AEM 2G Alternator issues after installing AEM series 1 ECU

[1kick]

Hello can anyone help me I took my 97 gst to get tuned while on the Dyno battery voltage went down to 10 volts so I put a new alternator in after the voltage was at 11.9 when I tested it the next day The voltage was going from 14.8 to 16 The factory ecu controls the voltage regulator the aem does not is there something I need to do to get it working correctly or is it a bad alternator? With the connector plugged into the alt my lights flicker and it stays at a steady 15v would this be caused by the aem ems?

 

[steve]

I don't think the ECU controls the voltage regulator, there is an internal voltage regulator in the alternator. The Factory 2G ECU can control when the alternator charges. (on or off)

If your voltage is swinging around like that I would suspect a bad regulator in that alternator.

 

[1kick]

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So this is the diagram I'm looking at and wasn't sure if the aem ecu was the problem I will try a new alternator and see if it helps thank you

Also if the aem does not have any control do I need to have the wire harness plug to the alternator plugged in

 

[steve]

FR and G are the two new control lines between the Alternator and the ECU. The 2G Technical Manual explains the function of these two new signals (1-73, 1-74, 1-75, 1-77).

FR terminal of the alternator outputs the ON/OFF state of the field coil to the ECU. In response to this signal, the ECU senses the alternator output current, and drives the ISC servo according to the output current (electric load). This prevents a change in idling speed that may otherwise be caused by the electric load. FR is high when the alternator voltage regulator power transistor is off and low then it's on.

G terminal of the alternator allow the ECU to control the alternator output current by duty cycle control of the terminal to ground. When the terminal is not grounded the alternator output is the same as a the prior alternators. When the terminal is grounded the alternator output voltage is limited to 12.3V and since this is below the normal battery voltage very little current flows from the alternator.

Alternator Current Control:

During the period the engine is in operation, the ECU achieves duty control of the continuity between alternator terminal G and the ground. (In this case, the OFF duty of terminal G is controlled to equal the ON duty of the power transistor in the voltage regulator.)
Operation of the headlights causes a sudden increase in current consumption, but the ECU suppresses a sudden increase in the alternator output current, thereby preventing the sudden increases in electric load from abruptly reducing the engine speed while the engine is running at idle. (During the period before the alternator generates enough power, the battery current is additionally supplied to the headlights, etc.)
During the period of approximately 0.5 seconds after the power steering pressure switch has been set to ON and also during the period of approximately 0.5 seconds after the selector lever has been changed over from the N range to the D range, the ECU controls alternator terminal G in terms of 30% OFF duty cycle to suppress generation of power by the alternator.

Under the following conditions, however, this ECU control is not active:

High engine speed.
Engine coolant temperature 50°C or lower.
Air conditioner switch ON.
More than 0.5 seconds after the power steering pressure switch has been set to ON.
More than 0.5 seconds after the selector lever has been changed over from “N” to “D”.
Three seconds or less after the engine has been started.

When a high signal at alternator terminal FR lasting for more than 20 seconds is input to the ECU during operation of the engine, the ECU determines that the alternator terminal FR circuit has been open-circuited and stores diagnostic trouble code (No. P1500), and places alternator terminal G in the always OFF state (Not grounded).