by Joe (Rigdonj) » 08 Jul 2002 23:38
Dave said: With the regulator disconnected you will have full output from the alternator. That is the point!!
Sorry to disagree but you're wrong. With either wire or both wires disconncted you should have no output from the alternator. You should have battery voltage on the blue wire anytime the ignition is turned on. The blue wire runs from the ignition switch to both the control module and the alternator and serves three purposes. First it provides power to operate the control module. Second it provides power to the field coil in the alternator. Third, the control module monitors the battery voltage via the blue wire to determine when to activate the alternator. The green wire only connects between the control module and the alternator and it's only purpose is to control the alternator. Whenever the control module senses a low voltage condition it effectively grounds the green wire. That places a ground on the second side of the field coil in the altenator and energizes the feild coil. (Remember the other side of the field coil is connected to V+ via the blue wire anytime the ignition is turned on.) When the field coil energizes the alternator goes into a full outpout mode and stays that ways until the control module senses that the battery voltage is no longer low.
(Insert important point here: the output of all generators and alternators is controlled by their field coils. Apply power to the field coil, or in the case of Chrysler, complete the field coil circuit and the field coil generates a magnetic field. The interaction of the rotating magnetic field and the stationary coils in the alternator creates electricity. End of important point).
In practice the alternator is switched off and on very rapidly under most conditions. Under a light electrical load it's on for less time but under heavy electrical loads it's on for more time.
Note that this is completely different from the way that charging systmes operated when using electro-mechanical voltage regulators. In those sytems there was only one wire going to the alternator (not including the large wire that carries the power back to the battery) and the other side of the field coil was always grounded. In the electro-mechanical systems, the one wire supplied power to the alternator only when charging was needed. In the electronic system, power is supplied to the alternator all the time and the alternator is controlled by grounding the second (green) wire. The electro-mechanical systems also attempted to regulate the alternator output by limiting the voltage on the control wire. Most sytems only used one or two "steps" so regulation was crude. The electronic system doesn't attempt to regulate the alternator output. Instead It's either full on or full off. These systems switch it off and on rapidly to gernerate an AVERAGE voltage on the altenator output.
OK enough theory. Here's how to troubleshoot that problem. First make CERTAIN that both the control module, battery and alternator are well grounded. Unplug both wires from the control module. The alternator output should now go to zero even with the engine running. If it doesn't then there is a short (actually two) in the alternator (or the green wire is shorted to ground but that's not likely). Next short the green wire to ground. That should force the altenator to go into full charge mode. (Don't leave it that way more than a few minutes, it's rough on the battery). If that works then the alternator is almost certainly good. If it doesn't work then verify battery voltage on the blue wire at the alternator. If none then troubleshoot back to the ignition switch and battery. And check the fusible links carefully. They can cause some strange problems! In fact, in this case I'd say that they're the likely source of the problem.* If the battery voltage is good on the blue wire at both the alternator and control AND the alternator works manualy but not automaticly then replace the control module.
* A open or intermitant fusible link will cause the voltage in the electrical system to be lower than the actual battery voltage. The control module will sense that and believe that the battery is low and will therefore turn the alternator onto full output in an attempt to charge the battery. Since the problem is not due to a low battery, the charging circuit will continue to charge at full output until something gives! Carefully check the voltage on the blue wire against the battery voltage. If they're different by more than a couple of 1/10s of a volt then find out why.
PS I just thought of a quick way to check for this condition. Jumper the + side of the battery to the blue wire at the alternator or control module. (You can make this connection before or starting the engine as long as you can safely work around the moving fans, belts etc.) Start the engine. If the wiring is OK then no change in behavior will be observed. But if there is an open fusible link or other wiring problem then this will bypass it and charging should return to normal. Just to be safe, I'd put a 5 or 10 amp fuse in that jumper wire. Otherwise if there's a short in the wiring you could damage something. FWIW I've never seen a problem with the fusible links in Chryslers but I have seen it in other cars and it can cause some real strange behavior.
That should find 99+% of all the charging problems. Let me know if you need more help.