Skip the auto shop - Our mechanics make house calls

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

asked by on

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 what we are missing? Please we are desperate. Some people say the computer...some say the big black cable leading out of the alternator which we can not find the name for. We have been without the car for months trying to get this solved . Would appreciate any help at all. Thank you for your time.

My car has 75230 miles.
My car has an automatic transmission.

A: If you check the big black cable from the a...

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 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!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Engine sometimes cranks, sometimes doesn't. Battery is fine.

Hello. There are a variety of reasons for why the car may not start. This may very well be a loose wire or bad grounding to the battery or potentially even a bad starter relay (this is usually noticed by...

Q: crank but not start

Hello, thank you for writing in. When it comes to vehicles that crank but do not start, there are several tests that can be done. There are a few that need to be done first before you should progress to...

Q: Car doesn't recognize the key when it's inserted

There are several common possible issues. Low battery voltage can cause this type of situation to occur. Another possibility is a problem in the drive authorization system. The key itself is also something to consider. The drive authorization system needs...

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 P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
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...