New car stereo wiring question

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69GT

69GT

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I'm in the process of installing a new car stereo in my Dart. The factory am radio is still in place and hooked up except for the antenna. All of the wiring is done except for the yellow constant 12v wire. Where would be a good spot to make this connection under the dash?
 
Stock factory wiring? If a low draw new head unit. You could do a “Y” splice into the hot wire for the AM radio. If more than that i would run a line to the battery with a fuse inline and a switched relay. If ya have an amp, for sure direct to battery as noted.
 
The AM radio is not "hot." I'm sure he's talking about the memory "keep alive" wire. Get into the fuse panel. There are two busses, one constant hot, the other switched by key "accessory." If it does not have a dedicated fuse I would either pick a point in the box that is fused or add an in-line. There are several "hot" feeds, the courtesy lamp circuit, which might be easy to tap such as the glove box lamp, the brake lamp switch circuit
 
Yes, it’s the power feed for the memory. I will take a look at the fuse box tomorrow. Just thought there might be a hot line under the dash, possibly the lighter plug. It’s been so long since I used a lighter I can’t remember if the key has to be on for the lighter to work or if it’s hot all the time.
 
Lighter may or may not be hot all the time (I think it may vary by year). Dome/map/glove box light have constant hot. Connected to the ammeter is also a good spot, but make sure it is fused if you go that route. Bear in mind that the convertible top switch gets hot straight from the RED side of the ammeter and has a built-on circuit breaker, so if it's good enough for a factory accessory...
 
The fuse box would be the best spot to connect to. My fuse box had empty 1/4”spade piggyback connections, yours probably does as well.
 
hotrod swinger said:
The fuse box would be the best spot to connect to. My fuse box had empty 1/4”spade piggyback connections, yours probably does as well.
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I agree. I installed a vintage 8 track/FM radio in my Duster 340 and connected to the hot battery lead at the fuse box. The player/radio has its own in-line fuse. With 8 tracks, you need constant 12v (not "key on") or the player may be power starved at start up,etc. and damage can occur to unit or tape. Also, if connected to "key on" power, other things are demanding power when you're just listening to the stereo without the engine running. This can result in overheating wires at the bulkhead.
 
I wired my stereo power and stereo memory to the fuse box as seen in the attached pic. Cleanest and best place to connect, in my opinion. Much better than splicing somewhere, gives you a fused connection, easy to trace and diagnose.
27CE3D56-1A2F-4326-BCE8-BA7F4E07C813.jpeg
 
I do have a couple of free tabs on the back of the fuse box to tap into. If I hook up the constant power (yellow wire) to one of them, will I still need an in-line fuse between the fuse box and the radio?
 
If you hook into the fuse box you will not need an additional inline fuse. Each piggyback tab is connected to a fuse. The tab that you connect to will be connected to a fuse that will become your stereo fuses, in addition to whatever is already hooked up.

Just test each tab with your multi-meter to see which ones are hot with the key on and which ones are hot all the time, and that will tell you where to make your connections.
 
Well, I spent the day yesterday installing the stereo and 4 speakers. After connecting all of the wiring from the radio including tapping the red and yellow wires directly to the fuse box, I tried turning the radio on and nothing happened. I double checked everything and it all looks good. I plugged the red power wire to a spare spade terminal on the radio fuse lug in the fuse box and the yellow constant power wire to the brake lights fuse. Also, I have the black wire grounded to the dash. The radio is brand new so I wouldn't think anything is wrong with it but in retrospect I should have bench tested it first.
 
69GT said:
Well, I spent the day yesterday installing the stereo and 4 speakers. After connecting all of the wiring from the radio including tapping the red and yellow wires directly to the fuse box, I tried turning the radio on and nothing happened. I double checked everything and it all looks good. I plugged the red power wire to a spare spade terminal on the radio fuse lug in the fuse box and the yellow constant power wire to the brake lights fuse. Also, I have the black wire grounded to the dash. The radio is brand new so I wouldn't think anything is wrong with it but in retrospect I should have bench tested it first.
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What stereo are you dealing with? Did it come with a wiring schematic? Are you sure it requires two power sources? You do know the radio lug is probably "key on" power?
 
Kenwood. Yes, it has a schematic and the schematic does call for two power sources. Of course I know the key needs to be on.
 
69GT said:
Kenwood. Yes, it has a schematic and the schematic does call for two power sources. Of course I know the key needs to be on.
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Check the voltage on each side of the fuses in the fuse box. A dozen years ago I was working on the factory AM radio in a '70 B-body and it would not make a sound. Come to find out, the fuse read 12v. on one side and 11.7v on the other. I changed the fuse and it read 12v on both sides and the radio came on immediately.

Another thing to check is what the stereo calls for in regards to 2 or 4 speakers and 4 or 8 ohm. However, this would probably affect the sound quality rather than no sound at all.

Just trying to help out, fella.
 
I would always go straight to battery especially if it’s going to be a more than stock system. Auto parts places have nice gold plated battery terminal with extra places for wires, just solder and shrink wrap in a inline fuse
 
Usually yellow is constant red is ignition make sure your ground is as perfect as it can be no rust nothing but bare shining metal
 
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