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Discussion Starter · #1 ·
So I am trying to do a lot of PM to my daughters 2003 NB Convertible GLX because it is going about 1100 miles away and I will not likely see it for 2 years, assuming it lasts this long!

So one of the MANY PM items I decided to do at the last minute was to replace the Voltage regulator on the alternator. Initially I thought this was going to be fairly easy to find, however, it appears these cars had a number of different alternator manufacturers AND Amperage outputs.

Seems like many German cars have either Bosch or Valeo alternators. Then trying to figure out how many Amp the unit is the next challenge.

Went to the dealer figuring I was short on time and the would be able to get a regulator quickly. Well this did not work out so well. The dealer parts guy was very good and tried his best. After looking up parts by VIN, still this did not narrow down things well. Then the parts guy looked up the build options and found out my car came with a 120 Amp alternator. I had figured out it was a Bosch based on the name embossed in the rear plastic insulator plate.

This is where the fun begins!!

So there appeared to be a few different Amp Bosch units listed and regulators were shown as available. However, there was no regulator available for the 120 Amp alternator listed in the parts catalog.

So what to do. Well the good parts guy suggested I look for part numbers, VW does a GOOD job marking almost everything with part numbers, assuming paper labels stay on the part and are not damaged by grease or cleaners.

I was able to stick my phone down behind the alternator and use the Macro function and take some pictures of the Voltage regulator part number as well as verified the alternator was in fact a 120 Amp units. I was able to find the Bosch Voltage Regulator part number as well. My car had a Bosch Voltage Regulator part number F 00M 145 261. So I started my search. Found a few hits on ebay, many were for Asian clone/knock off units that I had no interest in, then I found a decent listing for Bosch OE regualators with some part number crosses. I finally settled on a F 00M A45 303 regulator for $65, which was over 1/2 of what the dealer was tanking about. Not exactly what the differences in the Voltage regualtors, but my car is not charging at around 14.2 Volts vs. the original 13.85 Volts.

Regulator arrived today. Looked it over to see how it was mounted, really did not want to pull the alternator as it is kind of a PITA, more just getting the belt tentioner moved due to hoses and so forth. Realized I would also need to remove a plastic insulator plate from the rear of the alternator as well.

DISCONNECT THE BATTERY BEFORE YOU START!!!!!!

Well I ended up pulling the dipstick tube and bracket, draining the coolant and removing the lower radiator hose from the thermostat housing. Also had to remove the lower cable clamp on the alternator as well. A few Phillips screws, used my 1/4 drive flex head ratchet (love this tool!!!) and a 1/4" socket and some 1/4" Phillips bits from one of my screw drivers.

After the lower radiator hose was off, about 15 minutes later the new regulator was installed. A few hex nuts, 13mm for the battery cable and 15mm for the larger Voltage regulator nut, 4 Phillips screws, a connector and after removing the lower cable bracket, I was able to get the plastic housing off the rear of the alternator all while it was still mounted in its original position.

I also used compressed air to blow out the slip ring area as there was some brush debris in the slip ring portion of the alternator. Reversed the order of screws, just make sure the shorter Phillips screw with washers needs to go on the lower side of the Voltage regulator.

I can tell you the replacement regulator has VERY long brushes compared to my originals. I guess my alternator my have lasted another 20k miles, but who wants to push the envelope. I am trying to make the car as reliable as possible at this point.

See pictures of worn brushes in the old regulator vs. the new regulator. Notice the length of the brushes and also notice how one brush is worn more than the other. Seems the brushes are about 2/3 worn at 96k miles.


Highly suggest a PM regulator by 100k miles, not very hard to swap out, the 1.8t probably has better access than the other engines. While it would have been slightly easier to pull the alternator and just roll it in the engine compartment, I found replacing the regulator was fairly easy with the right tools and game plan.
 

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I have been anticipating this issue; on my car for awhile, in my case the alternator is a 120 AMP Valeo , instead of a Bosch. Bosch sells a replacement for the the Valeo version; so, that is a option. Researching online; there are sites, that sell regulators or whole rebuild kits with bearings, brushes/regulator and new slip rings. I guess with anything; it depends on if you want to spend the time doing the rebuild process yourself or just swapping it out for a rebuilt unit. This would be something to consider; if the bearings, clutch pulley or other parts are bad, aside from the just the brushes. I was thinking; it might be fun to rebuild the alternator, as long as a rebuild kit is cost effective and there are quite a few videos on youtube, showing the process. Here is a page; going over the brush replacement, on the Valeo alternator.

http://www.audizine.com/forum/showt...lternator-Fix-replacing-brushes-(Valeo)/page2

After your regulator swap; did your charging volts improve at all? I'm thinking; that my charge wire, might need to be replaced as well. I'm wondering; if the resistance in mine has increased from corrosion, I guess a voltage drop test would confirm that issue. My voltage has been jumping around from 12-13.5 volts lately; that seems to be low compared to what others are say is normal. What is your voltage now?
 

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Discussion Starter · #3 ·
My charging Voltage did improve, not sure if this was due to the regulator or not. There was some vague reference to the fact that different regulators had different charging Voltages?

I recall that before the regulator change the charging Voltage was around 13.85 Volts, after the change I think it was around 14.3 Volts. BUT this was measured with my UltraGauge that is monitoring the Voltage at the OBDII port.

I did find that the nut for the output wire was a bit looser than I would have expected, however, no sign of heat build up or over heating. I torque the output nuts pretty well by hand. Again, my 3/8" and 1/4" flex head ratchets and my 1/4" wobble extensions are by best friends!!

I decided to leave the alternator in place and things worked out well, I had to be slightly creative, remove the lower radiator hose from the stat housing (drain) the cooling system, but I think this was faster and easier overall.
 

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automotive elctric shop

I had stated this in another thread before that there are automotive electric shops out there that will replace your alternator's internal voltage regulator(that's their specialty) for a situations like this when folks only want to replace the regulator and not the whole alternator. Most of the time that's usually what go's wrong the winding hardly ever go bad.
 

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Discussion Starter · #5 ·
1400 miles of regulator, all seems to be working fine. Not 100% sure but I think it is temp compensated????

I am in an area 40F warmer than when I installed it and charging Voltage is in the low to mid 13's. Not so worried as for the 1200 mile trip I watched the charging Voltage VERY close with my Ultra Guage and all was good.

Not sure why you would have a shop replace the regulator as it can be replaced on car, just need to remove the lower radiator hose from the thermostat housing and the dipstick tube. About 6 bolts/screws.
 

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When you reference; temp compensated, are you referring to the charging system or something else? Your charging numbers; are similar to my Valeo 120 amp alternator.


Sent from AutoGuide.com Free App
 

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Discussion Starter · #7 ·
The Voltage regulator seems to be temp compensated. Seems to charge at slightly below 13.5 Volts in the new temp environment, had 96C Temps yesterday. BUT this is as shown with the Ultra Guage which is monitoring the Voltage @ the OBDII port, not as monitored @ the battery. The entire 1100 mile trip the Voltage was around 13.8 Volts, but the Temps were under 80 F.
 
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