Humidity..
 

Hello

I have a 1983 MB W126 300SD 421k km.
5 weeks ago i took the beast to the car wash, i wass the only guy in the car wash so the boys did a very good job, so it took around 20 minutes, it was very humid inside
I tryed to start the car no luck, got boosted car started fine, got home the car didn't start however if i boosted it was starting ( i drove it for one hour, shut down the car try to restarted no luck).
So i decide that it was my batery, changed for a new one, everything was fine.

yesterday it was snowing/raining and humid got to my friend house and the car wasn't starting, i boosted the car and she started, drove it for about 30 minute got home shut down the car, try to restart the car wouldn't start..

Where should i start looking ?
My alternator ? ( i do have the little batery light on my dash sometimes is on sometimes is off when i'm accelerating the light is off)

But if my alternator wasn't working my battery wouldn't last for 5 weeks of starting/driving...
My batery is new so i will take it out of the equation.


Any suggestion ideas are welcomed

Perhaps your alternator isn't putting out full output. Only bringing battery to 50% or so.
I am assuming when you changed your battery you cleaned the contacts real good.
Check your grounds where ever they attach to the chassis and engine.

Sorin,

Sounds like your alternator brushes are worn. These can be replaced individually if you are very frugal and find just the brushes from a source, or you can buy a new voltage regulator, which comes with the brushes. In any case you have to remove the old voltage regulator, which is on the back side of the alternator. There is a spring clip that holds the electrical connection down (a plug connector) and then two screws that fasten down the ears of the voltage regulator flange. There should also be a noise suppressor connection to ground on the case of the alternator that may be in your way. The old alternator kind of rolls out and the new one rolls in. The new one will be a little harder to get in than the old one was to get out, mainly because the brushes are several cm long on a new one, and they must be pushed into their housings against a spring load as you roll the voltage regulator to insert it. The red light should never come on with the engine running, and it is feasible that at higher engine speeds you actually make enough voltage with worn brushes to make the light go out. Also, Diesels don't use that much electricity when running except if the headlights are on, so the battery charge can last quite a while. Good luck and I hope this helps. Jim

I cleaned the 2 connectors on the battery.
2 questions
how do i test my alternator charging capacity ?
where is the grond attached to the chassis ? that might be the weakest link

You could load test your battery with a load tester. If it test good then I would look for a ground issue. I don't know where the ground straps are are on the MB, I've had other cars with similar issues. If your battery tests bad then it would point towards the alternator. Also look at the conections on your starter to see if there is any corrosion.

Thanks for the quick reply and good explanation

the red battery light is there since i bought the car this June i will buy the voltage regulator and get rid of the little batery light.

Sorin,

Easy alternator test is a voltage check. You should read about 14.5 volts when the engine is running high idle or faster.

P E H

I would suggest that the alternator voltage should be between 13.6V and 14.0V on a fully charged battery depending on load and engine speed.
As the alternator charges (from a cold start) the voltage may reach up to 15.0V, but should never exceed that voltage for more than a second or two at the most. The voltage should then drop back to the 13.6 - 14.0V range.

An alternator which consistently has an output of 14.5V after recharging the battery will "cook" the battery.

Please remember that the battery is important to the alternator, to moderate the output and allow the regulator to operate correctly. DO NOT OPERATE THE ENGINE UNLESS THE BATTERY IS CONNECTED. The alternator and most other electronic devices in the vehicle WILL BE DAMAGED.

Just to make sure how do i mesure the output of my alternator ?
at the batery?
or at the alternator ?

Sorin, You check at the battery, but if possible any local automotive repair shop can check it for you, that's if your able to get to the repair shop. Sounds like your Altenator is giving you some fits. I'd make sure I was getting proper ground before I made a change on the altenator. Perhaps in the change of a new battery it wasn't properly grounded. This will keep your altenator from charging the battery. Some Automotive repair shops will try and sell you a altenator when it was only a ground problem.

The correct place to measure the voltage, is at the battery terminals.
Use a multimeter (digital may give greater accuracy ??)

I have the results

Battery with engine at off after 2 day of non-starting 11.66 V

I boosted my car with my jetta and to start it i need to keep the pedal floored at 3000 RPM if not it will not start


car running at 900 rpm (normal idle) 13.10 V
at around 1500 rpm 13.50 v
accelarating the voltmeter went up to 14.05 volts.


at higher then 1500 rpm my batery light goes off......


can my battery go dead ?? is still under waranty
the alternatorr seems to charge okay...(it's been cold the last couple of day -10, -15 maybe my battery needs the full charge)

I let the car on "idle" 1200 for around 45 minutes and i drove it for 10.
My battery is reading 12.18 and it's starting after i shut off the engine.. but is a bit warmer then the last couple of days.

i will plug the block heater over night from now on ( first i have to test the block heater a quick visual inspection showed no cracks or aother suspect activitys on the wire..)

Sorin,
The alternator is putting out some current, but not much. :(
It may be simply the brushes, or it may be one or more of the diodes in the alternator has gone open circuit.
Check out the brushes, 2 screws and the regulator comes off. Check the commutator while you are at it. It may need to be "touched up" on a lathe to ensure maximum brush life (another 20+ years ;))
If you don't do anything, your battery will be toast. They do not last very long if regularly left discharged below 50% "state of charge".
I recently had my alternator die. It was a diode, but it was shorted, so I had no output from the alternator. Unfortunately, the parts to repair would have set me back a weeks wages, so I bought a used one for $Au100 + freight from "Eastern Australia".
In 20'C temperatures, with a fully charged battery, I drove 60 km, with about 20 warm starts (helping #1 son to move house) before it failed to start the engine, all with the alternator disconnected.

When you buy the regulator does it comes with the brushed ?
I looked at the pictures on fastlane and they showed no brushes..
I need to get the car into a garage but i was unlcky it was snowing/raining and my wipers went dead ( i did a nother post i know what to do it will get fixx as soon as i get the car into a heated garage, it SUCKS working in the cold)