My E99's alternator is weak and I need to do something about it. I got a 200 amp alt off of the short bus and I've been scoping it out. I will need to cut back on the existing bracket as I have seen referenced in other posts but it looks like it should otherwise fit. Pulley is same size, bolt pattern matches but the electric plug on the back will need to be changed (I'll solder the plug from the bus harness onto my wiring). The 200 amp alt also has a third wire on it but it only jumps from one place on the alt to another then has two wires going out through that plug so I can't see a problem there, large wire is the same.

Any input, tips or advice on the change out?

And where is that device that holds the tensioner pulley back off of the belt and how is it activated? I can't get my big head in there far enough to find it.

Thanks,
Mark

 

Will it fit in your case? You can clock it to get access to the connections. Consider an external adjustable Regulator.

 

I will fit in there with a little work on the bracket. Clocking of the case isn't necessary as the wires point in the right direction already. Would I need an external regulator? This is something I never heard of before.

 

Need? No.

Want, probably.

The issue with these units is not the Stator / Rotor but the internal electronics. On a rare occasion the windings will ground to the case. But, that is few and far.

The culprits are the OUTPUT DIODES (BRIDGE RECTIFIER / DIODE TRIO and REGULATOR).

I would bet there is nothing wrong with you're unit, its the resistor / regulator fields that fail 99% of the time.

Move them to a cooler area (like the olden days) and failure is greatly reduced.

Any rebuilder can "hook you up" with everything to do the job.


What's nice about an adjustable external regulator is YOU get to adjust it for YOUR needs using an Allen and a meter under load.

The regulator has two inputs and one output. The inputs are the field current supply and the control voltage input, and the output is the field current to the rotor.


The regulator uses the control voltage input to control the amount of field current input that is allow to pass through to the rotor winding.
If the battery voltage drops, the regulator senses this, by means of the connection to the battery, and allows more of the field current input to reach the rotor, which increases the magnetic field strength, which ultimately increases the voltage output of the alternator.


Conversely, if the battery voltage goes up, less field current goes through the rotor windings, and the output voltage is reduced.

Difficulty is about a 3 of 5.