Q: Q: Alternator not charging battery

asked by on

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!

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.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Q: Alternator not charging battery

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: Dashboard lights on, car runs fine

These lights on together indicate there is a problem in the anti-lock braking/stability control system. This could be anything from a failed sensor to a faulty module. The first thing to do is retrieve the diagnostic trouble codes (DTCs) associated...

Q: How often do you replace a catalytic converter?

This would all depend on the quality of the catalytic converter and whether or not the engine is running rich. If the catalytic converter installed was not of OEM quality, this can be part of the reason that it did...

Q: Q: Fuel pump has no power

This sounds like you may not have any power going to the fuel pump relay. The relay wires should have ground on two wires. There should be power on one wire and switched power on the other wire. To activate...

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...
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...