battery alternator light still on even though i have a new battery and alternator

I have a mercedes 230 kompressor year 2005. i just replaced the alternator and battery-both brand new and both are checked and work fine. But when i start my car the battery/alternator light still comes on. We have checked the voltage of the battery and its good but when we check the voltage in the alternator it seems like the alternator is not charging. We have checked all the fuses and they are good. We checked all the connectors and they are tight. We hooked up the car to the computer to see what codes it shows and nothing comes up. What could this problem be? No one can tell me wh
Experienced mechanics share their insights in answering this question :
If you check the big black cable from the alternator to the battery and there is no voltage with the engine off, then that cable needs to be replaced. On the transmission bell housing, that cable has a 175 amp fuse in the harness that may get shorted on the transmission bracket which would blow the fuse. This keeps the alternator from charging the battery.

The new cable part number is: A203 440 88 32 Positive starter/generator cable.

How to Identify and Fix Common car Problems ?

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It is possible that the problems that you have been experiencing with the bad alternators have damaged the battery causing it to be weak. This would make the Battery Light come on. It is also possible that there is a problem with the fusible link or the alternator fuse for the charging system.
Mercedes-Benz Battery Charge Warning Light

This light indicates that the battery is not charging. This could be due to a problem with your car`s electrical system and it could have several causes, such as a faulty alternator, faulty battery, bad electrical connection or damaged cabling.

One of the most common reasons the battery light comes on and the car battery stops charging is because of corrosion. Whether the corrosion is on the battery cables or cable terminals, it is still a problem that needs to be addressed. Another common culprit for the battery not charging is a problem with the alternator.
A blown fuse could be a cause of the battery light to come on. Excessive voltage in the electrical system can blow the fuse and prevent charging of the battery. A electrical technician can replace the fuse quickly and it an inexpensive fix.
An illuminated battery indicator can be caused by a number of issues, including: A loose or corroded battery cable. A problem with the alternator or voltage regulator. Damaged cells or plates inside the battery.
Some of the most common reasons for a car battery to die repeatedly include loose or corroded battery connections, persistent electrical drains, charging problems, constantly demanding more power than the alternator can provide, and even extreme weather.
Poor ground connections are an often-overlooked cause of low charging output and alternator failure.
Probably, the most common symptom associated with a bad regulator is flickering, dimming, or pulsing lights. To be more specific, you may notice that the vehicle`s: Headlights fluctuate between bright and dim, without you doing anything. High beam isn`t working as expected.
4. A fuse is defective. In some cases, a battery that won`t hold charge might be that way because of a defective or blown fuse. A defective fuse causes a different type of battery drain but, once identified, is relatively easy to fix.
I did a bit of research and found a battery reset is required to resolve the issue. The message can reset by itself, but the car needs to sit undisturbed for at least eight hours. Perhaps with your work/driving schedule the car doesn`t sit long enough.
The question is, can a faulty alternator destroy a new car battery? The answer is that a bad alternator, does not always affect the car battery, especially if the battery is new. However, there are chances that the faulty alternator can kill your new battery.
Contrary to its purpose, an alternator can drain a battery. It`s rare, but it`s possible. A draw on the battery only occurs if there`s a problem with either a component in the alternator itself or connections to it.
Contrary to its purpose, an alternator can drain a battery. It`s rare, but it`s possible. A draw on the battery only occurs if there`s a problem with either a component in the alternator itself or connections to it.
A bad battery won`t usually harm your starter or alternator, however, since both of those components get their voltage directly from the battery, if the battery is underperforming, both the alternator`s and starter`s performance will be affected as well.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

I have Chrysler 300c. Battery light came on, changed battery and alternator but power still getting drained and battery light still comes on.
ANSWER : Hi, thanks for writing in. This may be a sign of a failing starter relay. The starter relay is a small unit near the starter that directs power to the starter from the battery. When this fails, it may cause a clicking sound and will not allow the starter to engage the flywheel when you turn the key. I would suggest having a professional from YourMechanic come to your home to diagnose your starting issue to determine the solution to get you back on the road.

battery alternator light still on even though i have a new battery and alternator
ANSWER : If you check the big black cable from the alternator to the battery and there is no voltage with the engine off, then that cable needs to be replaced. On the transmission bell housing, that cable has a 175 amp fuse in the harness that may get shorted on the transmission bracket which would blow the fuse. This keeps the alternator from charging the battery.

