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Electric issue??


Figgy1227

New Member
Joined
Aug 15, 2020
Messages
2
City
Kennewick
Vehicle Year
1987
Transmission
Manual
So I have gone over all the grounds and all of the wires inside my rig. I have even pulled the alt wires to look at them. I can’t find anything. I charged my battery up to 12.6 volts and then drove with it and watched slowly as the volts dropped back down to currently 12.0 to 12.1. I got the battery tested as well and it is good. I am thinking of replacing alt tmrrw but was wondering if there was any other possible ideas I’ve missed.
 
Check the fusible link
 
There are some diagrams and troubleshooting info in the tech library that could help you. I believe the fusible link dirtman referred to will be orange (16awg)
 
Welcome to TRS :)

With engine running Battery Voltage should show 14.3-14.7volts just after startup, then drop to 13.5-13.8volts after 5 minutes of idling
This is the alternator and voltage regulator working as it should

A car battery is ONLY used to start the engine, after engine is running ALL voltage comes from the alternator, so volts will be above 13.5volts always, this is to keep the battery charged for the next "start up"

To test vehicle wiring
Key OFF
Ground volt meter to alternators metal case

Test B+, its the larger wire connection on the stud/nut on the back of alternator, you don't need to remove it
B+ should show Battery Volts, 12.3-12.8v
If not then yes fusible link is blown or disconnected

Unplug the 2 or 3 wire connector on voltage regulator on the back or side of the alternator
Yellow wire should have Battery Volts, if not same fusible link as above is blown

Test Light Green wire, should have 0volts
Turn Key ON(engine off)
Test Light Green wire again, should now have Battery Volts, this wire is the ON/OFF switch for alternator, its also the Battery Light wire if you have that indicator, and not an AMP gauge

So test these 3 wires, if they test OK and with engine running you don't see above 13.5volts at battery then alternator is for sure bad, not a guess
 

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