Charging system woes..... - PeachParts Mercedes-Benz Forum

deerefanatic · #1 12-10-2005, 12:31 PM

I need some help!

I was at a basketball game thursday night and it snowed about six inches in the 3 hrs I was there. When I left, the roads were snowed in pretty deep, so I was bucking through some really fluffy powder. About half-way home (the gymn was about 5-6 miles from my house) the battery light came on. I attributed it to the fact that I was doing 25 in 4th gear, and that with headlights, wipers, etc, that the engine speed just wasn't high enough. I dropped down in to low range (2nd gear) and the rpms went up around 2600, and the light went out. About 5 mins later, the light came on again, and I couldn't get it to go out at all.

yesterday, I was sick most of the day, so I didn't get a chance to look into things (I had plugged the block heater in thursday night when I got home)

this morning, I had to run an errand, so I had my dad start the car while he was outside. He said that it turned right over quick-like and fired on the second time around. But the battery light was still on. He thought maybe my alternator had some ice on it, and after the engine warmed up, it would be fine. I went to leave, and by this time, due to the rear window defroster being on, the battery was so dead that my horn wouldn't work, blinkers wouldn't work, and my headlights were practically invisible. I turned off the car and took my dad's truck instead.

What could have happened? did my voltage regulator freeze? I popped the hood and there is no visible ice or snow on the alternator or the wiring terminal block.

What gives? Hopefully not something $$$

Dervman · #2 12-10-2005, 01:03 PM

First check the obvious things like bad grounding wires/cables. If these are OK then likely the brushes in the alternator are worn out or the diode pack is shot. The regulator cannot freeze. On most models the Brush assembly and diode pack are integrated into one module held in place by two screws on the rear of the alternator. Once accessed it is easy (and relatively cheap) to replace.

deerefanatic · #3 12-10-2005, 02:40 PM

According to the info on my parts website (***************, sorry Fastlane, you're too $$) that brush pack assembly is also the voltage regulator as well. It's the brushes, voltage reg, and diode. ~$23 or so.

I did call the local MB dealership and spoke with the man in service. He said that it is possible that the battery got worn down the night I was driving because of the low engine speed and many accesories (lights, wipers, rear window defroster) that were running. Once the battery got that low, the alternator couldn't excite anymore. Is that so?

Brian Carlton · #4 12-10-2005, 04:08 PM

Quote:

Originally Posted by deerefanatic

I did call the local MB dealership and spoke with the man in service. He said that it is possible that the battery got worn down the night I was driving because of the low engine speed and many accesories (lights, wipers, rear window defroster) that were running. Once the battery got that low, the alternator couldn't excite anymore. Is that so?

The continual stupidity of the personnel in the dealership never ceases to amaze me.

Total and complete BS. The alternator would have kept up with the load unless you were idling down the street for about an hour. Even if it fell behind, that is what "reserve capacity" is for.

Greg300sd · #5 12-10-2005, 04:27 PM

I fought through the same problem almost...I didn't have accessories not work but I kept having a battery light on the dash. I checked cables first, then replaced the voltage regulator (piece of cake), then finally replaced the alternator to get rid of the light. Maybe yours will be something else but I continually had the battery light lit on the dash until I replaced the alternator.

Biggg Willy · #6 12-10-2005, 09:34 PM

I had a very similar problem.

Another symptom of mine was when I had my key is postion 2, only half of my warning lights would come on (the ones in the bottom of my gauge cluster).

The cause? The brushes/regulator unit. It takes two seconds to take out, you don't even need to jack up the car (if you're skinny, and can shimmy). Its on the back of the alternator, you just need a phillips screw driver to take it out (but a phillips socket on a 3/8ths rachet would be better - it'll probably be pretty stuck). Take it out, examin it, clean it, then try it again... If it still doesn't work, replace it. If its still the origninal alt. then it'll need to be replaced soon anyway. Its only a 20 or so dollar part, so no big deal if its not it, at least you've worked it out of the system. Its probably the cheapest common failure on these car$.

