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1993 190E 2.3
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Discussion Starter #1 (Edited)
Greetings all,


A quick history of my wifes '93 W201 2.3 since we bought it 12 months ago (fall 2009)...

We bought this car from one of my neighbors. I have known him for 40 years. When he owned the car, he was often outside pampering his car. I think he had it for 3 years before selling to us (he sold it cuz he bought a 300CE). Anyhow, he took real good care of this baby. Because HE was the owner, I had no reservations about buying a 17 yr old car. My wife, on the other hand, was hard to convince. But she gave in (with my persistence). The car is extremely clean!! One week after we took ownership, the head gasket blew! Ya, my wife was real impressed.....NOT! My neighbor felt real bad and helped pay for half the bill (phew!). 3 weeks ago, her car started acting up. First, the rear defog stopped working. Then, the radio stopped working. Then, coming out from the mall, her car wouldn't start. Damn, must be the alternator...? Brought it to a independant garage (that specialize in Mercedes, Porsche). The old German dude connected it to his machine and told me the alternator is not charging on idle. Ok, I went home and removed it from the car. Brought it to a local shop (garage) that rebuild starters & alternators to have it rebuilt ($150cdn tx in). Re-installed in car, gave the battery a charge and all was fine for the next 2 weeks. Then her car wouldn't start again. I then brought it back to the German dude, and again he confirmed that the alt is not charging the battery (on idle). Loosing patience, I returned to the place where they rebuilt it. But this time, I brought the car! The owner/mechanic hooked it up to his machine, and told me that indeed, it is not charging on idle...but it's normal, he says. This is a print out of his battery test results...

Battery Test Results #1
Open Circuit Volts: 12.53 V
#1 Load Volts: 11.22 V
Recovery Volts: 12.22 V
#2 Load Volts: 11.08 V
Rated CCA: 750

Battery Condition: Good, low charge

Charging Results
Regulator Volts: 13.79 V
Peak charging Current: 61.6 A
Diodes: Good


So he tells me that the alternators back then were topped at approx 70 Amps for this car. And that running all the loads (rear defog, heater fan, heated seats, radio) was too much for this type of alt. Huh?? This is the SAME alternator that was in the car before, NOT a replacement! He suggests installing a bigger alt that can give out more than 80 amps. My neighbor never had this problem!!
I must also mention that my wife works 5 mins from the house (short commutes), and rarely takes the highway (she's a nervous driver) to go anywhere. She prefers to take the smaller secondary roads. So the car's RPM rarely goes past 2000.

This diagosis doesn't make sense to me! Does this sound 'normal' to you guys? I absolutely LOVE this car! My wife is freaking out and now wants to get rid of it. :crybaby2:

BTW....the odometer is showing 118k miles (191k kilometers) but with the head gasket job done, this car still has a lot of life in it!

Thanks for the help
Chaps
 

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'87--190E 2.3-16v(being rebuilt), '99--C230 Kompressor
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he's correct in that 90% of the time you are not using EVERY electrical system, so thus the required load is lessened. and i would agree that your wife only using the car for short jaunts w/o ever going WOT is not helping the issue...

even a "rebuilt" alternator is only replacing the brushes that wear down. nothing for the coils or magnets is replaced. so odds are your alternator is shot...upgrade the amperage like your mechanic says...and make sure YOU take the car our on weekends and drive the car like it it was designed to be driven....high speeds for long periods of time (like on the autobaun)
 

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Sounds like a BAD battery that doesn't hold charge, you don't mention how old is the battery

Note: If you have run down the battery to flat even just a few times, your battery is TOAST !
 

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1993 190E 2.3
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Discussion Starter #5
I want to keep my wife happy, so I guess I'll look for a higher amperage alternator so she won't have this issue anymore. The winters up here can be brutal at times so she likes the heated seats! BTW, my neighbor bought that battery a few months before he sold us the car.