The new cable part number is: A203 440 88 32 Positive starter/generator cable.

my battery kept draining until i bought a new alternator and battery. i have tightened the belt on the alternator but it still die
ANSWER : Hi there. The best way to diagnose why a battery would constantly drain is to review it’s job and how it is recharged. The battery is responsible for powering all electrical systems until the vehicle is started. At this point, the alternator takes over and also continually charges the battery while the vehicle is in use. A battery will drain when one of two things occurs. First, a battery will drain if it is constantly in use; supplying power to an electrical component even if the key is not in the ignition. Second, the battery will eventually die if the battery is not being charged frequently. However, since this is happening every two days, my initial thought would be that some electrical component on your 86 Olds is continuing to draw power from the battery. This is known as a parasitic drain. The best way to determine the source of this battery issue is to have one of our professional mobile mechanics come to your location and complete a battery will not hold a charge inspection.

Car battery light is on replaced alternator battery and starter and battery light is still on.
ANSWER : You may have a failing voltage regulator that could be allowing the alternator to supply too much or too little amperage to the battery resulting in the battery never maintaining a consistent charge as it is designed to. The voltage regulator is a unit that regulates the charging of the battery by the alternator. When the voltage regulator is not working properly, this may result in the alternator allowing too much power to be delivered to the battery resulting in damaging wires and prematurely sometimes destroying the battery. A common sign of this is usually the acid inside the battery boiling causing the battery to swell. You may also smell a bit of smoke due to things potentially getting too hot. In other cases it may result in the alternator not supplying enough power to the battery, resulting in undercharging the battery or not charging it at all. I would recommend having an expert from YourMechanic come to your location to diagnose your vehicle’s charging system.

Battery light came on went and bought a new battery battery light comes on about 1 minute after starting car.
ANSWER : The alternator on this vehicle is computer controlled and if the alternator is not communicating to the computer then it may default to a set charging rate that will show up as good when testing using standard methods. The computer and charging system needs to be tested using a scanner that is compatible that can check and test charging rates. You most likely do have a bad alternator on the car.

We have a new battery, new alternator, new coil pk, new master fuse and the car still won’t hold power.
ANSWER : Hi there. The only thing that I could think possible is causing your problem is that something may not have been correctly installed while your son was completing this maintenance. However, if your engine was difficult to start before this service, it’s possible there are different components that are damaged that simply didn’t resolve the issue. The only way of knowing what is going on with your Trailblazer would be to have one of our mobile mechanics in your area come to your location and complete a car is hard to start inspection.

I got a new battery new alternator put in but my battery just gets drained I keep having to buy new batterys
ANSWER : This may be a sign of a failing voltage regulator or potentially a bad grounding problem causing a draw on the system. The voltage regulator is a unit that regulates the charging of the battery by the alternator. Often times this will result in the alternator allowing too much power to be delivered to the battery resulting in damaging wires and prematurely sometimes destroying the battery. In other cases it may result in the alternator not supplying enough power to the battery, resulting in undercharging the battery or not charging it at all. In either case, I would recommend having an expert from YourMechanic come to your location to diagnose your vehicle’s charging system.

in my car battery warning light appearing while driving.so I have replaced both battery and alternater still light is on
ANSWER : As you may yourself have seen, there are many reports of this fault with the Civic, that is a battery or alternator is replaced only to have the warning light fail to extinguish despite checking every conceivable electrical possibility. Your only recourse is to have a certified mechanic go through that exercise with your car and that involves first attempting to "re-set" the light. If the warning light returns, the alternator output has to be carefully measured both loaded and unloaded. All terminal connections have to be verified including all grounds. Fuses have to be checked for integrity (continuity) and the possibility of shorts, in for example dash wiring, has to be checked. To request this repair, simply request an electrical components diagnostic and the responding certified mechanic will seek a resolution to this.