Skip the auto shop - Our mechanics make house calls

Q: Battery voltage is low.

asked by on

put new alternator in, now battery gauge went from like 16 to 9, also serpetine belt is NOT put on tightly charging system?

My car has 218000 miles.
My car has an automatic transmission.

A: Hello. If the battery voltage reads low on...

Hello. If the battery voltage reads low on the gauge then that is a sign that the charging system is not functioning correctly. If the alternator is brand new then there is little chance that it is the source of the issue. More likely then that, is the loose belt. The alternator functions using the serpentine belt to turn the pulley and generate power. If the belt is loose then the pulley may not be turning properly, which could potentially be causing your low voltage reading. It may be possible that the belt is worn, that the tensioner is bad, or that the belt was routed incorrectly when it was installed. I would take a careful look at the drive belt system, and verify that it is routed correctly. If everything looks okay, I would recommend having a professional technician, such as one from YourMechanic, come to your location to (determine if it is the tensioner that needs to be replaced](https://www.yourmechanic.com/services/drive-belt-tensioner-replacement) or if there is another issue present.

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: My truck won't stay started

Hi there. It sounds as if you are experiencing an obstruction in the fuel delivery system. A loss in compression after your vehicle has warmed up can also cause this issue. I'd strongly suggest having a mechanic, such as one...

Q: Electrical fault

Getting your car broken into is a pain! Often the thieves do thousands of dollars of damage to your car to steal a hundred dollars worth of stuff. It can take a long time to sort everything out. It sound...

Q: My mustang keeps dying.

Hey there. There is a fuse in the fuse junction box within the engine fuse box that needs to be checked. It is a 20amp fuse. There are two fuse link wires that go from junction box to the alternator....

Related articles

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...
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 to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...