You fix one thing and two more problems come
 

Well,

After finally getting the brakes done I goto start my 300 and to my surpise..nothing.. it barely cranked. Threw it on the charger...started right up...drive it around 30 some miles maybe more highway and stop-n-go roads...came home..parked in the garage..turned the key off...30seconds later..tried to start it and NOTHING!

I had my amps/subs going but that had never caused a problem before.

I installed a keyless entry a weekago. I have the fuse pulled for the relays for the flashers/horn. The only thing getting power 12v constant is the "brain" and it isnt doing much to drain the battery in 30seconds.

My only other suspect was a underdoor light..which i removed..it was getting power..but the bulb wasnt working..the filament was ok...

I have no idea what could be causing this


I plan on taking it down to Advance have then do that FREE check of the charging/battery

see what their numbers come up with...


anything guys....


thanks again

Kris

The fact that you drove it for 30 minutes and failed to charge the battery to a sufficient level leads me to believe that the alternator has no output, or the battery is in such poor condition that it won't accept a charge.

The former can easily be checked with a voltmeter. Bring the engine up to 2000 rpm and the reading must be 13.5 volts or more.

The latter can be checked by any decent seller of batteries using a load test.

Sorry but your alternator may have just gone weak. It isn't related to your repairs though.

Sounds like a weak battery and a weak alt. Subs draw a lot of amps compared to what the system was designed for.

How old is your battery? 4-5 years is pushing it for a diesel, especially if you live in a colder climate.

when
 

you removed the light did you tape off the socket wires? if not you may be getting a dead short.

tom w

Won't Crank
 

Kris : keep it simple ~ you have a load tester right there ,(the car) all you need is an _analog_ multi-meter like the cheapo $3.95 one from harbor freight ~ charge the battery and see if it'll hold 12.7 volts no load then try to start it and see what the voltage reads ~ 11 volts or better ? your battery is fine , look at starter etc.

Under 12 volts ? battery is suspect .

Once you get it running connect the voltimiter to the cigar lighter and go for a drive ~ these cars have a pretty low charge rate (55 amps) so it'll take some time to get up to 14.0 VDC or higher , manybe not at all if you run the stereo .

to answer some questions:

the battery is just turning 1 year old.
the previous was replaced 6mo. old

the volt reg. was replaced 1 year ago.

i put a volt meter across the terminals..it read 11.8/11.9 VDC..after it sat for a little and wouldnt start.

I will conduct the meter test (2200rpm) etc tomorrow and I'll see what that produces..

As for the cig lighter test...mine do not work. all of them are disabled/unplugged.

i did not tape off those light wires..I would actually like to fix that..i dont quite know whats wrong with it...i touched my meter to it and it says 12v (last time i checked it--2 weeks ago) the bulb's filament was good yet no light...


if the batt is bad...something funny is going on here this (current) battery is the car's 3rd in under 6 years.

if the alt is bad i would like to replace it with a 115amp alt. i think that would help alot. anyone know a good source (not boneyard) relativly low priced?

vwnate1 - u from around me? If not--i didnt know that harbor freight had more locations...hmm ive actually never been there lol but i know the name from around here
Thanks

How is the ground? You should remove the cable and clean the connections. It couldn't hurt.

i just recently cleaned them and cleaned up the ground point for the batt..i did this when i cleaned out my battery tray and sprayed it down with some rust enamel. that was in june im thinking.

I dunno where you're at (I'm in So.Cal.) but Harbor Freight has stores all across America (is this a great country er whut ?) PLUS online ordering .

I'm still using a 35 year old Radio Shack cheapo analog meter when I'm in a hurry , I vastly prefer using good SUN test equipt. or my Bekmann meter but you _MUST_ use an analog meter when trouble shooting starters and doing load tests and the fancy-schmancy digital ones go all wonky under load and stop working altogether if the votage drops below 10 volts...

Try to turn the alternator fan by hand ~ it should be tough to rotate , if it's easy it's time to re-adjust the fan belt.... I hadda do mine on my old '79 300CD to-day as I was doing routne oil change and fuel system mtce., I changed the alt. (55 A unit) and belt in Pecos , Tx. a week and 3,500 miles ago...

A tiny bit of belt slip will cause serious low charging .

ground
 

If the ground for your light is corroded or broke your light won't work, but power will still read 12v if your tester was grouded elsewhere.

did you spray the body were the ground conects if so thats stuff "rust enamel" may not be a good conductor

amps and stuff
 

I had the same prob after installing my amp/sub. took the battery out and load tested fine. I installed a powercap and havent had a prob since. I don't know If I actually solved the prob but from what I understand the mercedes vehicles are particular about power management.

i didnt spray the ground area with anything..i cleaned off the paint with sandpaper and mounted it....ive had my subs since january..this is the first battery drain issue ive had...even when they wernt connected something still drained the crap outta my battery....

test results...

--i tested the underdoor light to make sure it was turning off when the door was closed...volts dropped to 0...that isnt causing the problem.

--i tried to start the car (this morning) it tried to start but couldnt muster the energy to crank it enough...

volts @ battery (after sitting all night) 11.73 VDC

--50amp Starter/Charger connected to battery. I''ve removed the fuse to my amps/subs in the trunk for the remainder of these tests

volts @ battery - 13.94VDC
Battery appears to be completely drained had to wait ~5 minutes before it would start

--engine started
battery volts @ idle (550-600rpm) - 13.74VDC
battey volts when engine revved max - 13.85 VDC

i let the engine run for a little bit (10min) then retested.

battery volts @ idle - 13.74
battery volts @ ~2200 - 13.85 (engine was 60C)

--turned engine off. restarted.

Inserted Key and put to RUN. Volts dropped to 11.50VDC
Started Engine................... Volts dropped to 10.50VDC
Engine running....................Volts slowly climbed to 13.73VDC

--turned off car..observed voltmeter..
Volts - fell quickly to 12.59VDC then slowly to 12.48VDC

--attempted restart 10m later
Volts b4 start - 12.35VDC
Volts when key on - 11.4VDC
Volts when cranking - 10.4VDC
Volts when running - slow climb to 13.74

I checked the alternator belt..it was rought to turn..it had just been adjusted not too long ago

I am going to take my car down to Advance and have them do their tests on it see what they determine...

anyone interpret my results?

how i checked my volts all those times..lol

http://i21.photobucket.com/albums/b2...e/PB260196.jpg

Thanks

Kris