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Completed my Valeo to Bosch alternator conversion

6K views 5 replies 2 participants last post by  bimmerfan620 
#1 ·
I tried posting this in the FAQ forum, but it denied me. Please move to the appropriate location.


Recently, my alternator was showing signs of death. So, after much research on a few BMW forums I found that a few folks have converted their Valeo alternator to the Bosch unit. I even found part #'s for the conversion.

The Bosch, as is, did not fit properly due to the length of the pulley being just a bit too long. However, there is a pulley conversion one can buy to gain the proper pulley offset.

Since I'm nursing a broken leg and torn up knee, I could not complete this conversion myself and had to pay someone to do it (I hate admitting that...). With my Dinan supercharger in place, it took extra time to complete and ultimately, more money.

Most folks might not find it necessary to do as extensive parts replacement as I did, but due to the space my supercharger takes up I didn't want to have to go in there again.

Here are the dealer part #'s:
Bosch 140A alternator 12-31-1-744-567
Pulley for Bosch alternator 12-31-1-432-988
Belt 11-28-1-469-266
Tensioner 11-28-1-717-188

Prior to the replacement, I could only get 13.9V during cold idle, and a little lower during warm idle. With the new alternator, the reading is 14.6V at cold idle. A definite improvement!

The plug-in for the 2 alternator's are identical and required no modification. IF you have a supercharger, a small amount of grinding on the alternator will be necessary for clearance. ONLY if you have a Dinan supercharger.

Finally, I no longer have to deal with the fear of the Valeo alternator leaving me stranded on the side of the road because it decided to die at that time, or replace my battery because I wasn't getting the proper charge to it.

I'm a firm believer in getting information available for other's that might need it, so I hope this helps someone in the future.
 
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#2 ·
yeah, well I just got stranded on the side of the road with my BOSCH alternator.. The damn car lost it's power/charge and just cut out on me... either my ALT is bad, the Voltage reg, DME Main Relay, or the Battery connections... hope I can figure it out..
 
#3 ·
Sorry to hear about your car :( Keep us posted on what you find out about it. It could be either of those items you mentioned. One of the BMW mechanics said that rather than the Bosch alternators just going out, it's usually the regulator which can be replaced. However, that requires tearing your alternator down somewhat, but it will save you some $.

Let us know what you find out.
 
#4 ·
yeah, well the voltage regulator is $60 + shipping, and you have to tear it down, hoping the alternator is still good as well.. i took my alternator to a shop and they tested it, said it was only pulling 0.5V which means it's shot completely... i'm picking up a new unit for $175 at autozone with a lifetime warranty.. all this after they told me it was originally $112 the bastards.... autozone is filled with a bunch of no talent white trash slum buckets
 
#6 ·
yeap, got the new unit installed today, original BMW OEM bosch alternator, and it runs like a champ now... sweet ass deal and only took me about 45minutes to put everything back together...
 
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