Q: Is my charging system working properly?

asked by on

I have a problem with my Audi A6 2005. It stuggles to start when its cold outside (below 0 celcius). I have replaced all 4 glowplugs, checked the glowplug relays and so on. Still problem. It seemed that the alternator didnt charge properly. So I hooked up a voltmeter on the battery when the car was running. Around 12.8V. Same as when the car is not running. I then hooked the meter directly between the alternator case and the output, the big wire from alternator. About 14,5V. So I guess the alternator is ok. I then hokked it up between negativ on battery and output on alternator - 14,5V Good. Then between positive on battery to alternator case - 12,8V. This will suggest a leaking positive wiring? I think the voltage regulator is mounted on the alternator so the wire from the alternator should lead "regulated-current" yes? Should I spend time on following the wire from alternator to battery, or am I missing something here?

Thanks Ekdal

My car has 155000 miles.
My car has a manual transmission.

The B Positive terminal on the Alternator (the big one) should be linked to the battery via a cable that connects at the starter, so you shouldn’t read a voltage difference between the Alternator and the battery positive terminal. You may have a fuse-link in the cable that is broken or the cable itself may be damaged or corroded. The voltage at the battery when the car is running should be around 14 volts. You’re going to have to get under the car to inspect this. If you would like to have a professional sort this out for you, you can contact Your Mechanic to have a technician come to your home or office to check out your charging system and tell you what needs to be done.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 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!
  1. Home
  2. Questions
  3. Is my charging system working properly?

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: Car starts after jump but won't start later on

In order to know if the charging system is working you will need to have the battery charged and tested to see if it can hold a charge and take a load and cranks the motor with out a jump...

Q: '08 Audi A6 - Will not start, stuck in park, tires locked...help!

Hello there. On most modern cars, including your 2008 Audi, there are a series of safety switches that disable the starter or ignition system. Two of these are located under the shifter and the brake pedal. If the switch has...

Q: New relay, has an extra prong. Fan won't stop running after installing.

This is most likely the wrong relay for your vehicle. Either looked up or packaged incorrectly. I suggest matching up the original relay.

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
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...
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.