Weird Electrical Gremlins

[hutch]

Soooo another stupid question from me

I reinstalled a radio into my SPG so I could actually listen to music again, having a similar issue to what I had experienced before.

Symptoms:
1) Radio only outputs to the LF speaker unless....
2) When turning the car off and when the key is in the very first position the RF and LR/RR speakers kick on
3) When #2 happens the radio will stay on until I cycle through the key positions again and eventually shut off.
4) When this happened before hitting the turn signal or brake lights would clear something up and the other speakers would work. When doing #3 now I can see the VDO gauges flash a bit when I hit the turn signals as if there is some errant power making there way around (gauges are powered by radio harness)

My thoughts are a bad ground somewhere, or maybe even something as random as a bad bulb somewhere but figured I'd see if anyone had any wild ideas before I try anything stupid. Only other thing I can think of is if I somehow switched the constant and switched 12v but I can't reason why/how that would work, and why the LF speaker still works regardless

[Crazyswede]

Check to make sure all the connectors on the ignition switch are clean and on tight. I've experienced some odd electrical behavior due to loose connectors down there....and in one case a dime had worked its way down to the switch and would roll back and forth making odd contact with terminals and cause issues.

I seem to remember that my 85 900 has issues with the radio also behaving strangely with the turn signals and maybe on right turns.

[Geoff]

I've seen a few C900s where strange things would happen when the wrong bulbs (reverse, brake, turn signal, etc.) were used. Strange things like the headlights would only come on when the turn signal was on or the reverse lights would come on when the brakes were applied.

[hutch]

Yeah I was thinking of popping off the center console and jiggling the connectors as it seems odd that it magically fixes itself when the key is all the way to the left and then goes away.

And definitely plan to swap some bulbs around as I had heard similar tales of wrong ones causing all sorts of odd issues like this. I did find another oddity as the orange corner lights don't light up, unless the turn signal is on, so something definitely seems to be pointing in that direction...

I'll keep you posted if I find an answer!

[DrewP]

I do not envy you. Mine does all kinds of weird things when it's really rainy, especially with the central locking actuators and the wipers. Since I live somewhere that's very dry, I have not had motivation to investigate further.

I mostly saw weird things with the wrong bulbs in the sedan/convertible rear lamp assemblies, but there's no way to predict when weird things like that start to happen.

Did you put in an OEM radio, or an aftermarket one? Might be worth it to just add a fresh new ground lead directly to the chassis somewhere to the ground lead going into the radio head unit, in case it's just getting that interference from somewhere. It's weird that the speakers selectively stop working, since those are powered directly by the head unit and don't ground anywhere directly to the car?

[hutch]

Yeah I've only really noticed it as I've been DD'ing the SPG recently and never bothered dealing with it before (usually prefer just to listen to c900 burble) and rarely drove it at night as the headlights suck so never really noticed the corner light thing.

This is an aftermarket radio, and I was thinking the same with the ground strap as there is a lug on the back that I assume is for that purpose, and it can't hurt. But yeah the selective speakers is just so weird as that suggest its internal to the head unit itself I'd think? But since the other speakers can work that makes me think its something weird going on with power or ground making its way to the radio

[Crazyswede]

Lets not forget the rear light assemblies in the 4 door/notch/convertibles which were prone to corrosion and cross voltage contamination