voltage regulator

[joshua dewitt]

the 70 and later 2 in style voltage regulator.... the ignition field center, the green wire field negative outer, but the casing of the regulator is supposed to be grounded, now, is the field negative green wire terminal on regulator supposed to have continuity to the regulator case itself with ohm meter?

 

[67Dart273]

"Probably." I've never checked. I assume you mean the disconnected regulator is what you are describing

With the field wires disconnected, NEITHER alternator field terminal should show continuity to ground. That is why it's properly called "isolated field."

The way it works is that there is a big transistor in there that for lack of better, controls the "amount of ground" on the green wire. That is the field receives 12V on the blue field wire, goes through the field, and the regulator completes the circuit to ground, and controls that

For the purists, of course, electron flow is opposite direction, but above is the complete 'path'

 

[AJ/FormS]

I would imagine that, since the VR is grounding the field coil through it's case, there would have to be a connection thru there(green to case). I imagine the transistor is switching from Full continuity to Zero continuity in response to what it sees the system needing.

Now the Chrysler engineers could design the circuit to fail in either full fielded condition or full open condition.
But since you almost never hear of a a battery being cooked and the headlights being blown out; but you do hear about lots of "fails to charge" conditions, I'm betting on it's failing in full open condition.
To my way of thinking then, with the VR out of circuit, there should be little to no continuity from the terminal "green" to case ground.This means the ohmeter should read open circuit to very high resistance.
'Course my thinkin' has been wrong on many occasions.That's part of learning.
The big question is; Why do you ask?" Inquiring mind or charging problems?

Merry Christmas!

 

[KitCarlson]

Using a multimeter on continuity test may lead to uncertain results. The continuity threshold is typically 40 Ohms. There is a diode check on some meters, it measures the forward drop of diodes if leads are connected to forward bias juntion. This is mentioned because mosfets have an intrinsic diode, and a flyback diode is in the circuit to shunt the field, protecting the transistor from inductive kick.

Transistors are rare to fail, but the most likely failure is shorted. To fail open requires huge current to explode the die. Since field resistance limits the current to about 5A, that may not happen unless the field is shorted, or 12V applied without field.

A good way to damage a regulator is intermittent ground or field connection. The field has significant inductance, when opened the inductive kick results in hundreds of volts. The volts are applied in an abnormal manner, outside of normal operating and protection means. Yes some might survive.

Here is good information on regulator circuit design, page 7 is most interesting.

 

[nm9stheham]

I seriously doubt that the output driver of the original regulators would be a MOSFET.... since they weren't in existence or at least in common production then. The new parts? They could very well be.

As said, using an ohmeter on the regulator output to ground is unpredictable; it depends on the exact design, and even on how the meter is used and what polarity is used. There might be a couple of 'most common' designs...

 

[67Dart273]

Most probably because "I grew up" with old analog meters, when ohmeters were not that accurate, I tend to depend LESS on resistance readings unless "I'm down to that." There are no published resistance check specs that I'm aware of for these regulators, therefore I don't try to make any.

I wish the OP would come back and explain what he is trying to accomplish