One evening in January 2011 my boiler started to make a loud whining that sounded like the motor bearings had knackered out.
So I took it to bits and replaced the motor bearings. It was fairly straight forward.
The motor is a AEG EB95 C35/2.
The bearings in the motor were 6202.Z and 6001.Z. I replaced them with .ZZ bearings. I think they are the same.
I ordered from http://budgetbearings.co.uk

1 6202.ZZ.EU 6202ZZ Budget Metal Shielded Deep Groove Ball Bearing 15x35x11mm £2.29
1 6001.ZZ.EU 6001ZZ Budget Metal Shielded Deep Groove Ball Bearing 12x28x8mm £2.29
Items Sub Total: £4.58
Shipping Method: (Royal Mail 1st Class Post): £1.50

VAT: £1.22
Order Total: £7.30

1. Unplug the heater from the mains electricity or unplug the power cord near the top of the door
2. Remove the heater unit from the boiler by loosening the two screws and sliding it out. See http://www.stevematt.f9.co.uk/heater/page6.htm
3. Undo the two screws holding the motor in place and pull out the motor.
4. Check the motor spins freely. It may not if the bearings are knackered.
5. Slide or lever off the white plastic gear. This is made of a soft plastic. Be gentle and take care not to damage this gear, getting a replacement might be very difficult.
6. Make a note of the spacing between the fan and the motor body. Using a 4mm allen key loosen the screw holding the fan. There is a hole in a fan blade which may be covered by a sliding cover.
7. Take out the four motor housing screws.
8. Pull the motor apart. Watch out for a spring and flat washer in the end bearing housing.
9. Holding the motor rotor and the fan, rotate and twist off the fan.
10. Check the bearings by: Spinning the bearings on the shaft. Spinning the shaft holding one bearing at a time. A worn bearing might not spin freely.
11. Pull off both the bearings with a puller. They come off fairly easily.
12. Read the bearing numbers from the side of the bearings.
13. Order new bearings.
14. Gently tap the new bearings on to the shafts. Rest a spanner or tube against the inner ring of the bearing and tap that so as to avoid tapping the outside of the bearing.
15. Insert the motor rotor into the end plate and slide on the fan. By holding the motor rotor and turning the fan back and forth when tightening the grub screw you can make sure the fan aligns properly with the flat on the shaft. Make sure the gap between the fan and the end plate is the same as when you started.
16. Re-assemble the motor. Remember to install the two washers in the end bearing housing.
17. Carefully push the plastic gear onto the fan hub.
18. Check the motor spins freely.
19. Carefully re-insert the motor being careful not to damage the plastic gears.
20. Tighten the two motor screws.
21. Re-insert the unit into the boiler and tighten the two retaining screws.
22. Check that all the wiring is routed away from the boiler and other hot areas.
23. Plug the power cable back in.
24. Test the boiler making sure the motor starts ok.