Can someone please help me?!?! Alternator maybe?
 

1990 190E 2.6

Here are the events leading up to my current situation:

My car would die from driving continuously with a/c on, high speed aux fan on, radio on. I tested the battery and noticed that it would be at around 12.3....battery was only 1 yr old, but temp out where I am is 100+*F, nevertheless battery was relatively new. I had a warranty so I swapped the battery out for a brand new one, and I checked my voltage regulator which seemed like the 2 spring loaded bushings were quite worn. I replace the VR with a used one that was about 85% new. I replaced my belt tensioner, tensioner rod, and tensioner shock. Today while driving, again a/c on, high speed fan on, and radio on, ambient outside temp was 104*F, I noticed that my car began to pulse, ie, the idle was going up and down (between 5 and 5 and a half rpm steadily, like a wave) I switched on my lights (HID's) and they came on, but they were flashing on and off with the pulsing of the car. I turned everything off except for high speed fans because they were on automatically because my needle was at about 105-110*C. Continued driving and came to a light and car shut off. Got it towed to gas station, tested battery at 10.34v, jump-started car, took battery in to charge up, drove car home. all is well for the time being. Car does not die everyday, but on days when I am driving for hours in the city, not highway. and stopping and going, it seems as if the constant engine running in the heat with the load is causing either the alternator or battery to die. Does this sound right? Any suggestions on what the probalem can be? I had the battery and alternator tested and battery is of course good and all components of alternator (diode, voltage regulator, and one other thing they said) are good. I'm going to see if my belt is tight enough, but I did not hear any squeaking when driving. Sorry so long of a post, but I need help ASAP because I will be driving tomorrow under the same conditions. Thanks.

I assume you have the Bosch 80A alternator. My 300TE had this alternator and I never had a problem with it keeping up with the discharge rate but many people on this site have upgraded their alternators to a 143A alternator to cure the situation you have where the discharge rate exceeds the output of the alternator. This is especially true in hot weather where the auxiliary fan runs on high speed, headlights on and aftermarket stereo pumping. Here is a link to one conversion.
http://www.peachparts.com/shopforum/car-audio-multimedia/53236-installed-143a-alternator-my-w124-86-95e-class-photos.html
If you haven't had a problem with this in the past simply replace your alternator with a quality rebuilt stock alternator and enjoy your MB. Good luck, Mark

test the battery with the car running an no load on it... alternator reading?


then slowly put some accessories on ... alternator reading?

that should tell you if its the alternator

i say all this as my car is dead in the water with a starting issue LOL

I tightened the belt, it was loose to the point that I could slip it over a pulley with mild to moderate force without loosening the tensioner. Lee, I took your advice and here are the readings at idle:
1. no load ~ 13.78v
2. lights ~ 13.4v
3.lights, a/c ~ 12.7v
4. lights, a/c, high speed aux fans, radio ~ 12.4v

all readings are an approximate estimation of where the multimeter was fluctuating. I'll see if tightening thee belt helped tomorrow

It is possible that the slip rings (where the brushes make contact) are worn.

Replacing the rings is possible but requires some skill and tools.

If the alternator was not replaced/rebuild in recent years I would replace it with a rebuild one. Don't buy a used one, probably just as old and worn.

It is easy to check the rings, just remove the regulator with the brushes and feel the rings with you finger
On this page you can see the difference between the worn and new rings. Not the same alternator but the principle is the same.

Second I would not trust a used regulator, the brushes may be ok but one of the rectifiers may be blown.

ROb

You have the high speed fans jumpered for the a/c? Thats about 20-30 amps of draw right there. (Thats what mine draw at least). Figure HID's draw 4-5 amps each (from what I saw a 35W HID's ballast will draw that)...

My recommendation is that you install a higher output alternator. That is the best solution.


This is what I have on my 300D. It will also fit the 190. I don't recall if I had to clock the alternator or not...

99 02 Mercedes ML430 ML500 ML55 Alternator Generator New 0101548302 Bosch | eBay

We were having the same problem on my 420SEL, power output would drop when load increased to the point where it would slowly kill the battery.

If you're going to replace the alt, just get a larger amperage unit. No sense in wasting time on the lowly 80A unit. I second the comments on the used regulator. They're only $20-$30 new.

A bad rectifier might manifest itself as AC coming out of the alternator. A DMM across the battey in A/C voltage mode should reveal that. AC across the battery should be very very low.

Well tightening the belt definitely helped the situation. Battery is now being properly charged. However, I do agree with the alternator upgrade. Thats something, I've been looking at for a few weeks now. I believe a 1995 S 500 alternator (143/150 amps) would be a direct bolt on fit on the 1990 190E 2.6, correct? Does the 1999-2002 ML alternator also fit a 190E without any modifications? Thats something I intend on doing in the near future, in addition to my manual engine water cooler.

Do it! Upgrade. You will not regret it. The 143/150 amp alternator from the S500 does fit that 190E. That's whats on mine. I went to the Advance Auto and told them I needed one for a 95' S500 and they got me one.

Sadly I had to return the first TWO they gave me because they just stopped working randomly. I was mad, but third times the charm. Its been working since 08 without any problems.

One thing you must do is SWAP THE PULLEY from your old alt. I didn't do this initially and had a supremely annoying belt chirp for years. A few months ago I bought the proper pulley, installed it and a new belt and BAM quiet!

The ML alternator is the 150A variant. Thats whats on my 300D. It should fit just the same.

You'll need to upgrade the power wiring going to the battery.

Yes, I almost forgot about the wiring upgrade as well. I think someone mentioned either a 0 ga. or 2 ga. wire. How do I get the pulley off the old alternator? Or do they go bad and should I replace it? Also, does it matter what brand alternator? I can get one locally from a parts store that is not Bosch brand, otherwise I need to order it. I have seen acdelco, ultima, bevk/arnley, and another brand.

In my 300D (150A) I used 0 AWG from these guys:
Knukonceptz product detail for KCA KABLE 1/0 ULTRA FLEKS RED CCA POWER / GROUND CABLE

Amazingly flexible!

You will either need an pneumatic/electric impact to take it off..or a breaker bar and some way to brace/lock the rotor. I have an pneumatic impact. But I've done the breaker bar method when a friend borrowed my impact and I was impatient. It worked just as well.

I believe my 190E's is from Advanced Auto and is a "Worldwide Alternator" but it looks like Advanced dumped them (or they changed their name) and are going with:
Buy ToughOne Alternator - Remanufactured - 150 Amps 13393 at Advance Auto Parts

Will a 1995 S 600 alternator fit on a 1990 190E as well?

Yep.

The AL0162X is the 143 amp unit.
Not sure of the 150 amp unit's number.

Just be aware that you might have to clock the alternator 180 degrees so that the connections clear the engine (physically). I had to do this on my 300D. I dont recall doing it on my 190E though.

what do you mean clock the alternator?

rotate part using mounting holes