AWR-fix: Valeo Alternaror Refurbish
 

This is not a difficult repair and for the Valeo 120A alternator popular in the 3.0 gas model, it's a bit of a no brainier.

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Here's the basic problem; the one slip ring gets 80-90% off the wear. The matching brush also gets more wear, this leads to too little force/pressure on the contact area and the alternator can't output at low RPM.

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https://www.icloud.com/sharedalbum/#B14JsHvHoGjXxga

My photo album of the repair job. You can find the slip ring kit on eBay or many websites (not Amazon). You can find some YouTube videos with more step by step, I only have some hints at the major steps.

The key thoughts: use heat to remove the epoxy potting if you replace the slip rings. I'm likely to just swap the two brushes and make a no part repair, something I was hoping to do preemptively but wife's alternator decided to crap out before I got a chance.

I figured out a way to swap the polarity of the brushes which will stop the wear of the high wear slip ring and I'll show pictures of the fix.

If you copy the trick somewhere around 4000 hours you should get at least 8000-9000 hours out of your alternator as long as the bearings hold out. (I estimated 5000-6000 hours on mine and wife's before slip ring replace on mine)

AWR-fix: Valeo Alternaror Refurbish
 

So I found some brushes at a local badass old school hardware store and plan to put in some new brushes and swap the voltage polarity rather than swap the slip rings. (which would add a week to the repair).

I'll update wirh photos and I recommend anybody shoukd do this modification about 4-5000 hours and would probably extend the alternator to "lifetime of the truck". (Since 80-90% of the wear is only on one pole of the slip rings). Switch the polarity, switch the wear.

Now that I know how easy the cap comes off the VR I'll see if there is a way to open it and check the condition of the slip rings in place.

Update:

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Photos of the progress. I'll update photo album and captions.


https://www.icloud.com/sharedalbum/#B14JsHvHoGjXxga

alternator back in the car with new holy shit tight belt (I had to loosen the idler pulley to get the belt on).

Perfect score. 13.6v on the battery buss. I don't know exactly where the vBat voltage is sampled but I know that 13.6 is the normal voltage on the OBC.

Sorry I didn't take a photo but the idler pulley between alternator and water pump has an offset center but it has a pin to index where it goes.

By loosening the bolt about 3-4mm it clears the pin and you can rotate the hub and gain maybe 1-2cm of length to get a tight new belt on. Then I was able to rotate the hub back to the proper indexed location.

By the way, don't be a moron and follow all the YouTube videos that tell you to use a T50 to release pressure on the tensioner: the tensioner has a 16mm hex head bump right on the arm for that purpose which is far less likely to slip off and take your pinky finger with it.

Interesting, Andrew!

My slip rings weren't nearly as dirty. I should have taken a picture. Also my top one wasn't that much different than the bottom one. My friend said that the brushes were about half-worn.

The uneven slip-ring wear (one groove deeper than the other) is a common issue. I've seen it on every old alternator I've seen.

Fundamentally, it is due to the positive ions on the positively charged slip ring surface being attracted away, toward the negatively charged brush. Once there, on the one hand, they wear the slip ring more and on the other hand, they left the slip ring, making it smaller.

Conversely, on the negatively charged slip ring, any positive ions that evaporate from the slip ring surface will just hang around where they should be. Slowing the rate of evaporation and not accelerating wear.

Swapping polarity will be a great wear extender if it can be done easily and reliably. Slip ring replacement can be difficult, mainly due to the fragile yet critical field wires that you need to get access to and then connect to.

This has been discussed in bimmerfest E39 5-series forum, which has a nice Valeo alternator rebuild DIY.

Best is to buy Valeo brushes, which are part of the VR when sold by Valeo.

Absolutely correct. I recommend getting the kit with the slip ring and the top bearing. I'd like to see the equivalent for the Bosch.

That said, I did a brush only refresh but swapped the polarity of the brushes so the other slip ring can take over the job off being abused. I plan to do some periodic checks to see how the fix is working.

Update: tested at auto zone today. Passed all three tests I'm plsnning to put back in tomorrow


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Nice work!

I've got some spools of wire that has silicone insulation that would work well in this role - the insulation won't melt when you cross-solder the joints.

We use silicone insulation when wiring battery packs etc. for use in Antarctica - the wiring doesn't get brittle in the cold like normal plastic-based insulations.

Silicone ideal but I just did the soldering while the brushes were at maximum extension so any scar from soldering would not line up.

I also pre tinned the pads with solder and the ends of the wires to minimize the time soldering.

I hope to figure out a way to check in on them maybe in a year or so. I'm considering putting in a window

For checking purposes, most Bosch/Valeo alternators allow you to remove the VR (in which the brushes are part of) in situ w/o the need to remove the alternator itself.

I'm planning to test that theory out. The trick is there is a large plastic cup to direct the cooling air covering the entire back side of the alternator, also the slip rings are nestled in quite tightly So I'm not sure how much you can see until the VR is actually removed

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Although this angle is not bad. Before I put the alternator back in I may remove three cover around there slip rings and glue in a clear window into the air duct.

- That air duct is useless, I removed mine.
- I think you miss my point: in most alternators, you can easily inspect by removing the VR in situ, this process (removal of VR) takes only 5-10 min.

Nope didn't miss point. I was considering removal of the VR only for repair. But: I needed to turn the slip rings which probably was much easier on the bench though running the engine would turn the alternator for me.

With a flex screw driver extension I believe you could remove the air duct cup and VR brush cover in place to get a good view and I plan to do that in a year or so to see if I can see wear on the inside v outside slip ring now that the polarity is reversed.

I did also invent a method to swap the polarity without removing or replacing the brushes. If caught early enough you could nearly double the lifespan of your alternator, probably 70% longer and that should get you 25-30 years on an X5, likely "lifetime".

AWR-fix: Valeo Alternaror Refurbish
 

I doubt you can say that with any degree of certainty. Have you ever measured the temp on your bridge rectifier pack after you started the car with a dead battery and it spends 5-10 minutes outputting 60-80A?

The fins are sideways in back of the alternator and will not get any kind of decent air flow through them without the air cap. Nothing worse than heat on the diode.

I've built circuits that put so much heat thru the drive FET that they literally desoldered themselves (more amazingly without destroying the FET), I would definitely not add more heat shock to the diodes they aren't Incorporated into the VR so much more difficult to replace.