My next question now is, can I assume that there IS a higher amperage alt that will fit as a replacement?
 

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'87--190E 2.3-16v(being rebuilt), '99--C230 Kompressor
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talk to the vendor where you got the last work done, he should have what you need...but your still going to have to drive the car on the weekends and give the car a little life back again
 

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1993 190E 2.3
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Discussion Starter #7
Spoke to him and he said he should be able to get one. And yes, I will be opening the throat on the highway. Thanks!
 

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1993 190E 2.3
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Discussion Starter #8
If I were to replace just the pulley on the alternator to a smaller one, thus turning it faster, would this solve the issue? Sounds logical but then again, I'm only a DIY'er. Not a mechanic.

Oh, Merry X-mas everyone !
 

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mercedes 190e 1991 2.3 83 300sd 83 300cdt 97 e320 98 e320
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I had a lot of issues similar as yours first the harness from the alt was loosing 1.2 volts, so I replaced worked better,check ground wiring and it was ok, then I replaced for smaller pulley not much difference, then replaced the voltage reg and no difference, then I replaced the alternator for a similar one and no difference with a/c on blower on 3 and wipers working alternator dropped to 10.5 at idle, so Idecide to go for a bigger alt choose after debating between 90, 115, 150 amps went for the 150amps which I got at Autozone and the part number is 13454 lifetime warranty, same pulley, but you gotta replace the harness cause the sockets are not the same, one is rectangular socket and the other one is O terminal plus the wires are thicker, mine I got in the junk yar just made sue had low ohms in it, now there is a thread on 300s how to do your harness with brand new wires. After that I can keep my a/s on hi, keep my wipers working, put my lights on and it keeps on 13.2 even on idle. Had it running well for a while with no electrical problems at all.
 

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1992 190E 2.3 Auto
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And your mechanic is right, alternators do not produce enough current at IDLE speed to charge the battery
This is not true.Today I started the engine after 3 weeks, hooked the multimeter to the battery to check the voltage.

With the lights on and idling I get 14.4V and that's plenty to charge the battery My alt is the original one (70A).

Then I tested with the A/C (full speed on the fan) on and the voltage went to 13.87 V, which is also enough to charge the batt as well.
 

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This is not true.Today I started the engine after 3 weeks, hooked the multimeter to the battery to check the voltage.

With the lights on and idling I get 14.4V and that's plenty to charge the battery My alt is the original one (70A).

Then I tested with the A/C (full speed on the fan) on and the voltage went to 13.87 V, which is also enough to charge the batt as well.

repeat : alternators do not produce enough current at IDLE speed to charge the battery

- Current and voltage are two different properties of electricity

at idle speed, the little current put out by the alternator is pretty much used up by cars running needs - like ignition, etc. and not enough left to charge the battery

alternator voltage is constant at any speed but current is dependent on alternator RPM.

You can not charge your battery while idling, you need to be running at speed to start charging.
 

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1992 190E 2.3 Auto
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repeat : alternators do not produce enough current at IDLE speed to charge the battery

- Current and voltage are two different properties of electricity

at idle speed, the little current put out by the alternator is pretty much used up by cars running needs - like ignition, etc. and not enough left to charge the battery

alternator voltage is constant at any speed but current is dependent on alternator RPM.

You can not charge your battery while idling, you need to be running at speed to start charging.
Of course current and voltage are different things, I'm an electrical engineer so I know this.

The current and voltage and related in direct proportion (in DC). Anytime the alternator voltage is higher (usually more than 12.7 V) than the battery, current is flowing out of the alternator and is shared between charging the battery and supplying the car needs. When alternator outputs drops bellow battery voltage that makes your battery to be in command and supplying the Amps the car needs.

When you have the case that your alternator is not supplying enough Volts at idle, it wont charge the battery as the alternator voltage has to be higher than the battery to have a charging process.
And this this is the case of our friend here.

Current flows from a higher voltage to a lower.

