Need help with new stereo setup
 

I have a 77 dodge d100, and the stock radio only has three wires. All new radios have multiple wires. Instructions on the new radios say to just splice into the old radio wires but there aren’t any extra wires to splice into. Has anyone figured out how to get around this?

Hello

What model is your new stereo so we can pull up the manual and see the list of wires?
Other than speaker wires and antenna, I believe the stock radio gets its ground from the rear mounting bolt/bracket and the positive from the “Radio” fuse which in turn gets power from the ignition switch.

I believe there is also a wire for the back light. Dash light wires are usually orange.

Modern electronic radios usually have a “keep alive memory” or battery wire. Since this wire needs 12V power at all times to maintain things like the clock, presets and settings it must be connected to a fused protected non-switched source.

The original power wire for the stock radio would be better suited for the power up/wake up wire as it is a switched 12v source.


Ground will need to be bolted to clean unpainted metal somewhere on the vehicle using a crimp ring terminal.



Use a voltage meter and/or test light to confirm voltage sources (key, battery, lighting, etc.)

If the stock radio was mono I assume your adding new speakers and thus the wires for those speakers.

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This is the back of my radio and the radio I plan on putting in. I found in the dash a set of 4 wires that I’m not sure what they go and one of them is hot when the key is on.

Yup that’s a mono radio.

The black and green wires are for the single speaker in the top center of the dash.
The red is power.
The rear stud/metal casing is ground.

What color is that switched wire you found? Does it also turn hot in the key accessory position. If yes, you may be able to use it for the Jensens Red/Accessory wire.



You will need to added a fused wire from the battery + for the Jensens Yellow/memory wire. (Alternatively using a test light you can find the same thing on the back of the dash fuse box).
Connect the Jensens black/ground wire to something metal.


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Link to Jensen MPR2110 manual below:
https://pdf.crutchfieldonline.com/Im...110MPR2110.PDF

edit
It's also worth noting that the DIN size of the Jensen MPR2110 and stock radio are different. You will need to buy or make an adapter for proper mounting in the stock dash location. I believe you need a 1.5 to 1 DIN adapter.

The four wires I found two of them go to the small lights under the radio, and the other two go down along the floor pan and just end in a connector. I don’t know what the connector goes two though, and the hot wire is a purple one.

I don't know what the purple wire is. I would make sure the radio fuse isn't blown and use the stock radio power wire for the Jensens Red/Accessory wire. Add your battery + wire for the Jensens Yellow memory wire.

The floor wires don't sound relevant but if I had to guess their probably for the cab dome lamp or driver seat-belt buzzer switch as I know both those circuits have connectors near the floor on the driver side. Again not relevant for a radio.

Thanks for the information. I’ll see what I can do to get this thing hooked up.