Hello Everybody,


Working with a 1998 Jimmy with the CS130D alternator. The vehicle has been through 7 alternators in a 5 month period, the longest any alternator has survived is 45 days.


This alternator energizes the regulator with only a single wire connected to the L terminal of the voltage regulator. This wire is not PCM controlled. Key on, engine off and battery idiot lamp illuminated there is 12 volts on this lead. Key on, and engine running and lamp off there is 10 volts. The battery is new, as well as the cables, grounds and alternator 12v out to battery.


Various brands of alternators have been tried. Some never worked out of the box, others worked with 14+ volt output for short periods of time. Every alternator tested good on the bench tester except for the AC Delco unit which lasted 45 days. I believe what I'm experiencing is a voltage regulator failure, or partial failure specifically on the L circuit. The bench testing machines use the S (12v sense) terminal and the I/F terminal to energize the alternator, which as stated is not how it is in vehicle, and they pass.


So far I have replace the regulator plug. I have made a bypass energizer wire with a 12v indicator lamp and 510 ohm resistor. The voltage on this is pretty much the same as the factory setup. I've searched the internet and most of the conversion kits to install this alternator in a non-stock application show a wiring option like my bypass the only difference is resistor values.


Today I was told that the L terminal wants to see a max of 3-4 volts with the idiot lamp on, and that anymore will damage regulator instantly. Well that certainly sounds like it could be my problem, but it doesn't explain the high voltage I see on OE wiring and my own harness built like the one from Painless Wiring.


I'm so confused. I can build a voltage drop circuit using resistors in series and hit the target voltage if necessary. I'm stuck waiting on a replacement alternator anyways, but is it necessary?


Thanks in advance for any input,
Lee