Skip the auto shop - Our mechanics make house calls

Q: My new battery is draining, and I have tested the alternator and it is good. What can it be?

asked by on

I had the alternator changed 1 yr ago. All the sudden my battery drains, battery is new. Just got it 4 days ago. But it drains. Even while driving. Alternator new had it tested 5 times. Tests come out good. What can it be?

It sounds like you have a parasitic draw. This is when a system in your vehicle remains powered up while the engine is not running. This will cause the battery voltage to drop and eventually cause a no start condition.

The best way to determine which system of the vehicle is causing the parasitic draw is to connect a digital multimeter to the battery with the engine off. You should see the voltage of the battery slowly dropping. Then, remove fuses one at a time and replace them until the voltage level stops dropping. Once the voltage level remains stable, you have found the system at fault.

I would then recommend having a certified professional, such as one from YourMechanic, check for shorts in that particular system and repair as necessary. If you cannot find the source of the draining, then have a professional perform an inspection to determine why the battery is not holding the charge correctly.

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!
  • Home
  • Questions
  • My new battery is draining, and I have tested the alternator and it is good. What can it be?

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: I have oil dripping from the steering damper all the way back to the transmission

I hear you, tracing oil leaks is hard! I suspect as you do that the leak is at the "nose" or front of the engine (possibly at the front crankshaft seal), and the higher oil pressure at road speed and...

Q: Misfire on cylinder 1 causes spark too rich or lean fuel levels

Hello there, the P0301 Cylinder 1 misfire is a common code on your 2002 Chevrolet Trailblazer. When a misfire code is seen it is telling us that the cylinder is not firing as it is supposed too. This means the...

Q: It cuts off when I turn my heat on

Hello, thanks for writing in. If your car is stalling when the heat is turned on then the alternator needs to be checked. If the output is low then this can occur. If that is fine then there may be...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.