Skip the auto shop - Our mechanics make house calls

Q: Is my aftermarket stereo draining my battery?

asked by on

Hello,

Installed a new head unit (Boss) with harness but had to run red wires to the fuses to get to a switched circuit. Later battery dies and alternator light comes on so i bring it to a shop and they replace battery and alternator. I let the car sit for 4 days in 30 to 40 degree weather and the car wont turn over but turns over immediately with a jump pack. No lights are on and glove and trunk lights don't seem to be on. Don't have a multimeter but am getting one to confirm. I've heard this is common with aftermarket stereos...
My car has an automatic transmission.

A properly installed system should not drain your battery in 4 days. Obviously, the simplest way to rule it out would be to disconnect the stereo for a few days and see if that remedies your problem. If it does, you will need get your hands on an inductive ammeter that can read milliamps. You can clamp the probe around individual wires to see what the draw is on that particular line. There should not be more than 200 milliamps total draw when the car is shut off. But here’s where it gets more complicated. Your car’s body computer may be active for up to 20 minutes after you turn everything off, so the draw will be higher until the body computer "goes to sleep". That means it can be tricky to measure the shutoff current.Also, if your stereo is hooked into a line that is shared by the body computer, the computer may interpret it as activity, so it might not go to sleep properly. If all this sounds complicated, that’s because it is, but by contacting Your Mechanic you can have a qualified technician come to your home or office and check out your electrical drain and tell you what can be done about it.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Replaced clutch master and slave cylinder, but my car still won't go into gear while running

If the hydraulics are working correctly, there are a couple of things that could be wrong with the clutch that would prevent it from releasing. Unfortunately, any of them will require removal of the transmission for repair. At 191,000 miles,...

Q: Charging system warning light.

Hi There, This may be a sign of a weak battery, a failing voltage regulator or failing alternator. The alternator is responsible for charging the battery while the engine runs by generating amperage and recharging the battery while the engine...

Q: car not starting

If the vehicle worked normally prior to your work on the seat, it would appear that something has happened with the circuits (wiring, terminal connections) in the vicinity of the seat. All of that wiring should simply be verified first...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...