Alternator Replacement

abuck99

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The dreaded battery light came on this week. I'm constantly monitoring voltage output on my scan gauge and hadn't seen any indication that ALT performance was starting to diminish, it literally went south overnight. Went to start in the morning and I noticed the battery light stayed on, I also noticed a "new" constant noise somewhat of a groaning coming from under the hood (sounded more like a weak power steering pump). Isolated the noise was coming from the alternator. Checked battery voltage (engine off) 12.7v (good). Then performed starter voltage test (11.3v)- good. The running voltage output: 12.3 at the terminals hmmm looks like ALT. Anecdotally, cold start was over 13v output but as the engine warmed up, the voltage was slowly dropping to 12.5, 12.4, 12.3.... so more resistance as it warmed up. If the VR was bad, that would reveal itself as high voltage reading (>14.8v)- right? Brushes normally give some warning via diminishing performance over time- not the case here however. And the noise- didn't sound like bearings, more electric load related. IDK. Normally I would buy a $25 brush kit and rebuild, but if it was the VR going bad or bearings its not worth breaking it down to replace when a rebuilt Denso is $113.

2007 with 115k miles; would't think the alternator would fail at this point, but this truck does have dual battery set up, previous owner let it sit for long periods of time and I am assuming that combo maybe has an impact on battery and alternator longevity.

I ordered a reman Denso 210-1100 (07-09 model) from RA for $113 + $75 core charge. It made it me in about 3 days and I proceeded to R&R. Much easier to R&R the ALT on the FJC compared to my 100 Series LC. Less than an hour to remove and reinstall. The most frustrating part was installing a new serpentine/accessory belt- that thing snakes around more pulleys and narrow weird angles under the fan pulley, I swear it took me longer to install that compared to the R&R of the ALT. It's also a good time to inspect and replace pulleys if they are loose or making noise.

Tools: 14mm socket, 12mm socket, 10mm socket and extension, flat blade screw driver or a better tool to gently pry connector, 10mm gear wrench is helpful to remove wiring bracket from ALT.

Steps:
  • Remove battery (for better access),
  • remove tension from accessory belt to remove it from ALT pulley and let belt hang if not replacing belt (14mm socket rotating tensioner towards passenger side-counter clockwise - see image below ),
  • optionally remove intake brace above the ALT (12mm) for better access,
  • remove two wiring harness mounts (one below/beside battery tray called "wire harness stay" 10mm) and the other two are attached to the ALT (10mm),
  • carefully in unclip the female connector on the ALT: tip: release tab is on the right side of the connector- with large flat blade screw driver simultaneously and gently pry/more like twist the blade at the bottom of connector (careful not to crack connector),
  • gently pry the grey terminal cover off, and remove charging terminal cable (10mm),
  • remove the two mounting bolts connecting the ALT to the engine block (14mm). (I used a 20" breaker bar here for better leverage)
  • check the lower mount of the replacement ALT so you can see how it slides out towards you first, then you can squeeze the alternator forward pushing the cooling hose out of the way then upward and out. As you do this be careful not to bump, rub or rest the ALT on the crank sensor wires which are exposed just under the ALT (lay a folded rag over them).
  • Reinstall in reverse order: Torque ALT mounting bolts 32ft lbs, terminal nut 71 INCH lbs (if youre measuring), all others roughly 7ft lbs.
Accessory Belt Install: If your first time installing a new belt- you can remove and install it by sliding over the front of the fan- you dont have to remove the shroud. IDK_ There has to be good start & finish mounting process for this maybe some one can add to this but based on the amount of time I spent I don't think my process was very timely- but I did eventually get it.

Hope this helps any other first timers.


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Thats about when mine went as well. Also, if one so chooses, they can pop in a 130A one from a Tacoma. Direct replacement and nice for a little extra ooomph especially with a AGM battery.
 

abuck99

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Thats good info 👍- I'm still new to this platform. If I knew that ahead of replacing with the 100a, that would have been a no brainer. Same model year range in the taco 07-09?
 
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Sort of. Just the second gen 4.0L. Second gen was 05-15 in Tacomas. I just ordered a 2012 for my 2007 FJ. Its the "tow package" alternator. I think I paid $102 on Advance Auto at the time I did mine.
 

BMThiker

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I paid too much for a 180A model from DC Power Engineering. Didn't realize the Tacoma part was a high output option. This one has been flawless for 6 years though.
2015-07_Alternator (1).JPG

2015-07_Alternator (2).JPG
 

abuck99

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Wondered about those- good to know that they are a reliable option.
 

BMThiker

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For all practical purposes its a 130A product. Peaks at 180A near redline.
1585686712459.png
 

abuck99

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7000 rpm to get 179w lol- The only machine I own that ever sees rpms over 6,000 is my KTM990 😜- I dont think I seldom crest 3000 in my FJ or 100 series.

I like the output current table though- would be interesting to know where the 100A and 130A alternators reach their potential- maybe on a similar scale.
 
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7000 rpm to get 179w lol- The only machine I own that ever sees rpms over 6,000 is my KTM990 😜- I dont think I seldom crest 3000 in my FJ or 100 series.

I like the output current table though- would be interesting to know where the 100A and 130A alternators reach their potential- maybe on a similar scale.

Alternator RPM is not engine RPM. Alternator rpm is normally higher than engine RPM.
 

BMThiker

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I misread that as well - it quite plainly says Alt RPM on the x-axis. Thanks for the clarification @Whiskerz
 

abuck99

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Alternator RPM is not engine RPM. Alternator rpm is normally higher than engine RPM.
Cool- Thanks- you helped me learn something useful today.

I then went down the rabbit hole to find a formula to calculate the RPM and found this: Accurate?
RPM Calculator
An alternator needs 1800-2000 RPM at idle to make power and will make maximum output at 6000 rpm but will fail at 16,000 RPM
Measure Alternator pulley size (for example 2.5")
Measure Crankshaft Pulley Size (for example 5")
The Ratio is 2:1 (5 divided by 2.5 = 2)
To find MAX RPM: take your Max engine Speed (for example 5800 RPM) and multiply it by the calculated ratio (5800 x 2) = 11,600 shaft RPM
To find IDLE RPM: Multiply Idle RPM x Ratio (for example 1000 x 2) = 2000 shaft RPM @ Idle
 
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That looks about right. I learned drag racing years ago that most alternators die in epic ways when spun too high. The big alternator pulley reduces output at idle buts keeps the alternator alive.
 
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