charging system problems 93 300E
 

I was driving along and the radio went dead. The ABS SRS ARS lamps came on. I pulled over and shut the car off to see what was wrong. When I tried to start the car, it was dead. I had someone jump me off and I was able to drive 7 miles to my house. The car idled fine but when the head lights, ac, and stereo was on those same lamps came on again. I never got a battery warning lamp. Any information would be helpful.

You need a DC Voltmeter. Measure the voltage across the battery without engine running. It should be right at 12 volts within a couple of tenths. Then start the car even if you have to jump it. The voltage across the battery with engine running should be about 13.8. If it is less than 13 then use your voltmeter for a voltage drop test. Measure from negative battery post to alternator case and it should be less than .1V or so. Then measure from the output connector on the alternator to the positive battery post and it should be less than about a tenth. If it is more on either of these you have a bad connection, find it and fix it.

If the voltage drop is okay but the voltage across the battery with engine running is bad, then kill the engine and remove the voltage regulator on the back of the alternator and inspect the brushes. If worn to a nub or near a nub, click on fastlane above and buy one of their $15 voltage regulators and that will in all likelihood fix it.

BTW, a search would have found dozens of posts like this with the same instructions which would have prevented me from keying them in again.

Good luck,

Thanks
 

Sorry for not doing a search. I am new to this forum. Thanks for the information!! Bryan

No charge back
 

Check your serpentine belt for excessive looseness, or perhaps a major oil leak that might have caused it to slip on the alternator. After you do that, clean your battery posts and terminals nice and shinny with a combo wire brush cleaning tool for batteries, and conduct all of Larry's tests.... BTW, changing the brush holder- Voltage regulator module might bide you some time instead of a RB or new alternator, but those brushes ride a commutator disc thats part of the armature. if the commutator is shot, its time for another unit.....

Dave....

How hard is it, to change the whole unit? Any special tools needed?

If it is similar to the regulator on a 91 300CE, it is just plug and play. Take a look at the part at Fastlane to get an idea, I think it is just two screws.

glenmore
1991 300CE
2000 C280
1990 LS400

I appreciate all the help and quick response!! I hope my problem is just the regulator. I haven't checked the voltage on my battery yet as my multimeter is at my place of work. I did however check the fuse behind my battery, and it was fine. Also would any parts store carry just the regulator, or would it be something I would have to order online?

The voltage regulator may be purchased from this site. Look for the "Buy Parts" icon more towards the top of your display screen.

As Larry Bible stated, it's on the backside of your alternator. 2 phillips screws are removed and out it comes.

Unless you weigh 60 lbs., it will help to elevate the front of the car some. I find ramps useful. Underneath the car you may find a large shroud that will need to be removed. There may be from 4 - 8 small metal screws with a hex head(8mm in some cases). Those come off to remove the shroud. With it out of the way, you'll see the alternator on the passenger side from down below.

New brushes on the voltage regulator are pretty close to 1/2 inch long.

It takes longer to setup for this job than to pull and replace the voltage regulator.

Thanks for the help!! When I woke up this morning my battery was completely dead, it still had enough charge to run the headlights last night. I didn't leave anything on, should it drain that fast?

I have a spare voltage regulator. If you want to try mine send me a PM. Mine is from a 92 300E, I'm pretty sure the 93 models have the same voltage regulator.

On mine, (same year), the VR was RIVETED to the alternator case, not screwed in. It didn't appear to be a swap-out part. I went ahead and replaced the whole alternator... :(

While at it, I replaced the belt.