If you're lazy like me, doing this is much easier than checking all your connections

.

deerefanatic · #7 12-11-2005, 06:07 PM

I took the voltage reg off tonight. very easy, even from the top of the car. It was very greasy and grimy. The brushes had a lot of life left on them. I used carb cleaner to clean as much gunk off as possible. Put it back on, no change.

I am pretty certain that the alt is working partially though, as the battery light is dimmer when engine is running than when it isn't running but key is on. This leads me to believe that some juice is coming out.

The current voltage reg is a Bosch unit, so I am assuming that it is original. (Due to the PO's track record...)

I will try and check voltages with my DMM with car off, on, on w/ accesories, etc.

Would autozone, napa, advance auto, etc have this part? I don't really want to be without my car for nearly a week waiting for shipping, and can't afford overnight.

JamesDean · #8 12-11-2005, 07:45 PM

this is what they list for that part

http://www.partsamerica.com/ProductDetail.aspx?mfrcode=GPS&mfrpartnumber=265019&parttype=204&ptset=A

i dont think that looks like this thou:

https://www.***************/secure/PartImages/1197311028.jpg

but i doubt they actually have it in stock. they would have to order from another store...

Hatterasguy · #9 12-11-2005, 07:50 PM

MB actually puts a warning in their manual about not running all 4 seat heaters, defroster, climate control, lights, radio, and adjust the seats at idle. If you do so you will draw more juice then the alt puts out. So basicly don't have all your friends play with all the cool stuff in your 560SEL as it idles in the driveway.

Your alt is probably getting weak, I'd have it load tested. Don't ignore it or you will be walking, I'd sudjest carrying a set of jumper cables with you.

boneheaddoctor · #10 12-11-2005, 07:53 PM

Quote:

Originally Posted by deerefanatic

I took the voltage reg off tonight. very easy, even from the top of the car. It was very greasy and grimy. The brushes had a lot of life left on them. I used carb cleaner to clean as much gunk off as possible. Put it back on, no change.

I am pretty certain that the alt is working partially though, as the battery light is dimmer when engine is running than when it isn't running but key is on. This leads me to believe that some juice is coming out.

The current voltage reg is a Bosch unit, so I am assuming that it is original. (Due to the PO's track record...)

I will try and check voltages with my DMM with car off, on, on w/ accesories, etc.

Would autozone, napa, advance auto, etc have this part? I don't really want to be without my car for nearly a week waiting for shipping, and can't afford overnight.

can you hook up a voltmeter and watch it while driving over a period of time...like I said they can become intermittant even with plenty of brush life....

deerefanatic · #11 12-12-2005, 08:45 PM

I hooked up a DMM tonight (straight to battery). Battery voltage sags during cranking, but doesn't come back up past 12.2 volt after start. It will sag if any device is turned on.

Leads me to believe that the alt isn't puttin out a blessed thing.

I am going to see if the shop my dad has the tractor starters fixed at can do a quick check over, maybe they have the part in stock.

Dervman · #12 12-13-2005, 10:23 AM

Sounds like the Diode Pack/Voltage Regulator is dead.
I replaced mine last year with an original Bosch part from a Bosch dealer.
It includes the whole assembly with brushes and everything.
I think I paid about $50.

dannym · #13 12-13-2005, 11:20 AM

Quote:

Would autozone, napa, advance auto, etc have this part? I don't really want to be without my car for nearly a week waiting for shipping, and can't afford overnight.

ShopForum ships faster than anyone. usually in 2 days. You may pay more $$$ but you get quality and you get it fast.

Danny

deerefanatic · #14 12-13-2005, 12:01 PM

You'd get your part in 2 days from *************** too! You live in Florida, and both Fastlane and BuyMBParts have warehouses in Florida.

I am in Michigan! Slightly different posistion on earth!

Russo 85300tD · #15 12-13-2005, 12:56 PM

Replace the voltage regulator !!! Mine did the same thing about 8 weeks ago. It had enough output to keep the alternator off but it couldn't keep the battery charged. Now the Voltage measured at the cigarette light is around 14.0 Volts instead of 12.2 . Cheap and esy to Fix