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: A properly installed system should not drai...

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

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

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: How complicated should changing manual transmission oil be?

Hi there. On many of the older Toyotas, changing manual or automatic transmission fluid wasn't very complicated. The autos had a dipstick and the manuals used a specification of when new gear oil starts flowing out of the fill port...

Q: Should I idle my car if I do not use it that frequently?

Hi. The worst thing you can do is not drive it at all. By you driving the suv once a week should help you maintain the battery and keep the car in good running condition. If you drove it a...

Q: My car is leaking light brownish half dollar size kind of right under the glove compartment is for almost 2 weeks

Hello. There are a few common causes for a light brown leak. You did not mention whether the leak was under the car or inside, so I will provide an answer to both. If the leak is outside...

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
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...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.