Alternator or Voltage Regulator?
 

I've got an '84 190E 2.3 in the garage with charging issues. At first the only hint for a few days was the battery light coming on. I had just fiddled with the instrument cluster replacing some bulbs, I figured it was just a tempermental gauges since I didn't have any other electrical problems. But after a few days the lights started dimming and the radio switched on and off intermittently. I was pretty sure I knew a bad alternator when I saw one.

Sure enough, the battery tested good, but the alternator read as undercharging. So I plunked down the $190 at O'Reilly's for a new alternator.

But from reading some of these threads, it seems that the voltage regulator is more likely the problem. Is there a way to test the voltage regulator to see if it's the problem or if it is in fact the alternator itself?

Thanks,
Gabe

hi gabe,
from my own experience personal and proffesional. what i have seen it more often than not the regulator is at fault, but before you simply replace the regulator, you need to take sevaral items into consideration about alternators general condition. .
over all you are better off replacing the unit with a rebuilt one, chances are the bearings are worn, and the slip rings where the brushes for the regulator contact are also worn. nothing like having to do the job all over again.

Does the alternator need to be removed to replace the regulator?

No. Two screws secure the voltage regulator to the back of the alternator. It's a simple DIY replacement.

Buy a replacement one and swap it in, they're cheap! As mentioned, two Philips screws hold it in place. Easy to change.

I agree. The regulator/brush assembly is so inexpensive and easy to replace, just do it and be done with it. Chances are it will take care of your problem.

Thanks for your help. I will install the new regulator as soon as it comes in, in 3-5 days >(

I will let you know how it works out.

Gabe

PS BTW, is the regulator the little black rectangle, or the oblong black-on-white plastic thingy?

it's white, but may have a black plastic cover on it.

Disconnect the battery before working on the alternator. You will be taking a screwdriver very close to the main power cable attachment at the alternator.

Sixto

Got a regulator today at Napa Auto Parts, who, incidentally, outperformed my beloved O'Reilly's in nearly every aspect. And the big conveyor belt running through made me feel like I was in some fantasy toy store.

I believe I have fried the battery that was in the vehicle because after replacing the regulator and leaving the house the car died about 4 miles down the road. No surprise, since I'd been charging and killing it several times while running to stores to get my problem solved. Dropped a new battery in there and car is running normally, but I won't know for sure until I have the batt/alternator checked tomorrow.

I did note, however, that the brushes on the old regulator were worn down to practically nothing, maybe 4 or 5 millimeters tall. Either that or the springs had given out. So I am pretty confident that the problem is solved.

Now all I have left to do is to replace the right rear window regulator, charge the AC, replace the left tie-rod end, replace the center vent bezel, fix the odometer, replace the shifter cover plate, and replace the illumination bulbs in the climate control box.

Heh. Looks like I'm in for a hell of a weekend.

Thanks for a your help, folks. I'm pretty confident you'll be hearing from me soon.

Gabe

[iv'e got a w124 300e with 230,000K's on the clock & after replacing 3 batteries, all the auto elecs (3) recon the whole system's fine, done all the earth leakage tests, current draw under load, volts etc etc, well my driving habits have not altered in 8 yrs of owning it so... guess what?? getting the V. Reg. replaced (by an Auto elec who says this is not the problem) We will see.

they are onll AUS$45 from Bosch, so we will c what happens. I'll let you guys know
Graham:rolleyes:

It is the voltage regulator. I just had the same problem, and I ended up trying 3 different alternators and 3 different batteries. I was told to replace the voltage regulator by another MBZ owner, and PRESTO!!! No more problems with the electrical system.

Don't new alternators come with new regulators?

Sixto

Ugh. Not the voltage regulator. Unless I am more of a moron than anyone and don't know how to screw in two bolts, it's not the regulator. Argh.

I will replace the alternator. There goes $40 on a voltage regulator I didn't need.

And yes, voltage regulators come on alternators, so I'm not sure why replacing the alternator (especially 3 times) didn't work. But whatever. With my luck, it won't work for me either. Then I will attach an outboard boat motor to the rear end of the car and have a carboat. Like a houseboat. But on a Mercedes.

We'll see if a new alternator does the trick. Everyone cross your fingers for me.

Gabe

I don't believe I saw your post where you said you changed the alternator three times.

If yours was a new alternator, why were the brushes worn down to almost nothing?

Did you ever actually install the O'Reilly alternator you bought for $190?