New alternator and car still dies
11-23-2002, 12:22 PM
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1990 300E
New alternator and car still dies
Any suggestions? I just purchased a 1990 300E and put a new battery and new alternator in it but it still keeps dying. I was driving last night and the lights went out and I lost all power. Also, when engaging the locks, some motor is continuing to run and runs down the battery. I can hear it when I get in the car and the battery has run down. I think these are two separate problems but I don't know how to proceed.
11-23-2002, 08:14 PM
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260E , 1989 (for now)
My guess is something is draining the battery down when stopped.
But, with a new alternator and battery, it would be surprising the same problem cause the car to die when running.
1) try to located the source of the battery drain. With the engine stopped, you should be able to isolate which circuit is active, using a multimeeter. Check it at the the fuse box.
2) Check all major grounds (battery cables)
JackD
But, with a new alternator and battery, it would be surprising the same problem cause the car to die when running.
1) try to located the source of the battery drain. With the engine stopped, you should be able to isolate which circuit is active, using a multimeeter. Check it at the the fuse box.
2) Check all major grounds (battery cables)
JackD
11-23-2002, 09:30 PM
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E420 Sport
I've got your solution!
My 1990 300E did exactly the same thing when I bought it three years ago. It was dissapointing to let the car rest overnight and find the next morning that the battery was dead. And the problem was that I checked the battery voltage with the car and everything off and couldn't see a drain...until after many tests and sleepless nigths, I checked the battery voltage WITH THE CAR LOCKED. Then the drainage was incredibly high.
The next step was to find where the drain was. So I dismantled half of the car to find the CENTRAL CLOSING SYSTEM BOX (I don't have the electical manual nor wire blueprints) UNDER THE REAR SEAT. It is a black rectangular box on the driver's side (left).
I opened the box and found a relay (1"X'1"X1") that stayed working after the car was shut down and locked. This relay closes the windows and sun roof when you lock the car. I took out the relay and the problem was gone.
Now I have central locking of the doors, but the windows and sun roof have to be closed "manually" (pushing the buttons I mean) if they were open when I'm about to leave and lock the car.
I know I have to replace that relay, but in my very hot weather country I almost never drive without the A/C, so the windows are always closed already when I park my car, meaning that I don't need very much the ver nice and convenient "total closing system". In fact I had forgotten this feature until now that your post brought it back to my memory.
Hope that this is your problem because is easy to solve changing that relay, and this, as happened to me, will bring peace for your mind knowing that your car will be ready after the overnight rest.
The next step was to find where the drain was. So I dismantled half of the car to find the CENTRAL CLOSING SYSTEM BOX (I don't have the electical manual nor wire blueprints) UNDER THE REAR SEAT. It is a black rectangular box on the driver's side (left).
I opened the box and found a relay (1"X'1"X1") that stayed working after the car was shut down and locked. This relay closes the windows and sun roof when you lock the car. I took out the relay and the problem was gone.
Now I have central locking of the doors, but the windows and sun roof have to be closed "manually" (pushing the buttons I mean) if they were open when I'm about to leave and lock the car.
I know I have to replace that relay, but in my very hot weather country I almost never drive without the A/C, so the windows are always closed already when I park my car, meaning that I don't need very much the ver nice and convenient "total closing system". In fact I had forgotten this feature until now that your post brought it back to my memory.
Hope that this is your problem because is easy to solve changing that relay, and this, as happened to me, will bring peace for your mind knowing that your car will be ready after the overnight rest.
11-23-2002, 09:43 PM
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1990 300E
Rafael & JackD
Rafael, you are the MAN! It sounds like you lived through this problem. I am sure that you have helped. I had the new alternator checked today and it was bad so I think getting a new alternator and taking out that relay (I prefer manually closing the windows) will fix the problems. The car is GREAT otherwise. Thanks for all your help.
Rafael, you are the MAN! It sounds like you lived through this problem. I am sure that you have helped. I had the new alternator checked today and it was bad so I think getting a new alternator and taking out that relay (I prefer manually closing the windows) will fix the problems. The car is GREAT otherwise. Thanks for all your help.
11-27-2002, 10:03 AM
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2000 S500
Regarding Your Alternator
Does your timing cover have a slight oil leak at the top? If so, you better fix it or your alternator will go bad again soon. The oil leak is a quick, easy, and cheap fix too.
The problem is that the oil that comes out of the top of the timing cover runs down the front of the motor on the alternator side. Some of it may even get on the alternator. And with all the wind blowing around inside the engine compartment, the arcing between the brushes and wire wound part inside the alternator (dont recall what it's called), a build up of cooked oil vapor occurs inside the alternator that prevents it from working. It's called "oil soak" and the alternators on our cars are particularly suseptable to it.
I went through 3 alternators before my rebuild shop told me about this. So I fixed the leak and haven't had a problem since. And it's been 3 years now!
The problem is that the oil that comes out of the top of the timing cover runs down the front of the motor on the alternator side. Some of it may even get on the alternator. And with all the wind blowing around inside the engine compartment, the arcing between the brushes and wire wound part inside the alternator (dont recall what it's called), a build up of cooked oil vapor occurs inside the alternator that prevents it from working. It's called "oil soak" and the alternators on our cars are particularly suseptable to it.
I went through 3 alternators before my rebuild shop told me about this. So I fixed the leak and haven't had a problem since. And it's been 3 years now!
