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I am trying to replace the stereo in my car. The old stereo was working, but it didn't have bluetooth. So I managed to get the old one out. Cut the wires going to the harness. Then began connecting the new harness wires. All was going well. I got the power wire (yellow) connected., and tested that it was the 'hot' wire from the battery. Same for the ground (black). Then I connected the wire from the marked as 'ignition', but when I checked, there was no power on it, even when the ignition key was turned to the accessories position as well as starting the car. Still 0v in all positions. This did work when it was connected to the old harness. So I must have done something when I cut the old harness, maybe? That wire goes into a big bundle of other wires, which then goes under the dash.
I tried all of the other accessories, and they were working as they should, with the key in all positions. I thought about connecting a wire directly from the key switch. But I didn't know what voltage it was, and whether there should be fuse, or something else between it and the stereo harness.
I had my mechanic look at it. But he said it was going to be a big job to trace that wire, since it meant taking apart the dash. And I didn't want to take it to any stereo install shop, basically for the same reason: I really didn't want some kid hacking around who probably had never seen a car this old. I do have the original shop service manual for this car, but following the wiring tracing is a bit beyond my skill set (okay, I am an electrical engineer, but those wiring diagrams are nothing like I'd seen in school ).
Driving around without music can't get real boring, and, also, I just might miss that one important call .
Did you locate and check both fuses? There should be a 2-amp inline fuse in the console, roughly in the area beneath the LH ashtray. The diagrams also show a 20 amp inline fuse behind the dash, in the area of the RH component panel below the glove box.
According to my diagrams, yellow is key-on power and red is constant voltage for the radio memory.
The key-on power comes via the radio relay....which is located in the console just aft of the gearshift.
At the relay:
Terminal 86 white/pink 12v with key on
Terminal 85 ground
Terminal 87 yellow output to radio
Terminal 30 brown and red brown is 12v constant from battery, red goes to radio
Here's a visual of the information Doug has given you. Just below orange vac tube and grey wire you can just see the end of inline 20a fuse in N Radio relay is small silver box just below shift cable and 2a fuse is tucked in below fiber optics above shifter. wire.
If your car is an original car then by all means follow the guidance above and do it right. If it has been modified just run new 12v and ground wires to the new radio and insulate all of the unused wires so you don't get a short.. I had a 1949 Chevrolet that I always ran new lines in until I had the whole car rewired. Be sure to use the proper sized and quality fuses.
You may want to run a new (fused) lead from the battery as Yellow series 3 suggests, for another reason too. If you are installing a high-power head unit, you'll need a larger gauge wire anyway to handle the current, or the amp will cut our when you turn up the volume.
There's a grommet on the firewall you can put the wire through (photo).
Looking at going to the original fuses means taking apart a lot of things (dash panel, etc.). Not something I'm really up to, and probably the reason my mechanic didn't want to get involved with. I had, though, considered running a new wire to the unit.
Below is from the unit's manual:
I have the yellow (battery wire) with 12v, and black (ground). It is the red (ignition wire) that has no power, even when the key is turned, or the car is running.
Just in case, I do know the unit works, as it has been tested with a working harness in another car. Also, if I just use the 12v battery wire for the ignition wire, it does work. But that would make the unit pull power from the battery all the time, and probably drain it.
Last edited by daytooner; Mar 2, 2022 at 11:51 AM.
daytooner, I won't try to dissuade you adding another wire, but getting to the 2a fuse and the relay can be done by removing one screw above the window switches and lifting the console top plate out. 20a fuse can be accessed by removing two screws through plastic vent in right side of transmission tunnel. Push forward slightly and lift small side panel away from tunnel. Fuse is as shown in my picture #1. Pretty easy.
Dave
P.S. The 2a fuse will be the ignition/hot wire to the radio.
Unfortunately, I have been side tracked by other (more important?) issues. But I am trying as @LT1 jaguar suggested. The car is mostly original, but it can be fragile and a bit fussy.
Stereo wiring problem
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