Charging

[Jakob F Prasz]

Hey everybody

I have major problems with regards to teh charging system in my 230CE 1990. I reasently changed the alternator to a 55amp new one, but it didn't deliver more then about 13 volts. I was then told that it was because that 55 amps is not enough, so today, after it had drained the batt. I got the "old" 55 amps switched with a new 70 amp one, but the problem is the same, it only delivers 13-13,8 volts, and as soon as i turn on the headlights it drops to aprox. 12,7 volts. I'm lost here, does anyone have a good idea about what could be the problem?

With kind regards
Jakob

To begin with it doesn't matter if it's a 55Amp alternator or a 75Amp alternator. On either one the voltage regulator should keep the voltage at 13.8 to about 14.5 volts unless the battery or accessories are in the act of DRAWING lots of current.

Use a digital voltmeter or very sensitive analog meter and measure the voltage drop from the connector at the alternator to the positive post of the battery. If it is more than just a few tenths of a volt you have a bad connection along the way.

Also use the voltmeter to check the voltage drop between the alternator case and the negative battery post. This one should be zero.

If you have too much voltage drop anywhere fix those connections. If the voltage drops are normal then you must have something drawing LOTS of current and you need to put a hefty ammeter in series with a battery cable and its post to see how much the draw is and then disconnect things until you find the culprit.

Good luck,

[Jakob F Prasz]

Hey Larry,

I did check the connections, and i measured about 0,1 volts between the alternator case at the chassis. I didn't think that it could be a problem, but I will clean/change the ground wire from the engineblock to the chassis tomorrow, thank you for that info.

Jakob