Sounds like your alternator is going "full-field" or the LM has lost its reference to ground. The power module drives the field current of the alternator but the logic module is what measures the system voltage and determines how hard to drive the fields. The field terminals are the two small ones on the alternator. One is tied directly to the ASD relay output (battery voltage) and the other is driven towards ground by the PM (the closer to 0V it is, the more current the alternator puts out).
If the driver in the PM has failed (shorted) or the wiring between the PM and the alternator field is shorted to ground or the alternator field has an internal short, the alternator will put out as much current as it can. The battery voltage will vary consistently with engine RPM and the voltage across the two field terminals on the alternator will be at about the same voltage as the battery. If the logic module's ground is floating a few volts above the rest of the vehicle, the charging voltage will increase by that amount. The LM gets its ground through a bolt at the fuel rail. In this case, the voltage across the field terminals will decrease with engine RPM. All that said, it is not good for the electronics to operate at such high voltages for long. Russ On Mon, 2010-07-12 at 21:09 -0700, Malcolm Lawton wrote: > Hi, > Hope you can help me with this problem. When driving, the power loss light > came on and the voltage gauge almost went to 18 volts. I turned on the > lights, heater fan, and rear window defroster. This lowered the voltage and > the power loss light went out. If I turn any of these off, the voltage goes > up and the power loss goes back on. If I remember, the voltage regulator is > part of the computer. Anything I should check before changing the computer? > If I need a new computer, any ideas where to get one at a reasonable price? > Thanks, > > Malcolm > '86 Omni GLHS #044 > > _________________________________________________________________ > Hotmail is redefining busy with tools for the New Busy. Get more from your > inbox. > http://www.windowslive.com/campaign/thenewbusy?ocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_2 > ___________REMOVE-FOOTER-WHEN-REPLYING_________ > ShelbyDodge mailing list > [email protected] > http://www.imagilist.com/mailman/listinfo/shelbydodge ___________REMOVE-FOOTER-WHEN-REPLYING_________ ShelbyDodge mailing list [email protected] http://www.imagilist.com/mailman/listinfo/shelbydodge
