Alternator not charging battery when headlights on

[levidholman]

When I turn on my headlights or when they turn on automatically, the alternator stops charging at 14.4 and drops to 12.5 for days periodically, this only happens when the headlights are turned on other than that the charging system charges at 14.4. The dealership has replaced the alternator, ecu, and cleaned up grounding points but the problem is still there and now they are refusing to do anymore repairs what should or can I do about this?

 

[Mark_888]

When I turn on my headlights or when they turn on automatically, the alternator stops charging at 14.4 and drops to 12.5 for days periodically, this only happens when the headlights are turned on other than that the charging system charges at 14.4. The dealership has replaced the alternator, ecu, and cleaned up grounding points but the problem is still there and now they are refusing to do anymore repairs what should or can I do about this?

Questions:

1. What is model year and trim level?
2. Where/how are you getting the voltage reading from?
3. Is there a warning light of some sort regarding the battery/charging system telling you something is wrong?
4. Have you had any observed electrical or starting problems?

 

[levidholman]

2013 hyundai genesis sedan 3.8
voltage reading from plugin volt meter and multimeter
no mil light or dtc codes
no other issues

And I'm starting to think that the AMS Alternator Management System is malfunctioning.

 

[landtuna]

Not sure what you mean by "plug in" but alt voltage should always be measured at the generation point. If you are measuring it later in the electrical loop it will appear lower due to the headlight drain. Also, make sure the battery is fully charged then check what the charging rate should be. It will be lower if the battery has a full charge and you don't have power hungry accessories running.

What did the dealer's shop say about the charging rate? 13.7V seems reasonable to me.

 

[levidholman]

Not sure what you mean by "plug in" but alt voltage should always be measured at the generation point. If you are measuring it later in the electrical loop it will appear lower due to the headlight drain. Also, make sure the battery is fully charged then check what the charging rate should be. It will be lower if the battery has a full charge and you don't have power hungry accessories running.

What did the dealer's shop say about the charging rate? 13.7V seems reasonable to me.

because whenever I use my headlights my voltage drops to 12.5-6 they now say that the $1600 positive battery cable needs to be replaced which isn't covered under warranty, I dont have confidence in them anymore after replacing the Alt and Ecu and that didn't fix the problem.

 

[jlindh]

Read the voltage at both ends of the cable.

 

[guybo]

Use the voltmeter directly on the battery connections. they say that the pos batt cable needs to be replaced, check there and see what the voltage is with the lights on and lights off. Then check right at the alternator. Also, have you had your battery load tested? Make sure there's no corrosion at all and check that the terminals are tight- NO PLAY at all.

Often times a mechanic will overlook the most basic thing by mistake and batt term connection issues are often the first thing they miss.

 

[landtuna]

because whenever I use my headlights my voltage drops to 12.5-6 they now say that the $1600 positive battery cable needs to be replaced which isn't covered under warranty, I dont have confidence in them anymore after replacing the Alt and Ecu and that didn't fix the problem.

You can get a custom made cable for a lot less than $1600. Just find an automotive shop specializing in electrical. But before you do that take the advice above and check out the voltages and connections yourself. If that is not doable or you want more expert advice take the car to that shop specializing in electrical issues and ask them to do a check out. I am not believing the dealer's story.

 

[84FordMan]

It's a generator not an alternator, the difference between the two in today's terms is:

- An alternator produces a charge as long as it is spinning and the voltage regulator just caps the voltage output.

- A generator is controlled by the PCM, it only charges when the PCM commands it to.

Long story short, bigger cables will do nothing but make your wallet lighter.

 

[landtuna]

It's a generator not an alternator, the difference between the two in today's terms is:

- An alternator produces a charge as long as it is spinning and the voltage regulator just caps the voltage output.

- A generator is controlled by the PCM, it only charges when the PCM commands it to.

More differences:

An alternator produces AC current and can produce it at very slow RPM's.

A generator produces DC current and needs something above idle speed to produce.

______________________________

Help support this site so it can continue supporting you!

 

[kn5owa]

More differences:

An alternator produces AC current and can produce it at very slow RPM's.

A generator produces DC current and needs something above idle speed to produce.

The last car I had with a generator was a '53 Olds. The development of solid state high current rectifier diodes made the use of alternators feasible.

 

[landtuna]

The last car I had with a generator was a '53 Olds. The development of solid state high current rectifier diodes made the use of alternators feasible.

Wow Kemo Sabe.....you older than me!

Generators were used up through some models until the early 60's. Alternators were a big selling point for Chrysler products then.

I remember learning how to rebuilt generators in auto shop in '62. Alternators, not so much. My '50 Willys had one. Damn thing was as heavy as an A/C compressor.

 

[kn5owa]

Wow Kemo Sabe.....you older than me!

Generators were used up through some models until the early 60's. Alternators were a big selling point for Chrysler products then.

I remember learning how to rebuilt generators in auto shop in '62. Alternators, not so much. My '50 Willys had one. Damn thing was as heavy as an A/C compressor.

Depends on how old "me" is - I'm not telling - they might take my big whomping 5.0 away from me.

Chrysler was, in fact, a pioneer in automotive electronics. They were among the first to put "transistor ignition" systems in cars.

And, the result was that they also pioneered in having the most cars towed since the early solid state ignitions couldn't take the heat and failed like crazy - catastrophically.

 

[Bill K]

I had an old 61 Chevy in college. It got around 25 miles per quart of oil.
The generator was small. Only 5"-6" in diameter. When I got my first car with an alternator, I thought......"What's that thing".

 

[kn5owa]

I had an old 61 Chevy in college. It got around 25 miles per quart of oil.
The generator was small. Only 5"-6" in diameter. When I got my first car with an alternator, I thought......"What's that thing".

Back in those days, generators, mechanical voltage regulators, and distributors w/ "points" kept mechanics in business. One might also add carburetors.

 

[landtuna]

Back in those days, generators, mechanical voltage regulators, and distributors w/ "points" kept mechanics in business. One might also add carburetors.

Generators were usually good for the life of the engine but rebuilding them was easy - if a bit time consuming. Voltage regs didn't usually need any attention unless they burnt shut then it was simple just to replace them.

"Points" were another story. If you didn't have a late model GM distributor it was a PITA to set the dwell. GM owners were luckier in that a hex wrench could adjust the dwell while the car was running.