I'm replacing the radio in my 71' 240z and wanted to know if anyone was aware of any wiring limitations. I've already read about the issues of upgrading the lights and melting the fuse box and didn't want to do the same with the radio.

I'm looking at one that puts out 25 watts rms/ 45 watts max x 4. Any ideas?

 

Welcome to ZDriver.

Wire in a new 12v+ power supply like you should, and then you won't have to worry.

 

Check out a free '72 factory service manual at XenonS30. Xenon is looking for the '71 edition still.

45 watts isn't a lot for ordinary 'speaker wire' they sell at parts stores. Lamp cord is cheaper in bulk and has even more copper. Your call. Not to worry about melting anything.

 

Yeah, I didn't think it was that much power, but thought I would check just in case. Thanks for the advice.

 

When you're worrying about melting the fuse box, it would be the +12V line you're concerned with. That circuit is protected by a 10A fuse which works out to a 120W draw. Your speaker output at 45W isn't the same thing as the receiver's power draw as its circuitry will consume more than just the 45W output. It's probably more like 90W but that's just a guess. If you can find the actual power draw of your system, that's what will tell you if you can use the existing radio power circuit or if you need to run your own separate fused wiring from the battery. Sometimes the +12V line on radios will have their own fuse. If that's a 10A or less, you should be good to go using the existing +12V circuit.

 

To guard against adversely affecting 40 year old wiring, do as Nismopick suggests.
1. Run a 14 AWG wire from the positive side of your battery. Have a 10 A fuse in the circuit. If you think you might want a more powerful stereo someday, run a 10 AWG wire instead with a 20 A fuse.
2. Connect that wire to the 87 pin of a relay. Connect the 30 pin of the relay to the switched power of the stereo.
3. Connect the 86 pin of the relay to the existing switched radio power in the wiring harness and connect the 85 pin to ground.
4. You can tap into the cigarette lighter circuit for the unswitched (memory) circuit of the radio.

 

You know Steve, I have to say thanks to you and Nismopick for those posts. As I'm going through my own 260 (which completely blasted apart as I'm touching every part), I didn't consider adding a separate switched power circuit as there was already so much on my plate and I'm not expecting to install a super high power kick-you-in-the-butt sound system. However, now that you've laid out the details it seems very easy, easier for me since everything is wide open right now. I've even got extra relays and wire in my parts bin. Might as well do it now.

Seem like adding some USB power outlets, hidden in the ash tray or the console might also be useful.