I have an 83, owned it about a month or so. Mechanically everything is good, runs fine, daily driven, so on and so forth. However, I do believe there is an electrical issue.
If this isn't a problem, going to feel like a dummy. Here goes...

Symptoms:
ACC position in ignition switch doesn't work.
When switched to ON, the parking and marker lights come on all the way around.
When the lights switch on the column is set to parking lights, the radio turns on without the key in the ignition.
Oddly enough, with the vehicle running, if you switch the parking light switch on, it raises the operating voltage closer to normal (increase of about .20 V).

I'm guessing the previous owner could have changed wiring somewhere to circumvent the inoperable ACC position, but haven't found anything that looks untowards yet.
I've spent some time chasing wires and cleaning grounds wherever I've found them, but don't believe I've hit them all. Any suggestions would be appreciated!

 

Check the connections around the radio. We had a friends dash apart once and after we put everything back together, it did the same thing. As soon as the key is moved to acc or on, the parking lights come on. And there was no way to shut them off. We havent really had a chance to chase it down yet to solve it.

 

hummm,
sounds like the acc wire to power the stereo is connected to a dash light circuit, thus powering the park lights. just a thought. I love wiring stuff, but some times can be really challenging.
Does the car have an aftermarket stereo? If so start there.

 

Sounds like someone wired the aftermarket stereo wrong. For 84-85 there are three plugs for the audio system behind the decks in the dash.

J-05 is a single female spade, with Blue/yellow wire, that always has 12V. Could be continuous power for stereo.

J-04 is the a six pin female spade connector with only 4 terminals used. Blue/yellow has constant 12V. This is the one I use for constant stereo power. Blue/white is 12V switched from ACC. Should be switched power for stereo. Red/green is switched 12V from Combo (light) switch for illumination light in stereo. Blue is connected to the terminal with the blue wire in Plug J-03.

Plug J-03 is a three pin female spade connector. Red/green is switched 12V from Combo (light) switch. Blue has switched 12V from ACC only if Blue/white wire is connected to the Blue wire in Plug J-04. Blue/green wire is the 12V power trigger (for ant. or amps) to the power ant. relay from the stereo. This terminal won't work if the power ant. wiring is stock. Mazda uses a negative trigger to raise and lower the power ant. Almost all decks use a positive trigger, so custom wiring is needed to make the ant. work.

Sounds like one of the Red/green wires is connected to switched 12v from ignition switch. The 12V would then run backwards to power the other lights powered by the Red/green wire. That would be parking, marker, etc. If Red/green wire is used to power stereo the light switch would turn it on. Maybe the red/green wire is crossed with one of the Blue/white wires?

 

Well, it has an aftermarket radio. I can't get at it tonight, but will give these ideas a shot tomorrow. At least the dash is easy to get apart. Thanks for the quick response and I'll let you all know what happens.

 

Mine was doing this too, but then after I replaced the stereo with mine, it just went away. I guess that just helps confirm that it is probably a stereo hooked up wrong. BTW thanks for stealing my thread title :P

 

lol, you're welcome. At least I was specific.

Red/green was crossed with one of the blue/white. Issue is now resolved. Thanks much!

 

good job fixing it, and welcome. What part of AZ are you in??

 

Sierra Vista, this tiny little mousefart in the hills that apparently likes to burn.