Mystery Electrical Problem URGENT - PeachParts Mercedes-Benz Forum

mudditt · #1 02-13-2003, 07:24 PM

Here is a story, if anyone recognises this and knows what may cause it I would love to hear from you.

300e 2.6 1990, 135K

starts first time everytime used everyday.

Saturday am daughter calls me from car on her way to work. tells me that radio sounds funny. gets to work OK. 16 degrees F outside. At 8pm she leaves work, calls me again tells me the radio and the heater acting up. Pulls into driveway, car dies and will not restart.. Lots of clicking no turning.

It sounded like a battery problem. I put it on charge (took 10 amps for about 5 hours before it started to drop.)

The car turns over like a champ but does not fire, instinct says fuel starvation. Check here and ID overvoltage relay as probable cause.

Call shop, have the car towed in. OV relay replaced battery again charged (?). Pick up car drive home ( 6Miles ) Car dies in driveway. (no its not the driveway). Called shop, tech says battery potentially the problem (PEP BOYS 12 months old)

I took the Battery off went to Pep Boys ready to raise hell. They test the battery (50 Minute deep cycle multi stage load testing) battery is good.

I go home put battery on, car starts.

Tell daughter to drive back down to shop as heater fans /compressor not running ( I checked here, sounded like another relay (Klima equivelant).

Shop calls 2 days later car fixed. Daughter picks up car drives less than 2 miles heater going on and off, wipers very slow, calls me in panic. I tell her to turn around go back , she pulls into Dunkin Donuts (no cops around) car dies. I call shop they dispatch tow truck.

Now my experience is out of date, but if this was a mini or a cortina or a capri I would say we had a massive current drain which was sinking the voltage below working levels and I would then start sniffing around earth (ground) connections to the body.

Whatever it is seems to road test fine and then after a while dies.

If anyone has any thing that may help PLEASE reply. I may have to put the tech out of his misery (kidding).

By the way I am now $730 in the hole and smell lawyers and its still freezing here on the east coast.

help

Holson Adi · #2 02-13-2003, 07:28 PM

Could it be the alternator? Well I don't think it is because the electricals in the car can't drain the battery that quickly.. or can they?

When the alternator on my W124 died, the A/C stopped blowing cold air (terrible in the 95F weather in Jakarta and no open mercedes windows unless you're lookin to lose something...), the radio stopped working, windows slow, and horn sounded like a bike's horn...

mudditt · #3 02-13-2003, 07:35 PM

I did think of that but that sort of drain is very high. and it seems not to be constant.. Symtoms seem to be the same tho', yours in hot weather mine in our current white stuff

maheath · #4 02-14-2003, 12:06 PM

That is unusual. I've never pulled into a Dunkin Donuts with no cops around.

Seriously, this does sound like it's alternator-related. It sounds like it's not recharging the battery. I once had a '71 Chevelle Malibu that had a similar problem and it was because the alternator belt was loose.

MikeTangas · #5 02-14-2003, 12:47 PM

When the alternator isn't charging, and battery reserve begins to drop off, the car will begin to shut down non-essential systems in an effort to get you home or some place safe.

Take a look at the brushes (voltage regulator). Mounts to the back side of the alternator with two screws. On many models the brushes can be pulled/checked/replaced without having to remove the alternator.

Break out the DMM and see what your voltage is at the battery with the engine off, should be 12.9-13.2v or thereabout. Then check again with the engine running, should be 13.8-14v.

mudditt · #6 02-14-2003, 01:02 PM

Thanks, I have passed your info on to the shop, it does sound logical. Anyone else with other ideas of a) how to fix it or b) how to stop my daughter from giving me grief !!!!

By the way I think that Donut shop had just opened and the war on terrorism had not reached there yet

mudditt · #7 02-14-2003, 01:07 PM

Back again. Shop found one brush bad on the alternator, they have replaced it and are doing som extensive road tests for a couple of days to see if the problem has gone away.

So this could have been the answer Mike, thank you so much for the pointer

MikeTangas · #8 02-14-2003, 01:13 PM

No problem, glad I could help. We can just meet up some day at my favorite haunt - a donut shop

, and you can pay up. Black coffee and a dozen glazed

.

Meza · #9 02-14-2003, 09:33 PM

You don't to take the car to a shop. This is a classic problem. All you need is a voltage regulator. It's about $40.00 for a Bosch unit and $20 for other aftermarket brands and takes about 5-10 minutes to install. Two small screws and it's out. I ran into this problem several times in MBs and BMWs. The alternator in these cars is SOLID and YOU DON"T NEED TO CHANGE IT unless it makes a bearing noise. As a matter of fact, Voltage Regulators are one of the best insurance items to put in your glove compartment if it was never changed and they usually fail at about 175K miles for Bosch units (from experience).
Good Luck