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1989 300e 3.0L black on black. Stock besides alpine radio/upgraded speakers
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Discussion Starter #1 (Edited)
89' 300e died on road. Electrical powered down. New batt, VR. Still electrical throbs

Hey everybody, 89' 300e black on black here. Absolutely love that car. These are the problems..


First thing I want to say, there is a Cold start problem.
-Takes awhile to start. 2-5 mins. I'm guessing it's something to do with the ovp behind the battery...? Not sure.

Second problem (current main problem) 2 nights ago the electrical started dimming down while driving.. Headlights, turn signals started not to make the indicator clicking noise, instrument cluster lighting started to dim out.

Rpm gauge started to jump sporadically nearing the end. Then car died on road...



Bought a new oem battery ($170) just to bring her home.

Came home, and pulled the negative cable off new battery. And car continued to run on alternator.

Hmmm..

This mourning, after getting passed the cold start, i warmed her up at steady 1,000 rpm (anything under it shakes crazy until reachs temp just below 80 then smooth at idle) let it sit good half hour running.

Everything looked good. Pulled the positive cable off battery and it continued to run on alternator.

So I took her on the road to test it out. Sure enough, turn signal indicator noise died out. Then instrument cluster lighting dimmed and I started rushing home middle of 5pm traffic.

After i made it back home... I had the car still running, i opened the hood and pulled the positive cable off battery and the car died...

?

Tried again hour later in driveway, and same thing.
-Car runs fine initially with/without battery, then 20 mins later it starts dimming out, rpm gauge jumps all over.. Pulled cable off battery to see if it runs on alternator, it dies.)


I have a brand new alternator at hand. But I'm not sure if that's the problem or worth replacing right now.

Any thoughts? I know my way around the car somewhat, able and willing to locate/replace. Any input is greatly appreciated.
 

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Super Moderator
85 Audi Coupe Quattro, 85 Audi Coupe GT, 71 BMW turbo 2002, 73 BMW 2002tii, 85 BMW 635csi
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18,301 Posts
Change out the voltage regulator. Bet the brushes are down to nothing. Check the plastic sleeve too, where the regulator brush sets.
 

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1989 300e 3.0L black on black. Stock besides alpine radio/upgraded speakers
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54 Posts
Discussion Starter #3
In a nut shell

-Cold start
-recently car electrical started dying out while driving. Rpm gauge jumps. Car died on road.
-bought new battery and tested old one it's good.

-pulled cable off new battery while running and car continues to run on alternator.

-half hour later it starts all over again. Electrical starts dimming out. Pulled cable off battery to see if it runs on alternator and it dies automatically.
 

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85 Audi Coupe Quattro, 85 Audi Coupe GT, 71 BMW turbo 2002, 73 BMW 2002tii, 85 BMW 635csi
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:dunno: Bad diode in the alternator?
 

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1989 300e 3.0L black on black. Stock besides alpine radio/upgraded speakers
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54 Posts
Discussion Starter #5
Change out the voltage regulator. Easy task
That's what I'm thinking also. But it runs fine on alternator alone initially, then 20 mins later electrical starts dying out. I pull cable off battery, car dies. Alternator doesn't keep it going later.. Does initially.

Should I just replace the VR? Or just replace the whole alternator that I bought today...?

Once you install the alternator you can't return it... But if it's just the VR, I could return the alternator back at store and save me $100...

Just need to make sure what's the problem here.

VR? Alternator? Ovp relay? Bad wires/contact?
 

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85 Audi Coupe Quattro, 85 Audi Coupe GT, 71 BMW turbo 2002, 73 BMW 2002tii, 85 BMW 635csi
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You do know that disconnecting the battery while it's running will damage the electrical system.
 

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1989 300e 3.0L black on black. Stock besides alpine radio/upgraded speakers
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54 Posts
Discussion Starter #7 (Edited)
You do know that disconnecting the battery while it's running will damage the electrical system.
lol that does look funny, like yeah I'd just pull the cable off the battery while it's running here and there no prob.

But I was put in a pickle and had to find out fast what the problem was. Still trying to figure out whats the problem because it's my only personal car. And it's a great car. I love the late 80's look to it. Especially the 80s electronic outside temp screen. The whole Instrumental cluster, everything. Car is nearly mint looking inside except the zabino (sp?) wood by the gear box that cracked a little. Everything else dash seats doors looks great. Love older Mercedes. Next would be a 400e, then the almighty 500e but that's a little hard to find.. Anyway..

Hopefully nothing burned. Hopefully.
 

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1993 300E, 2003 996 Turbo X50
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Install a new VR and return the alternator if that works. And hope that you didnt damage anything while running the car without a battery...
 

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86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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With a fully charged battery, start the car. Put a voltage meter on the battery terminals. If you get a reading less than 13.4V, it's the voltage regulator. The regulator in on the back of the alternator, held in place by two phillips screws. At NAPA they go for a tic under $40. Takes about 15min. to change out, including any head scratching that goes on.

Good Luck,

Jayare
 

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1989 300e 3.0L black on black. Stock besides alpine radio/upgraded speakers
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Discussion Starter #10
With a fully charged battery, start the car. Put a voltage meter on the battery terminals. If you get a reading less than 13.4V, it's the voltage regulator. The regulator in on the back of the alternator, held in place by two phillips screws. At NAPA they go for a tic under $40. Takes about 15min. to change out, including any head scratching that goes on.

Good Luck,

Jayare
Can a worn down VR shut down the car while driving? Because the electronics started dimming down to the point the car died.

4 times it died on the road. When you stop at a light it gets dim, Give it gas revving it up it starts lighting up again then no matter what it gets on it's last leg shuts down completely...

