I have a weird one that I’ve searched and can’t find anything like it.

The volume toggle on the dash works fine for about 5 minutes after the ignition is turned on. After that, the up movement sometimes lowers the volume instead of raising it.

This isn’t the strange part. Today I was experimenting with it and consistently found that when the headlights were on, the up toggle made the volume go down, BUT when I turned them off, it worked as normal.

I first suspected it was a bad switch, but now I’m very confused.

Any ideas?

 

What radio? What year car?

-- Chuck

 

MY00. Stock radio.

 

Weird electrical stuff, initial go to is always checking for a bad ground. Which is easy to say, do not so much.

Find a wiring diagram, look for all grounds related to dash, and headlights. Then physically locate them on car, and if that wasn't hard enough, get in there and remove ground bolt, clean all terminals, then scuff them up with like a scotchbrite pad, then apply a light coat of grease so they don't corrode again.

People recommend using a dielectric grease, which means non conductive. This never made sense to me. The only ground contact then is where the clamping force displaced the grease. I'd rather use something conductive.

Anyway, clean grounds with new grease will be better than dry, corroded grounds, regardless of what is used.

While symptoms sound like a ground under dash, I would think that environment would keep it clean and dry enough to never have a problem. Unless car was once in a flood, or had a leaking roof or bad heater core than got things wet inside for a while.

There are grounds on front of fenders, accessible from under hood. Easy to imagine these are used for headlights (just guessing). They always get nasty. Might be an easy place to start.

Next would be a main ground I know of under drivers side dash. I recall when doing my aftermarket stereo and other stuff, I needed to ground stuff under dash, and found a stock one right near fuse panel, so added my grounds to that.

 

I would have a hard time believing it’s a bad ground. The engine bay and interior are spotless and I’m not sure the car itself has ever been driven in the rain.

A few things that popped to mind from your recommendation:

1. I had some condensation in the left headlight after washing it. Maybe some corrosion in there?
2. I had a Bluetooth adapter plugged into the CD changer port on the stock radio. Maybe that caused some kind of interference? I did test with it unplugged and the same thing happened.

in the meantime I’ll take a look at the grounds I’m able to locate.

 

I'm not saying it has to be a ground issue, just that weird electrical issues, first thought is always ground. Normal path back to ground impeded, so electricity seeks other paths, weird stuff results.

I doubt issue is radio itself. I feel like issue is signal going to radio, not radio itself. So after grounds, I'd be thinking issue with dash switch.

Come to think of it, when headlights on, backlights on dash controls are on. I'm thinking more and more its issue inside dash control. Possibly fixable with contact cleaner spray, if you can get it inside switch contacts.

Dash disassembly, followed by switch replacement or switch dissassembly and internal cleaning with contact cleaner.

 

Makes sense. I’m waiting on delivery of a Modifry DCI so I’m going to install that first just to rule out the radio first because it’s easier than disassembling the console. Assuming that doesn’t fix it, I’ll take it apart and clean it.

Thanks for the guidance! I’ll update the thread when I know more.

 

Modifry's Tech Page explains how the Dash Switch works and how to test it if you have a multimeter and
some understanding of electronics.