My wiring diagram doesnt have the radio circuit at all and i dont have a factory radio, not sure if the car ever had one, i assume yes since i have an antenna. Im installing an aftermarket car stereo and would like to use the fuse designated as "radio" but dont know what wire to get the power from in my harness to use this fuse. I see no extra plugs under the dash that would have been for a radio

Second choice would be to use the heater/ac fuse as i dont have either. However i used a meter on all the wires on the heater control plug and the only one with power is the brown one but it has it with or without the heater fuse in.... I cant find what wire is fused for this circuit either.

thanks

The radio is powered with a 20 ga. yellow wire. The fuse is on the right side of the fuse panel in the center, 10 amp I think.

Thanks! Where might i find this yellow wire in the harness? Does it join up with other wires somewhere? As i said, i see no plug that would have gone in a radio, perhaps thats a seperate harness that was removed? I located the fuse, i think it was the 2nd or 3rd from the bottom on the right. I tried using a fuse-tap but that didnt work and just ended up breaking the fuse. That is when i decided it was best to use the factory wire if i can find it.

On 69 radio power is a 20ga Yellow wire off the fuse panel according to the GM Service Manual I have - can't tell you if it's the same on a 68. The manual doesn't show any plugs in between so I would look at the big loom coming off the panel and follow it to see if you can find where it comes out - or pull back some tape and see if you can find it in there.

1968 also use a 20ga Yellow wire.
RPO U57-A5, Item 8, main view and also view B.. "Power lead from body harness (Yellow wire)"

One would assume that this wire is in all standard looms, but like yourself, I can't see any yellow wire in the UPC 12-D2-3 diagram.

The U57 main diagram shows it hanging down at the harness support clip, that is closest to the instrument panel.
It's very possible that this wire has been cut off in the last 40 years as stereos come and go as frequently as owners and boy, I've seen the mess backyard stereo installers can make!

If you can access the loom near that clip, perhaps try removing some tape to hopefully reveal the end of that yellow wire.
Hopefully it's in there. :)

Well i found bits of yellow insulation along the harness but no wire. So it was either pulled out or burnt out. The only yellow wires i see left is one that goes to a connector junction in a clip up above the steering column area and a loop behind the fuse box which i cant tell where it goes, maybe to the eng comp?

So next question would be if i want to use the heater/ac fuse for my stereo what wire is the fused power wire that goes to that??

http://www.gvtc.com/~rlaa/

thanks. I have a copy of that but nowhere on there do i see the anwswers to what im looking for. For one that yellow radio wire isnt even on those charts. Also nowhere do i see any correspondence of wires to specific fuses. Actually looks like the brown connector with 12v in my heater plug goes to the fuse box. I cant figure what the 2nd orange is doing as it never has 12v in my car yet the diagram shows it going to the fuse box connector too

I got it wired up to the brown wire on the heater plug which does go to the fuse. The stereo has 2 power wires, a thick one that requires a fuse and a thin one that says to hook to a acc switched power. I ended up hooking them both up to here. I had originally thought maybe they had the thick one going right to a fuse/battery to preserve the presets/clock but even with them both on this switched fuse, i dont lose my presets. So not sure what the purpose is.

Depending on the type of radio, some will not lose their presets at all, some will lose their presets after the radio internal power supply/volt reg. filter caps have drawn down, some lose presets immediately.

Your presets may disappear after your car has been off 24 hours.

You are right, it lost it a few hours later. So what i will do is rewire the thick 12v wire with a inline fuse to a always on source and wire a ground all the way to the battery on the other side of my cut-off switch. But i wonder if this will now make other items in the car power on when the battery switch is cutoff. Im thinking the radio chassis will now become a new grounding point and everything will try to ground to the battery thru the new wire i run to the battery...

..and a loop behind the fuse box which i cant tell where it goes, maybe to the eng comp?

Probably to power the wiper motor. It can appear to be a "loop" from where is goes from the fuse box to the bulkhead connector.

You are right, it lost it a few hours later. So what i will do is rewire the thick 12v wire with a inline fuse to a always on source and wire a ground all the way to the battery on the other side of my cut-off switch. But i wonder if this will now make other items in the car power on when the battery switch is cutoff. Im thinking the radio chassis will now become a new grounding point and everything will try to ground to the battery thru the new wire i run to the battery...

There are generally 2 grounding points on the dash harness. You can use one of those from the radio chassis.
Brake pedal bracket and possibly the center dash brace is used. (As it is in a 69)

yea i have it grounded now to the dash but thats not my worry. I use a battery cutout switch to shut the car off. If i want the presets to stay alive then i need to run a seperate ground wire to the battery to the other side of my cutoff switch. But if i do that then i worry that everything else in the car will now take that path thru the radio chassis to the battery... So accidently try to start the car with the battery cutoff on, then the radio/ground wire will melt!

I think I saw a cutoff switch somewhere that keeps your presets alive. You might try google.

But, you don't want more than a 1A (500mA would work) fuse for your preset supply. That would eliminate any potential malfunctions if that is your concern. 1 amp won't carry much of anything in these cars.

ahh so your saying to put a fuse on the ground wire? Its the ground wire that im cutting off at the battery and what i would need to bypass.. I think i will just live with no presets, at the moment its the least of my worries with this car!

If you need constant power for your presets, run a wire from the top spade auxillary terminal on the fusebox.

The yellow radio wire connects to the inner most post of the radio fuse. It is also common with the A_C spade next to it in the fuse block... It is the only wire (plus the spade) on that fuse (in my car). This yellow wire breaks out of the wrapped up harness as a single wire (with connector originally) right about where the ignition switch, flasher connector, and cigarette lighter wires do. It pugged into another plug that had the speaker wires in it to make a three terminal plug. The radio is grounded through the radio chassis and support brace. So, it was really grounded to the dash bracing...

The orange heater wire runs from the heater blower in the engine compartment, to the fuse block, to the heater switch and heater resistor. No fuse or power. You're right, the brown wire is the power and goes to the heater switch. It is the only wire on the inner most post of the heater fuse (in my car).

Probably all too late now... I too have seen the disconnects w/ a built in fused wire for providing power to things that need to remain powered. I might end up changing mine to one like it if I change radios (good for alarms, too?)...