- Joined
- Jun 2, 2012
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- 25,363
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- Location
- canada
- Vehicle Year
- 1994
- Make / Model
- Ford
- Transmission
- Manual
No computer involvement prior to early 2000's for most charging systems.
They are self contained from 2G models and up, 1G had external voltage regulator, 2G has internal regulator.
In your case, when voltage drops with engine running I would test voltage at B+ on back of the alternator, use alternators case as the Ground and then test voltage at the battery terminals.
If B+ shows 12volts then issue is the alternator, it is OFF, for sure
If B+ shows 14volts and battery 12volts then alternators B+ wire is disconnected from truck wiring
Why an alternator turns off can be a few things, all related to the 3 wire connector for the voltage regulator
The Yellow wire is the feedback voltage for the regulator, it tells the regulator the AMP draw of the vehicle, 0 volts here turns off alternator.
White jumper wire connects regulator to stator(field coils), if it is disconnected alternator is OFF.
Green wire is the Battery Light wire, it comes from the dash, it is also the ON/OFF switch for the alternator
When you turn on the key the Battery Light should come on, after you start the engine the Battery Light should go off....IF...............alternators B+ voltage is the same as cab fuse panel voltage, 0 volts here(key on) will turn off alternator
They are self contained from 2G models and up, 1G had external voltage regulator, 2G has internal regulator.
In your case, when voltage drops with engine running I would test voltage at B+ on back of the alternator, use alternators case as the Ground and then test voltage at the battery terminals.
If B+ shows 12volts then issue is the alternator, it is OFF, for sure
If B+ shows 14volts and battery 12volts then alternators B+ wire is disconnected from truck wiring
Why an alternator turns off can be a few things, all related to the 3 wire connector for the voltage regulator
The Yellow wire is the feedback voltage for the regulator, it tells the regulator the AMP draw of the vehicle, 0 volts here turns off alternator.
White jumper wire connects regulator to stator(field coils), if it is disconnected alternator is OFF.
Green wire is the Battery Light wire, it comes from the dash, it is also the ON/OFF switch for the alternator
When you turn on the key the Battery Light should come on, after you start the engine the Battery Light should go off....IF...............alternators B+ voltage is the same as cab fuse panel voltage, 0 volts here(key on) will turn off alternator
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