Alternator, pulley removal and fan clutch bearing removal-B5 Passat TDI
Alternator, pulley, fan clutch, bearing removal on VW Passat TDIdifficulty: 2/5
This article shows how to remove the alternator, alternator pulley, fan clutch bearing. Also shown is fan clutch removal for alternator removal. The bearing is also used on Audi.
The alternator charges the battery which provides the electrical needs for the car. The alternator is considered a wear item and should be replaced on an as needed basis only. Symptoms of a bad alternator would be the battery warning light coming on, less than 14V at the battery when the engine is running, or dimming headlights when the electrical load is higher than normal (and you know the battery is good). If the battery is weak, engine rpm when starting can be too slow. The engine computer sees this and does not inject fuel which causes a no start condition.
The most common alternator failures are the alternator pulley and voltage regulator. The alternator pulley acts like a one way clutch. If the bearings or clutch goes bad, the pulley will spin with the serpentine belt but the alternator shaft will not spin at full speed. An alternator is designed to provide adequate voltage at low rpm but a bad pulley will cause low charging and a dead battery. To test it, remove the serpentine belt as described below. Use a wood or plastic pin (to avoid damaging the alternator) to hold the alternator fan inside the alternator. Spin the alternator pulley by hand - you should feel resistance in one direction and none in the other. If it rotates freely in both directions, the pulley is bad.
The other major wear item is the voltage regulator and brushes. The brushes contact the rotating part of the alternator shaft (slip ring) to the non rotating part of the alternator. While the prices of new voltage regulators might be high compared to a cheap rebuilt alternator, the original alternator will be much higher quality than any local auto parts rebuild. Therefore, it's recommended to replace only the voltage regulator if that's all the alternator needs. The alternator bearings are pretty reliable and shouldn't cause any charging problem. The brushes should have at least 5mm movement (6mm is preferable). While the brushes can be replaced very cheaply, it doesn't rule out another problem with the voltage regulator. For voltage regulator repair or further alternator troubleshooting, see 1000q: alternator troubleshooting and voltage regulator replacement.
If the diodes start to go bad that convert the AC to DC you can also lose amperage output and still be at 14V.
The other bearings and pulleys also see wear but they should have long lives if properly tensioned. A loose serpentine belt can also cause the alternator pulley to not turn.
Note: the Bosch alternator and voltage regulator are cheaper than the Valeo. If you have a bad Valeo and it's not an easy fix, it may be worth getting a Bosch replacement. As of this writing, you can find Bosch rebuilds for around $210.
120amp Bosch alternator VW# 028 903 031(x indicates rebuilt). Bosch part number AL0726X
120amp Valeo alternator VW# 028 903 031 a (x indicates rebuilt)
Note: your original alternator part numbers may be 038903018q or 022903199d so check what's on your car first. There are a few part numbers which will fit this car.
voltage regulator for Bosch VW# 038 903 803 e
voltage regulator for Valeo VW# 06b 903 803 b
alternator pulley VW# 022 903 119 d
fan clutch bearing VW# 058 115 136
tools for fan clutch removal
VW tool #3212 or equivalent
tools for pulley removal
Metalnerd tool MN3400set - serrated alternator pulley bit set OR VW tool# 3310 (socket only)
The lower bolt holding the alternator is blocked by the fan clutch so first remove the fan clutch. Also see 1000q: AC serp belt removal for more details.
Fan clutch pulley removal (lock carrier removed for illustration)
Remove the serpentine belt by loosening the tensioner. Use a 19mm open wrench on the tensioner tab and rotate the tensioner to loosen it.
Here is another picture from the front after belt and fan removal showing belt routing. Belt routing is specific to a TDI. The plastic fan is held by 4x 5mm allen bolts.
The fan clutch pulley is held with a 8mm allen bolt through the rear access hole. You must counterhold the pulley to loosen the bolt. Counterhold the pulley using VW tool #3212 (2 pin spanner wrench pictured in Parts) or equivalent. I used 2 allen wrenches through the pulley holes as a substitute and a screwdriver to lever them with a strap wrench on the pulley. Mine was so tight that it bent the allen wrenches so the strap wrench was added. The pulley is pretty thick but be careful to not crush it with too much force with the strap wrench.
If it's still in the car you can use any spanner as long as the pins fit in the holes.
Pictured below is the long 13mm bolt (you can't remove it without removing the fan clutch pulley) and the fan clutch after removal. As you can see, the lower alternator bolt can't be removed with the fan clutch pulley in place. This is why you have to remove it before removing the alternator.
The fan clutch pulley then comes right off. There isn't enough clearance to remove it with the lock carrier in the normal position so just move it to the side if removing the alternator.
Fan clutch bearing removal (optional, replace as needed)
The fan clutch bearing sometimes fails, making a gear/howl noise from the front of the car that goes up and down with engine rpm and not road speed. After removing the fan clutch, spin the bearing to see if it moves smoothly. If not, remove the alternator/ps bracket, (6x 16mm bolts). One of the bolts may be blocked by the thermostat flange/plastic coolant hose.
Use a press to replace the bearing. Some may use a c-clip to hold the bearing so check for them before removal.
Pictured below is the bearing - the 8mm allen bolt goes through it.
First disconnect the battery. Place a rag around the negative terminal to prevent accidental contact with the battery.
Remove the serpentine belt and fan clutch as shown above.
Remove the 13mm nut holding the battery cable, the small plug on the back of the alternator, and loosen the zip tie.
Remove the 2x 13mm bolts holding the alternator and then pry it off. The bushings are holding it tight. When you install the new alternator the bushings will clamp it tight again. Again, you can't get access to the bolts without removing the fan clutch pulley first.
Voltage regulator replacement and inspection
See 1000q: alternator troubleshooting and voltage regulator repair for more details.
Alternator pulley removal only
Remove the dust cap over the pulley if present.
Insert metalnerd tool MN3400 or VW tool# 3310 socket into the splined hole to counterhold the pulley. Refer to the pics above. Then stick the M10 triple square 12 point bit or T50 6 lobe bit through the tool to loosen it. NOTE: The thread is reversed so turn MN3400 or VW tool# 3310 clockwise to loosen it!
To install, tighten the pulley to 48 ft-lb. Below is a video showing how to do this. Also refer to the serpentine belt removal DIY linked at the top.