A hideaway radio is the best way to get modern audio into a classic car while keeping the original dash completely stock. The radio itself is mounted out of sight, usually under the dash, under a seat, or in the glove box area, and you control it with a remote, a small control head, or your phone. Your original radio can stay in the dash for looks, or you can fill the hole with a blank plate. This guide walks through a typical hideaway radio installation from start to finish: the tools you'll need, where to mount the unit, how to handle the wiring, and when it makes sense to call in help.
If you're still deciding whether hidden or in-dash is right for your car, start with our hideaway vs. in-dash radio guide. This article assumes you've already chosen a hidden system.
Popular Hideaway Radio Options
Browse our hideaway radios category for the full selection. Two of the most popular choices are:
- Custom Autosound Secretaudio SST: A compact hidden AM/FM receiver controlled by a remote. The Secret Audio SST with Bluetooth lets you stream music from your phone, and Custom Autosound's BLUKIT can add hands-free calling.
- Out of Sight Audio Mark series: Hidden amplifier-and-Bluetooth systems such as the Out of Sight Audio Mark III, built for owners who mainly stream from a phone.
Always follow the manual that comes with your unit. The steps below are a general overview that applies to most hidden systems.
Tools and Supplies You'll Need
- Basic hand tools: screwdrivers, a socket set, and nut drivers
- Wire strippers and a quality crimping tool
- Insulated butt connectors, ring terminals, or solder and heat-shrink tubing
- A digital multimeter or 12-volt test light
- An inline fuse holder, if the unit doesn't include one
- Zip ties, adhesive cable clips, and electrical tape
- Primary wire (16 gauge is common for power and ground) and speaker wire
- A drill with small bits for mounting screws
- A flashlight or headlamp. You'll spend time upside down under the dash.
Step 1: Plan Before You Cut a Single Wire
Decide where the radio, the antenna lead, the speakers, and any microphone or control head will go. Measure the mounting area and confirm the unit fits with room for the connectors. Good locations stay dry, have airflow, and are away from heater ducts and exhaust heat. Under the dash or under the front seat are the most common spots. Avoid mounting the unit loose in the glove box. It's exposed there, and we explain why in this post.
Step 2: Disconnect the Battery
Always disconnect the negative battery cable before you start. Classic cars rarely have fuse protection on every circuit, and one slip can damage wiring or the new radio.
Step 3: Confirm 12 Volts and Negative Ground
Modern hideaway radios need a 12-volt, negative-ground electrical system. Many pre-1956 cars and some imports were 6-volt or positive-ground from the factory. If yours still is, you'll need a voltage converter or a proper conversion before installing. Use a multimeter to confirm the voltage, then check which battery post goes to the chassis.
Step 4: Mount the Radio Securely
Use the supplied bracket or a small aluminum plate to mount the unit firmly. A radio that rattles loose will eventually break its connectors. Keep the connector side accessible so you can service it later without taking the car apart.
Step 5: Make Your Power and Ground Connections
Most hidden radios use three main power-side wires:
- Constant 12V (memory): Connect to a source that's always hot, through a fuse. This keeps presets and the clock.
- Switched 12V (ignition/accessory): Connect to a source that's live only with the key on, so the radio can't drain the battery.
- Ground: Run a short ground wire to clean bare metal on the body or dash frame. Sand off paint and rust and use a ring terminal. Poor grounds are the number one cause of hum, noise, and intermittent operation in classic cars.
Use your test light or meter to find a good switched source. The original radio feed often works, but confirm it's actually switched. Old wiring can be unpredictable.
Step 6: Wire the Speakers
Modern radios usually have four speaker channels. Never connect a speaker negative to chassis ground. Each speaker needs both its positive and negative wires run back to the radio. If you're keeping a single factory dash speaker, a dual voice coil speaker lets both stereo channels play through it. Our guide to wiring modern speakers in classics goes deeper. You can browse speakers in Speakers & Amps.
Step 7: Antenna, Microphone, and Controls
Connect the original antenna lead, using an adapter if needed. For hands-free calling, mount the microphone near the headliner or along the upper dash, away from vents and speakers, and route its cable behind the A-pillar trim. Put the remote or control head where you can reach it without looking away from the road.
Step 8: Test Before You Button Up
Reconnect the battery and test everything before you put trim back on: AM and FM reception, Bluetooth pairing and streaming, each speaker using balance and fade, and whether the radio turns off with the key. Turn the engine on too. If you hear whining that rises with RPM, revisit your grounds and look at our post on RF interference.
Step 9: Tidy Up the Wiring
Bundle and secure every wire away from the steering column, pedals, heater controls, and seat tracks. Loose wires under a dash can get pinched or snag on your feet. Label the connections. Your future self will thank you.
When to Call for Help
A hideaway radio is a very doable weekend job for most owners, but it's worth getting help if:
- Your car is 6-volt or positive ground and you're not sure how to convert it
- The under-dash wiring is brittle, spliced, or shows signs of overheating
- You're adding amplifiers, subwoofers, or extra speakers and need help planning the system
- Fuses keep blowing or the radio works only some of the time
Our team helps classic car owners with installs every day. Call us at 574-226-6676 with your year, make, and model, and we'll help you choose the right system and walk through the wiring.
Frequently Asked Questions
Do I have to remove my original radio to install a hideaway radio?
No. Many owners leave the original radio in the dash for looks and mount the hidden unit elsewhere. Some systems can even use the original radio's speaker location.
How long does a hideaway radio install take?
Most owners finish in an afternoon to a full day, depending on access under the dash and how many speakers are being wired.
Where is the best place to mount a hidden radio?
Under the dash or under a front seat, in a dry spot away from heat and moisture, with room to reach the connectors.
Can I install a hideaway radio in a 6-volt car?
Not directly. Hidden radios need 12-volt negative ground, so a 6-volt car needs a voltage converter or electrical conversion first.
Why does my radio make a whining noise?
Engine-speed whine is almost always a ground problem. Make sure the radio's ground goes to clean bare metal, and check the engine-to-body ground straps.