Sounds like something is feeding back from the running light circuit into the brake light circuit. A buddy of mine had this on his wife's Honda Pilot.... the cruise control wouldn't work when the headlights were on. Went out back and started looking at all of the bulbs and we saw one of the dual filament bulbs had failed in such a way that the filaments were touching each other. When the headlights were turned on, the power was diverted into the brake light circuit and the system thought you were pressing on the brake pedal and kill the cruise control. I'd look for corroded sockets and bulbs, and maybe even mismatched bulbs. I've seen on another Honda where someone crammed a dual filament bulb into a single filament socket.... every time you'd used the turned signals it would feed power into ground and the radio would turn off and on with each flash of the signals.

 

Wow! Just dipped back into this thread and holy cow that's a forensic analysis. I didn't even know that the filaments could do that.

 

[UPDATE] 3 months and no return of the 3 amigos!!! must have been something with battery!?

 

Thanks for following up. When the thread popped up I thought "holy cow I've heard of that problem before!" But it was you. Congratulations on solving it.

 

haha yeah RPITA! has been plaguing me for 4 years lol I checked all the grounds but nothing was out of sorts... added dielectric grease to all connectors I could find... and in the end much have been 2 bad batteries in a row but this new OPTIMO Red is working great!

 

I've gotta admit DP that's a first in my experience of problems, it's unique

I am certainly not into auto electrics but those problems seem exceptional. Good you've sorted it though.