1989 300E starting problem

I posted a thread this morning on how to remove the alternator and the starter but before I do so I would like to make sure that these could be the problem.

My 1989 300E had a hard time starting a week ago. When I turn on the key the lights came on, the radio worked, the A/C worked, etc... but the car would not start, not even a cranking sound. I tested the battery and the voltage was 12.57 volts. I then jump started it with my other car and the 300E started no problem. I tested the battery when the car was started and the voltage was at 14.0 volts. I assumed that the alternator was charging the battery. I started it again about 6 or seven times with in 3 days and there was no problem.

Yesturday I tried starting my car and it did not start. Same as before. I turned off the A/C, radio and lights and tried to start it again. It took a few seconds but then the car started without a boost. Now everytime I start the car I make sure that the A/C, radio and lights are off.

I took the car for a drive around town for about 20 min and stopped at a coffee shop for about 10 min but I left the car running. When I returned to the car my ABS warning light came on and my warning light for an exterior light burnt out was also on. The car was also running a little rough. When I turned the radio and A/C off the car ran excellent and the warning lights turned off. When I put the A/C back on the car ran rough and the warning lights came on again so I turned the A/C off again. When I arrived home I turned the car off again making sure that the lights, A/C and the radio were off. Then I tried to start the car right after again and the car did not start, not even a sound yet the lights and radio worked. Today I jump started the car, put the A/C, radio and lights on; the car started no problem and there were no warning lights. I took the car for a 5 min drive and still not warning light.

I assume that the alternator and or starter need replacing. About 6 months ago I changed the voltage regulator on the alternator, Could this be the problem also?

I am sorry that this thread is so long but I wanted to make sure that I got everything in there.

Please help!!!

Fab

[Moneypit SEL]

Truth is, it sounds more like a dying battery than either the starter or alternator. Go someplace and get a charging system check.

[Rob Pruijt]

Most likely the voltage regulator, the cheap ones only last a couple of months, get a Bosch. The alternator is a little undersized for this engine and the regulator wears out rather quickly. I alway have a spare one in my car.

The battery is only a year and a half old, but that is a good idea, I will take the battery to get it checked out. I heard batteries could last 2 months to 7 years. After market batteries are not as good as the original one that came with the car. The original lasted 8 years. This is the third battery in this car.

The voltage regulator is a bosch one, but for the cost of another new one I will purchase it. I thought that keeping an extra voltage regulator in the car is a good idea, I think I will do that.

Thanks

I will let you know what I find out.

[Moneypit SEL]

I've seen batteries that were flatter than the paint on the garage floor when they were brandy-new. What makes me think 'battery' is the fact that it starts and runs when jumped, and your measurement of 14 volts when it's running. The alternator is what raised the system voltage, and nothing on the car draws as much current as the starter. That's why you could have lights and such working, but no start.

Thanks for the help. I will try all of the suggestions today.

Fab

[Rob Pruijt]

Having the battery checked is no garanty that is is good. Checking is done by drawing a lot of current in a small time to see if the voltage drops. If the battery has an internal shortage it may test as good but lose its charge in one or two days. The best way to test it is to charge it to full capacity with a battery charger (check the water/acid level first) and see if it holds its charge.
And of course test with an amp meter for power leaks. It can be something as simple as a trunk licht that stays on.

I got my battery checked out and it is 100% perfect. But just to make sure I borrowed a new battery from work and put it into my car and the car still does not start unless I jump start it. So I know now that it is not the battery. I am going to check the voltage regulator on the alternator to see if it needs replacemen. I called mercedes and they said that the part will cost $95.00 CND. I called a few aftermarket places and they said the cost would be $59.00 CND. How can I tell if the regulator is worn? If after I check the regulator and if it is still in working conditon what else should I be checking. I am still wondering if the starter neededs replacement and or the alternator.

Let me now!

Thanks,

Fab

I took out the voltage regulator. What am I looking for to see if it needs replacement?

Thanks,

Fab

[Rob Pruijt]

Except for the brushes and the wires connecting the brushes to the regulator there is nothing you can test. If you suspect its faulty, just replace it and see what happens.

First of all you should test for electrical leaks.
connect and ampere meter to the battry wire and see is something is drawing electicity. Start with everything off, then swith on all electrical things (including AC) and see what happens. The ABS light comes on if the voltage drops below 12 Volt, that means you are draining your battery. If you buy an ampere meter make sure it can test DC current, most cheap ones only test AC current. For these test (expet the test with everyting off) you will need an clamp-on type of meter.

With a good ampere meter yo can also test the current of the starter. If you can jumpstart it I don't think there is anything wrong with the starter.

I put in a new voltage regulator in. I still had to jump start the car to get it started. I took the car for a drive for about 10 min. I got the car home and turned the car off. An hour later I went back to the car and the same problem. The car will not start. I check for any power leaks and there was none. Could the whole alternator be gone?

Thanks,

Fab

[lee polowczuk]

yikes..... get the battery charged full with a charger....then let us know what happens. Jumping a dead battery is not a good idea...

sometimtes it blows the OVP fuse as well

[Rob Pruijt]

Driving for 10 minutes is not enough to charge te battery.
A lead battery should aways be as full as possible, the plates go bad very soon is it is empty.
As lee Polowczuk said, get a charger and charge it to full capacity, at least overnight. Depending on the capacity of the charger it can take much longer.
Jumpstarting is a last option, it is bad for the battery and electronics. If you use good quality cables it can be dangerous to.

There are always power leaks, at least one if you have a clock.

Insted of charging the battery I decided to put a brand new one in. After installing it I tried to start the car and the car did not start. I was told to jump it but I thought since there was a new battery I should not have too. I jump started the car anyways and the car started no problem. I took the car on the hwy for about 30 - 40 min. When I got home I turned the car off. 10 min later I tried to start the car and it did not start.

Now the car has a new battery and voltage regulator. Is there anything else I should try?

Thanks,

Fab

[A264172]

Any other circumstances like heavy rain...?

What is the condition of the battery cables particularly the female connector ends?