When alternator applications are designed for cars, engineers take into account most of the electrical loads that a car can have at idle and they make sure that the overall car voltage doesn't drop to a point that the battery is being discharged.
 

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That's what Voltage Regulator does, it tries to keeps the alternator voltage constant between 13.5 - 14.5 volts

When load is high (high current draw) , the voltage will drop to the lower end

A 13.5-14.5 volt reading at idle does NOT mean your battery is charging, it means alternator is putting out just enough current to meet car's electrical demands

A 70A alternator at idle is probably producing only few amps (that won't charge battery), the full 70A is achieved when running over 2500 RPM

electrical engineer ? :rolleyes:
 

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1992 190E 2.3 Auto
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That's what Voltage Regulator does, it tries to keeps the alternator voltage constant between 13.5 - 14.5 volts

When load is high (high current draw) , the voltage will drop to the lower end

A 13.5-14.5 volt reading at idle does NOT mean your battery is charging, it means alternator is putting out just enough current to meet car's electrical demands

A 70A alternator at idle is probably producing only few amps (that won't charge battery), the full 70A is achieved when running over 2500 RPM

electrical engineer ? :rolleyes:
Sure, whatever you say...
 

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92 190E 2.3 SOLD, 91 420SEL, 95 C280
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One more thing to check, and this may sound wierd but the light assembly inside the car (also holds the sunroof switch) may be the culprit.

I went through the whole shebang just like you did and then read somewhere on here about the light and disconnected it to see if that may be the issue. Haven't had a problem since.

Good Luck
 

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2000 :W220 - 1986 W201: 16v Nam,16v Euro- 2002:SL500 Silver Arrow.2002:Avalanche-
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Here we go again ,same shit I'm dealing with today, had alternator out after experienced with battery drain down ( after full bench charge) twice.Alternator physical body looks good and clean , replace brand new Bosch voltage reg/brushes back together to the car with bat freshly charge at 13V, car ran at idle 800-950 rpm with all lights on for 15 minutes bat drop slowly down to 9-8.5v all lights were dim out and bat continue drop and : DEAD . Measured voltage from alternator while engine running the result was same as battery and continue drop mean NO CHARGING at all wtf..hehehe. what was went wrong guys...tell me please.

New and old Voltage regulator..sorry for bad picture.


Alternator
 

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1989 190E 2.6 auto
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I'd look for a bad ground or bad electrical connection somewhere.

In my case, I found corrosion under the little rubber boot at a connection on the alternator...barely noticeable. It was like a thin, hard white layer. I wire brushed it, applied some dielectric grease and a new boot and end of problem.
 

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Obviously alternator is not charging.

Start the car, open ground cable from battery, if car dies then alternator is toast or bad connection from alt to battery or to ground
 

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1988 W201 190E
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Obviously alternator is not charging.

Start the car, open ground cable from battery, if car dies then alternator is toast or bad connection from alt to battery or to ground
Be careful running this test, if you have any sensitive electrical equipment in the vehicle running at the time when you disconnect the battery terminal it can have pretty nasty consequences. The battery is essentially what filters any spikes coming from the charging system. I'm seen ECU's GPS units and ICE units killed when the battery has open circuited while the car was running. It's not so much the disconnection of the battery but the resultant spike when it's reconnected or the collapsing magnetic field from the alternator when the engine is stopped while it's open circuited than does the damage.
 

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Be careful running this test, if you have any sensitive electrical equipment in the vehicle running at the time when you disconnect the battery terminal it can have pretty nasty consequences. The battery is essentially what filters any spikes coming from the charging system. I'm seen ECU's GPS units and ICE units killed when the battery has open circuited while the car was running. It's not so much the disconnection of the battery but the resultant spike when it's reconnected or the collapsing magnetic field from the alternator when the engine is stopped while it's open circuited than does the damage.
OK. What you say makes sense, though I have never seen it myself.
Better safe than sorry, I suppose.
 
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