Q: Alternator not charging battery

asked by on July 01, 2017

Hi, the problem I am having is that my alternator is not charging my battery. Battery has been load tested and checked with an ac conductance tester and it has passed both times, battery is new. Alternator has been tested twice, the most recent test was performed by a alternator rebuilding specialist on a vat40 tester, Both times it passed, voltage regulator was inspected and is in working condition. There is continuity on the battery cables from the alternator b+ terminal to the battery cable terminals in the trunk, as well as the jump posts in the engine bay. All terminal posts read battery voltage (12.6). The battery light does NOT come on when key is in on position and alternator out of car. The electrical connector that attaches to the voltage regulator shows battery voltage when probed with a multimeter and key is in on position. One of the female pins shows 10.2 volts the other 12.2. No voltage on either pin when key off. All fuses are ok. Thanks for the help!

Battery will not hold a charge Inspection $79.99 - $89.99 Get a Quote

Hi there. To be honest, when the alternator tests as good and the battery terminals are good, this issue is typically very difficult to diagnose. In most cases however, this is either an electrical relay fault to the charging system or the wiring harness from the alternator to the battery has a short. It might be helpful to have a professional mechanic come to your location to complete a battery will not hold a charge inspection.

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

What others are asking

Camshaft position sensor error code P0343

Hello. The P0343 code indicates there is no signal from the passenger side cam position sensor (Bank 1 actually). Given you have changed the sensor, this would suggest a wiring or connector issue. Your mileage would also make me anxious...

My BMW starts, then immediately stalls

The first thing I would look for is air leaks. Your car uses an air flow meter to measure all the air going into the engine. The controller uses this information to decide how much fuel to inject. If there...

2002 Buick LeSabre overheated and now won't start

Hi, Your engine most likely has major head gasket failure and possible oil pump failure also. Running for a long time with the oil light on could have caused major internal failure of the bearings if the light being on...

I.changed my coils and spark plugs on bmw 328! My car is shaking

Hi Wendy. Thanks for contacting us tonight. After these repairs are completed, 80% of the time, this symptom is caused by the spark plug wires being connected to the wrong plugs, a vacuum line that is loose or an electrical...

Grinding coming from tail shaft area of transmission while releasing the gas pedal traveling 25 miles per hour

Hi there. The grinding sound may be coming from a rear output shaft. In most cases, the transmission yoke or output shaft will wear out over time, or when the inner seal has broken. The grinding is typically due to...

Shaking of 2002 Hyundai Elantra

Engine shakes a lot of times because either the engine or transmission mounts are worn, or they are not running correctly. First thing you want to do is--have that motor mounts and the transmission mounts checked. It's old enough, 14...

Check engine light on inhibitor switch

Hi there. Thanks for sending in your question. It's less likely that the inhibit switch is the source of your vibrations or symptoms. It's more likely that something else, such as worn out engine mounts, a vacuum leak or a...

Key button locks the car but doesn’t arm the car

There are a few potential answers to this question. If the original key still arms the vehicle and unlocks the car, then the fault most likely lies with the second key. If both keys do not function, then the most...

Loss of power and misfiring in 2000 BMW 323CI

The first thing you want to check is on the driver's side, the intake manifold and all the plastic there is between the radiator and the engine. You may barely even see them without a flashlight and a little mirror....

Related articles

The Best Used Cars to Buy If You Live in a Tropical Climate
If If you live in a tropical climate, most of your vehicle purchasing concerns will be essentially the same as if you lived anywhere else – you want a car that looks good, offers decent gas mileage, and suits the...
5 Comfortable Sports Cars Your Parents Won't Complain About Riding In
The most comfortable sports cars combine high performance with a smooth ride. Options include the Alpina B6, Audi S8 Plus, and Mercedes-AMG S65.
How to Use a BMW With Comfort Access Technology
The The BMW comfort access technology was introduced in 2002 as a keyless remote system that uses sensors to detect where the owner is in proximity to the vehicle within 1.5 meters (about 5 feet), allowing him or her to...