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Hello!! Hoping you guys can help me track down an electrical gremlin. 2005 Tundra SR5 access cab. The charging system is not working. First indication was the AC fan quit powering on. Put a power source to the fan and it spun so i figured it was the resistor. Then last night it left me sitting on the side of the road. I was thinking the battery was bad since its an 2005 with a toyota battery still on it(I've had the truck for about 2 years). Parts store guy test it says the battery tests bad so I buy that. Runs test again, the alternator is showing failed. So I get that and bolt it on. Kinda a pain in the butt to remove just for the fact its on the bottom of the engine and you have to unbolt the power steering pump to get it off. Anyway, I take the old one back and have them bench test it, it tests good! So I have them test the new one, system still isn't charging. I'm at a loss. My only thoughts are maybe a ground is bad. I've checked the ones on the fenderwells and the firewall, all show as good ground points. Maybe a computer issue?? But I didn't think Toyota's relied on the ECU for charging like that. Any info or direction will be greatly appreciated!
 

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Hello!! Hoping you guys can help me track down an electrical gremlin. 2005 Tundra SR5 access cab. The charging system is not working. First indication was the AC fan quit powering on. Put a power source to the fan and it spun so i figured it was the resistor. Then last night it left me sitting on the side of the road. I was thinking the battery was bad since its an 2005 with a toyota battery still on it(I've had the truck for about 2 years). Parts store guy test it says the battery tests bad so I buy that. Runs test again, the alternator is showing failed. So I get that and bolt it on. Kinda a pain in the butt to remove just for the fact its on the bottom of the engine and you have to unbolt the power steering pump to get it off. Anyway, I take the old one back and have them bench test it, it tests good! So I have them test the new one, system still isn't charging. I'm at a loss. My only thoughts are maybe a ground is bad. I've checked the ones on the fenderwells and the firewall, all show as good ground points. Maybe a computer issue?? But I didn't think Toyota's relied on the ECU for charging like that. Any info or direction will be greatly appreciated!
Have you checked all the fuses and checked the harness in the back of the alt for signal when the key is on




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All the fuses check out good. I did crank the engine and check for volts coming out of the alternator. It doesn't look like its producing.
You have to unhook the harness on the back of the alternator. Should have 3 or 4 wires on it. Then test each one with the key to see if one doesn't show voltage. Most likely that is your problem


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You have to unhook the harness on the back of the alternator. Should have 3 or 4 wires on it. Then test each one with the key to see if one doesn't show voltage. Most likely that is your problem


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Ok, so you are saying to check the volts on the plug going into the voltage regulator. I can do that when I get home from work today and report back. Thanks!
 

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Ok, so you are saying to check the volts on the plug going into the voltage regulator. I can do that when I get home from work today and report back. Thanks!
OK so there is one wire that doesn't show volts. The black and yellow one
 

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OK so there is one wire that doesn't show volts. The black and yellow one
Ok I don't have the FSM wiring diagrams for the 05 tundra on my phone but for the 03 tundra the B-Y wire is trigger from the gauge fuse. But if the gauge fails then your combo meter and all that will stop working

You tested this with the engine running correct?




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Yep, it was the Gauge fuse. It visually looked ok but once i checked for volts on it, it was dead. Swapped out and I'm back to normal. Thanks for the help!!!
 

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Yep, it was the Gauge fuse. It visually looked ok but once i checked for volts on it, it was dead. Swapped out and I'm back to normal. Thanks for the help!!!
im glad i could help. i sent a lot of time with my charge system with my new HO ALT trying to work out a volt spike problem but then one day it just evened out, go figure haha.
 

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Hello all! i have a 2005 Tundra SR5 Access cab 4wd. The exact same thing listed above is exactly what I am dealing with right now. I have done all the above, changed batteries, new alt, 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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