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AL41x alternator upgrade completed!


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A week ago I noticed that even at higher RPMs my voltmeter was only reading 12.7v. I decided to do the AL41x upgrade. I have seen them listed as various amperages, this one came labelled 90A! Found a good rebuild on eBay that came with new fan and pulley + the bonus red painted strip! It's a tight fit but it dropped right in, piece of cake. Here was my method & thinking. Lots of pics below.

 

  1. Disconnected battery (duh), but didn't need to remove it.
  2. Test fit the AL41x and saw that there was ~1/8" clearance between the shaft and the fan blade. It probably would have been fine since the fan should flex away from the alternator but I figured it was easy to add a bit more clearance.
  3. Wrapped the whole alternator in a plastic bag that I poked one hole in then pulled tight around the pulley nut to keep metal shavings out.
  4. I was going to use a cutoff wheel to grind the tip off the shaft, but then decided to go old school and use a hacksaw to keep the heat down and reduce the potential to damage the bearings.
  5. Flipped the black plastic B+ shield upside down on the back of the alternator so that it points in the direction of the wiring loom. I think in the 2002 application the AL41x is mounted upside down from its intended orientation?
  6. Cut the 3 wire head off the harness at the back of the old alternator and installed a female electrical connection on the old blue (now a really faded light blue/gray) D+ wire (there are actually letters on the back of the plastic head to confirm. Taped off the other two wires.
  7. Removed the external voltage regulator from the left inner fender. Left it hanging and didn't cut any of the wires. Apparently the blue wires need to stay connected to each other. At some point when I rewire I will pull the other two wires out completely and wrap up the blue wires in a neater bundle.
  8. Installed the AL41x. It fit nice and snug in the mounting bracket with no shims. Pulled the alternator until the belt was tight and snugged down the adjustment bolt. There now looks to be at least 1/4" clearance to the fan blade and probably more like 3/8".
  9. Installed the B+ wire and the D+ wire. The B+ was easy, but the D+ terminal on the back of the alternator was totally hidden. I got it plugged on there, but it was totally blind. It might be easier to plug it in first, then install the mounting bolts.
  10. Reconnected the battery (duh).
  11. Started the car - "L" light went out immediately and even at a very low, cold idle of around 600RPM voltage was flickering between 14.0 & 14.1 Volts! Mission accomplished.

 

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Edited by man_mark_7
fixed some typos
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I agree, great writeup! 

 

I have a general caution to add, not directly related to your work.  I recently purchased two of the voltmeter/USB units as shown in the photo.  In a bench test with a good digital voltmeter to compare with, one of the two read the voltage correctly, the other showed a voltage 1.6 volts below the actual voltage.  It would still work for relative readings, but worthless in the situation you had.

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39 minutes ago, calw said:

I agree, great writeup! 

 

I have a general caution to add, not directly related to your work.  I recently purchased two of the voltmeter/USB units as shown in the photo.  In a bench test with a good digital voltmeter to compare with, one of the two read the voltage correctly, the other showed a voltage 1.6 volts below the actual voltage.  It would still work for relative readings, but worthless in the situation you had.

Hmm. This spurs me to do a cross check my good Fluke multimeter. I'll report back.

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Nice job!

Looks like the pulley on the 90A is smaller than the stock...therefore spins faster at any given rpm.

Those Webers will make up for the extra power that alternator will draw when you turn on your driving lights 🙂

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14 hours ago, John76 said:

Nice job!

Looks like the pulley on the 90A is smaller than the stock...therefore spins faster at any given rpm.

Those Webers will make up for the extra power that alternator will draw when you turn on your driving lights 🙂

I noticed that. I don't understand it fully, but with the old alternator the adjustment bolt was all the way at the end of the arm. I was wondering if I was going to have to try and swap pulleys or get a smaller drive belt. The pivot points or adjustment arm mount locations must be slightly different because even with the smaller pulley I still have an inch or so of travel now for the bolt in the adjustment arm track.

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  • 4 months later...
On 1/23/2021 at 3:47 PM, calw said:

I agree, great writeup! 

 

I have a general caution to add, not directly related to your work.  I recently purchased two of the voltmeter/USB units as shown in the photo.  In a bench test with a good digital voltmeter to compare with, one of the two read the voltage correctly, the other showed a voltage 1.6 volts below the actual voltage.  It would still work for relative readings, but worthless in the situation you had.

 

I thought about adding the USB voltmeter but have heard complaints of them not being accurate.

Please report back on your findings.  

Agreed great write up,  

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1 hour ago, kine8282 said:

Nicely done and perfect timing as I need to install the AL41X on my car. Do you have a picture of how you wired it all up in the back of the unit? 

It would be pretty hard to get a picture now, the Webers are kind of in the way. I think it will make sense if you re-read item 6 above. There is really only a Battery connection, a Ground, and the D+ wire. 

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