Temperature measured with Fluke IR thermometer.
Voltage measured with Fluke 77.
2000 GM vehicle; Just started; alternator temp: 25 Fahrenheit ; Voltage at battery: 14.3 V idle; 14.3 V Revved
2000 Toyota Vehicle;
Just started; Alternator temperature: 26 F 14.3 Idle; 14.2 Fast idle
Idle for 20 min; Alternator temp 125 F; 14.13 V; 14.13 V revved.
This is the reg for the Bosch altenator in the previous article. CRO setings 5mv/div sweep 1ms/div.
All nine of the diodes are in intimate thermal contact with a heatsink, so they are rated quite a bit higher than you think. The six big ones are rated so that the main alternator output can be 60A, and the trio has to produce the rotor excitation current of 2 to 3A max....
The diode physical size seems to have a lot to do with the current rating, and the diodes i've seen that were 3 amp were much bigger than similar ones that are rated only 1 amp. With that in mind, the diode trio in my alternator has three diodes with body length about one half the length of a 1N4004 series diode and about the same diameter, so they are smaller than a 1N4004 diode. That makes me think they are only rated for 1 amp, but i could be wrong of course as i can not see a number on them.
Various alternators I have measured the rotor resistance is usually between 4 and 7 Ohms.One other interesting thing though is that the driven winding measures 3 ohms with nothing else connected (shaft removed from the alternator and measured directly on the slip rings).
The six larger size diodes used for the main three phase rectification are surface mount and quite large rectangular shaped.
You can buy a generic external VR and modify it to any voltage easily. Just notice if one of the rotor brushes is permanently tied to Gnd or B+, and get either a type A or type B VR as needed.I thought about completely rebuilding the voltage regulator section but im not sure i want to go that route because of the environment it has to run in, under the hood, and im not sure i want to run wires from the alternator all the way into the passenger compartment as that would be about a four foot run.
Granted it would be really nice to be able to adjust it for whatever i wanted it to be.
You would have to retain the brush holder, but disconnect the potted-in VR. That is possible.When you said 'bypass' the regulator, did you mean remove the old one completely and replace it, or just use a permanent fooling regulator that just electrically bypasses the old regulator?
I ask because i cant remove the regulator because the housing also holds the brushes, but i could possibly see using a parallel circuit to the regulator that drives the low end of the coil, and that would effectively take over.
Go back and study the sim I posted way back. The Bosch schematic is consistent with the bang bang method. The switching transistor does not have adequate heatsinking to be a linear regulator. Notice the positive feedback around what is a Schmidt Trigger in Debe's schematic.One more little question, do you know if the coil in these things is driven in a linear way or bang bang just on or jsut off? The linear way would push a very variable current through the coil, which might range from 100ma to 3 amps (or whatever the top end is) while the bang bang would just turn it on and off.
Assuming the bearings are ok (usually replaced at the same time), you can get a new set of brushes inexpensively at the EBay store I linked you to... I have personally rebuilt many alternators. They are easy to get going again...Oh yeah one more thing, the old alternator looks like it has the slip rings all carbonized. I wonder if that is why it stopped working. It worked intermittently for a while before it stopped altogether.
As Mike said, you only have two choices of alternator styles:
1) ground is modulated to the rotor.
2) +12 is modulated to the rotor.
Now, you need access. There were some solder joints on the brush holder. Dunno about the other side.
a) You either move the regulator external.
b) You just override the regulator - bring a single brush terminal external.
It would seem so much easier to design an alternator to modulate ground because +12 ign would be attached to the rotor and controlled by the ignition switch and it gives a relatively low current wire (3 A max or so) to sense the "system voltage".
IF it's the alternator where +12 is attached through the connector to the ignition switch, them you should have continuity between one of the brushes and that terminal. You would then need access to the "other brush:.