Why Your Car Stereo Only Works Sometimes

When a car stereo only works sometimes, the problem is usually in the wiring. However, depending on exactly how the stereo is failing to work, you could also have an amp problem, an internal fault in the head unit, or even a problem with your speakers or speaker wires.

These are all faults that can cause an intermittent failure, where the car stereo will sometimes work and sometimes not work, so tracking down the real problem may be difficult unless the fail state lasts long enough to check everything out.

Even if you aren't lucky enough to catch your stereo acting up while you have tools in hand, you may be able to find some clues hidden in the exact fashion that your car stereo stops working.

Troubleshooting a Car Stereo That Works Intermittently

When a car stereo only works sometimes, there are two main types of faults that can be in play. One has to do with the car stereo turning on and working just fine, but the music intermittently cuts out, or the stereo randomly shuts itself off. The other has to do with the car stereo seeming to turn on, but no sound ever comes out.

Here are the most common reasons why your car speakers stop working sometimes, and what to do about it:

1. When a car stereo cuts out and then turns back on:
   The problem is usually in the wiring.
2. If the display shuts off at the same time the music cuts out, then the unit is probably losing power.
3. Tracking down the fault can be difficult when the radio is functioning since it actually has power at that time.
4. When a car stereo seems to turn on but produces no sound:
   The problem is often in the speaker wiring.
5. A break or crimp in the speaker wiring, often where it passes into a door, can cause the sound to cut off entirely.
6. The problem could also be a bad amplifier or bad wiring to the amplifier.
7. If everything else checks out, the head unit itself may have failed.

What Causes a Car Stereo to Turn off and Back On?

If your sound cuts off, or the head unit turns off intermittently, when you’re driving down the road, the problem is usually in the car stereo wiring. This is especially true if the display shuts off so that you can tell that the stereo is losing power.

When a power or ground connection is loose, driving over bumpy roads—or even just driving at all—can cause a connection to break or short. In some cases, the power will return with further jostling, leading to a situation where the radio will only work sometimes, turning back on as suddenly as it turns off.

Locating Loose or Damaged Power and Ground Wires

Tracking down a loose power or ground wire can be tricky, but the best place to start is at the back of the stereo. If you’re dealing with an aftermarket head unit, especially if it wasn’t professionally installed, then you may find connections that are obviously loose or poorly-made.

If you don't find any problems there, you'll have to expand your search. Here are the basic steps to follow if you're trying to track down damaged car stereo power and ground wires:

1. Remove your car stereo.

2. Examine the wires on the back of the stereo.

3. If any wires are loose, frayed, or corroded, you'll need to cut, strip and crimp or solder them back in place.

4. Follow the ground wire from the back of your stereo to where it bolts to your vehicle.

5. If the ground wire is loose, tighten it. If it's corroded, clean the corrosion and then bolt it back in place securely.

6. Follow the power wire from the back of your stereo to the fuse block.

7. If the fuse was replaced with a circuit breaker, install a fuse instead. If the fuse blows, you have a short. Carefully inspect the power wire and replace if necessary.

More In-Depth Information About Damaged Car Stereo Power and Ground Wires

Head unit power, ground and speaker wires can be soldered or use butt connectors, so if you find that they were simply twisted together and taped, that could be the problem. Poor soldering, or loose butt connectors, can also cause a momentary loss of power or ground.

If everything looks good at the back of the head unit, you’ll want to check that the ground connector, where it attaches to your vehicle, is tight and free of rust. You can also check for inline fuses, and check the fuse block. Although fuses are typically either good or blown, there are rare situations where a fuse can blow but maintain electrical contact that breaks sporadically.

There is also a small chance that you may find a former owner of your vehicle replaced the radio fuse with a breaker, which pops and resets due to an intermittent short that they didn’t take the same, or expense, to track down.

If everything else checks out, you could have an internal fault in the head unit. It’s also worth mentioning that some head units have built-in fuses, which you may want to check before throwing in the towel.

What Causes a Car Radio to Only Work Sometimes With No Sound?

If your car radio stops working intermittently, in that you lose sound, but the head unit clearly doesn’t lose power, then you’re dealing with a different issue. In this type of situation, it’s very likely that the head unit is still working, but there is some kind of intermittent break between it and the speakers.

You could also be dealing with an internal head unit fault with this type of problem, but it’s important to rule out the speakers, speaker wiring, and amp first.

One possibility is that the amplifier is going into protect mode. In amplifier protection mode, the head unit will stay on, but it will seem to stop working as you will lose all sound from the speakers.

Amps can go into protect mode for a variety of reasons, including overheating, internal faults, and wiring problems, so it’s important to actually inspect the amp while your stereo seems to be in a fail state to rule that out.

Problems With Speaker Wiring

In some cases, issues with speaker wiring or speakers can also make it seem like a head unit quit working. For instance, a break in the speaker wires leading to a door speaker may cause the sound to cut out altogether and then kick back in when the door is opened and closed again.

Diagnosing something like no sound from speakers is a more complicated issue, but it involves checking the integrity of all the speaker wires and the functionality of each individual speaker to rule each one out in turn.

One of the most common causes of this problem is a crimped wire where the wires pass from the car into one of the doors.

Here are some things you can try out if you suspect this is the case:

1. With the car radio on, open and shut each door firmly. If the radio cuts in, or out, suspect a crimped wire.

2. Open each door and look for the thick rubber boot that goes between the door and the car. Move the boot back and forth, and see if the radio cuts in or out.

3. If possible, peel the boot back and physically examine the wires. This may be difficult, as these boots are usually very stiff.

4. With the car radio on, tap on the interior of the door with your fist. If the radio cuts in or out, suspect a loose or crimped wire.

Replacing a Car Stereo That Only Works Sometimes

There is always a chance that you’re dealing with an internal fault in the head unit, in which case the only way to fix the problem is by replacing your car stereo. However, due to a large number of other factors that can cause a car stereo to only work sometimes, it’s important to rule each one out before you go and install a new head unit.

If you go straight to popping in a new stereo, and there is another, underlying problem causing it to only work sometimes, you’ll end up with the same old problem on top of the bill for replacing the head unit that actually worked fine all along.