W124 Alternator and Battery

[rrgrassi]

Well here is the update to the belt tensioner issue...

Spring replaced. Belt is happy. But....

At 1500 rpm laternator is charging at 12.8 volts. Took the car to Oh Really for a charging system check. I was told the battery was bad, and VR on the alternator is bad. I am thinking about replacing the whole alternator since it is the original one. I betthe stator is grooved pretty well. In my w123 at 200K miles the stator was pretty well shot.

The battery is an Interstate Megatron II. I do not know the age, as it came with the car.

When I started the car, the ABS light stayed on, until I revved the engine a bit.
So, I will also check the OVP.

Grounding points are clean and tight.

[Diesel911]

You would need another vehicle with a good Battery for this.

Start the Car with the supposed bad battery. Hook up the jumper cables to the batter of the other car without starting the other Car and check the charging rate of the Alternator. Write that down and see if after some time the charging rate does not increase to normal.

If the charging rate returns to normal your Voltage Regulator is OK.

Since the charging system needs to have a good battery to function properly you cannot test the charging system without a good battery.

The little hand held thing that has some resistance coils that the Auto Part places use is not a good Battery Tester. You need to have the Battery charged and then you need a (VAT) Voltage Amperage Tester that has an adjustable carbon pile resistor built into it.
You use the Battery's rating to calculate how much load to put on the battery and set the dial on the VAT to that load. You watch and the voltage is supposed not to drop under a certain amount per the time that the load is on it if the Battery is good.

Note the above test needs to be only as long as is needed ask the Carbon Pile can get burned/damaged.

This site has the one I have but have not used yet. Note the 500 amp carbon pile.
https://www.harborfreight.com/500-amp-carbon-pile-load-tester-91129.html

I have used the similar Military versions of the VAT.

Note that it used to be if you looked closely at the Harbor Fright products you would find access to the instructions in .pdf form that you can download.

[rrgrassi]

Car is up and running again. I took the battery to Interstate, who ran a test in it. Conclusion was needed to be charged. Alternator failed the bench test.

New alternator installed, and battery charged...Also, no more ABS light staying on.