress all the brake lights were illuminated. Something is messed up with this circuit. I am replacing the brake switch at $15.