Charging the battery right now. Will test the terminals in a bit...
 

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86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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Here is what the contacts look like on a worn out and new voltage regulator. These cars are very, very sensitive to correct voltage at all times. If your car drops below 12V while running, especially with the headlights on, all manner of odd behavior will present itself including slowly dying. Trust me....change the voltage regulator.

Good Luck,

Jayare
 

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1989 300e 3.0L black on black. Stock besides alpine radio/upgraded speakers
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54 Posts
Discussion Starter #12
I just tested it with a meter while cars running and I'm getting 13-14.V

I'm going to let it warm up fully and read it again. If I'm still getting 13-14V could it be the alternator acting up?
 

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1989 300e 3.0L black on black. Stock besides alpine radio/upgraded speakers
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Discussion Starter #13
Also I'll just take out the voltage regulator to check if it's worn.

Thanks Jayare!! Pics helped a lot.
 

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W124 Moderator
86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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I just tested it with a meter while cars running and I'm getting 13-14.V

I'm going to let it warm up fully and read it again. If I'm still getting 13-14V could it be the alternator acting up?
A fully charged battery should hold 12.4V. See what your's is after a full charge. Pull the VR (really, it takes no more that 15min. I changed my first one with a small swiss army knife)
and compare what you see to the images I posted. Turn your lights on and see what the voltage is at the battery, again, while the car is running.

Jayare
 

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1989 300e 3.0L black on black. Stock besides alpine radio/upgraded speakers
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54 Posts
Discussion Starter #15 (Edited)
Quick update: the car is running at normal temp, headlights are turned on and meter reads 13V...

It's going to start dimming down here shortly like yesterday/day before...

Also, when I turned on the headlights it sounded like the car "took a little hit in power"

Next step, taking off the VR and comparing it to a healthy one as in that photo. But if it looks run down bad like in that photo I will replace that asap, and see what happens.

EDIT: battery read 12v before I turned it on. New battery. ($170 2 days old. Tested it and it's a healthy one)
 

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1989 300e 3.0L black on black. Stock besides alpine radio/upgraded speakers
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Discussion Starter #16
Man.. The second screw nearest to engine is a pain. Won't unscrew. Rounds out. Even short strong torque twist...

Hit with a flat to loosen nothing. I'll figure it out.
 

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1989 300e 3.0L black on black. Stock besides alpine radio/upgraded speakers
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Discussion Starter #17
Took off the VR.

The 2 "prongs" were worn down low just like that first picture of the bad one.

Installed a new one. First test drive with new VR installed it started showing SAME symptoms.

Parked it, measured the voltage at battery while running and reads 12-13V. On the 13 side more.

Now car is sitting there with headlights on and looks like it's getting better. SRS light turned off. Instrument cluster, headlights are lit fine now.

Maybe it had to "shake" it out at first? After installing the new VR and going for a test drive it showed same symptoms but now looks better..


Gonna go back out and turn fog lights, radio etc to fully put it to the test...

If it doesn't get better now having new VR installed in there... Don't know.
 

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2008 E350 4M, 2016 Audi Allroad, 2019 Audi Q5
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Did you charge the battery all the way up after installing the new VR? If not, ensure the battery is fully charged first before ruling it off.

12.68v signifies a 100% fully charged battery. Since you have a brand new OE MB battery, you want 12.68v.
 

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1989 300e 3.0L black on black. Stock besides alpine radio/upgraded speakers
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Discussion Starter #19
Update

Installed new VR. It's still acting up. Lights throb.

Gas gauge stays on empty. Yellow light stays on. Despite putting $20 gas in. Shows empty.

Interior lights/headlights throb in and out. Later on all the bottom left lights on cluster (battery light etc etc) fade in fade out.

If I put on rear window defroster while have headlights with fog on, car changes tune. Like shifting/balancing electrical power.


NEW VR seemed to help at first, but it's still acting up.
 

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1989 300e 3.0L black on black. Stock besides alpine radio/upgraded speakers
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Discussion Starter #20
Did you charge the battery all the way up after installing the new VR? If not, ensure the battery is fully charged first before ruling it off.

12.68v signifies a 100% fully charged battery. Since you have a brand new OE MB battery, you want 12.68v.
Brand new oem battery that measured 12v today. Charged it too before performing cold start.

Installed brand new VR earlier today. But it's still acting up. Lights throb.

After i installed the new VR, I measured the battery while car was running and got solid 13V. It fluctuates 12-14 but mainly 13 with headlights on. Measured it again, again, and again at 20mins apart to make sure before I got on the road.

So, it looked good to go. Picked up this girl and after awhile on the road I noticed the interior lighting throbbing in and out. Not good, but rpm, headlights, no SRS light etc so seemed ok.

Then I had to put gas in, yellow light. Put $20 in. And started to drive off and noticed the yellow light still ON showing no gas at all. Looked at the gas pump showed $20 just to make sure... but I felt the gas pouring naturally so I know there's $20 gas in it..

Then while driving still with the girl, I noticed on the instrumental cluster all the left bottom lights lit up.. Battery light all of em. Then faded. I started to sh.t myself quietly thinking this thing is gonna die here and leave us stranded in the cold for awhile.

But made it home. Looked at the headlights and they were throbbing. Measured the battery while car is on and got 3-11 volts

Now with the gas gauge dead, on yellow light, even though there's gas in it, I now have no clue how much gas I have in it now. Practically driving blind.

NEW battery. Installed
NEW Voltage Regulator. installed.
Still electrical throbbing in and out. Afraid to even put on the rear window defroster on without thinking it's weighing down the electrical power.
 
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