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Hello all, hoping someone might have an idea on whats going on with my alternator. This post here gets close to my issue but i still haven't found the culprit. https://www.tundrasolutions.com/threads/charging-system.147134/#post-1633273
I have a 2005 Tundra SR5 Access cab 4wd. I have changed batteries, installed new alternator, had to change Gauge fuse that was blown, checked my battery connections (ground on fender and on block, removed both and cleaned), tensioner is good, and STILL alternator is not charging. I have exhausted the FSM and have run out of ideas. I can actually make the Alternator start charging by grounding the Y-G wire at the EB2 connection. I dont have the Daytime Running Light option. I dont know what else to check. Im assuming the new alternator is well grounded after bolting in place. Anyone have any ideas??
 

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I would have to get into TIS myself to look at the connections and control. Is the Y/G supposed to be a ground? If yes follow that to a good ground to find the problem.
From what i can tell on the electrical drawings, it would complete the circuit to ground if the generator IC regulator has an issue. I do read 10.something volts in the connector at the alternator end. Could this be too much residual voltage to keep alternator from turning on?
 

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Update: Found brand new alternator, AC-Delco brand purchased through RockAuto, would not switch on. When you first turn your key on you should have a Battery Light ON indicating the alternator is not charging. But what this also indicates is you have a complete circuit from the battery light, through the internal circuitry inside the alternator, then to ground. I DID NOT have this Battery Light ON with this new alternator installed. I checked all 3 wires that go down to the alternator to make sure they were working as they should. So, the problem was pointing at the brand new alternator, which was hard to believe. The battery light circuit could not find a ground through the alternator thus not allowing the alternator to switch on. Out of curiosity, I unbolted the new alternator, took my old alternator and just worked it up in among all the hoses to where it would just sit there. Hooked up the 3-wire connector and used jumper cables to ground the alternator to the chassis. Hooked my battery back up, turned on the key, BAM!! Battery Light came on! I ended up bolting my old alternator back on. All works perfect.

My issue this entire time was actually just a blown gauge fuse. I guess i missed this fuse when i was checking all the fuses. One thing led to another, thinking my alternator was actually bad.

What blew my gauge fuse was a mis-wiring on a trailer 7 blade hook-up. After doing some checking, the center blades on the trailer plug was actually wired to ground. The center blades are supposed to be reverse lights. So what happened was after the trailer was hooked up and I was putting the truck in to Drive, as soon as I hit the Reverse it blew the gauge fuse.
 
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