Replacing the Audi ur-quattro's FUBA automatic aerial mast

The FUBA automatic aerial (857 035 509A) fitted to the Audi ur-quattro was obsoleted by Audi in 1997 with no replacement. So much for pieces of paper from Munich. Apart from mast damage, the most common fault is the motor overheating because of a stuck mast, melting the front motor mount and disengaging the worm drive. In such a case the electronics package can be detached from the motor and installed as a simple manual aerial. Note that the white wire must be used to power the electronics - otherwise a continuous current drain will result.

The telescopic mast (857 051 560 - ca. £17) is however still available. If the mast is the only problem with an automatic aerial, it can be repaired.

The instruction sheet is, however, in German only. Although the drawings are clear enough, a translation follows - the numbers refer to the illustrations in the leaflet that comes with 857 051 560:

Items 1-19

Items 31-44

Remove aerial from vehicle:

• 1 - Pull off the power supply cable (14). Unscrew the locking ring (11) and pull off the signal cable (12).
• 2 - Unscrew the locking ring (1) with a 17mm open-ended spanner. Remove the diagonal spacer (2) and sealing washer (3).
• 3 - Release the condensation drain (19). Unscrew the M5 x 20 bolt (8mm head) that holds the aerial to the mounting bracket (8).
• 4 - Pull the aerial out downwards. Remove the contact ring (5) from the stem of the aerial (9).
• 5 - Pull off the power jumper cable (13)

Rebuild the aerial:

• 6 - Open the motor housing (39) by unscrewing the four cross-head screws (32) and removing the cover (31).
• 7 - Remove the white coupling (33) and the black driver ring (34) so that the antenna operating rod (35) is free. Also remove the square white frame (36) with the rod guide.
• 8 - Remove the antenna housing (37) from the motor housing (39) by releasing the two cross-head screws (38).
• 9 - Unscrew the black plastic tip (40) from the aerial mast and pull the mast out downwards.
• 10 - Slide the replacement mast into the housing (37) from below, screw on the new plastic tip, and extend the mast fully.
• 11 - Slide the operating rod (35) into the motor housing (39) and screw the antenna housing (37) to the motor housing (39) using two cross-head screws (38).
• 12 - Lay the square white frame (36) into the motor housing (39) such that the guide pushes the antenna operating rod (35) into the chamber (45).
• 13 - Assemble the black driver ring (34) and the white coupling (33) so that the fit together properly - the tips of the driver ring's teeth must protrude.
• 14 - Lay the driver protrusion on the antenna operating rod (43) in the recess (44) in the white coupling (33).
• 15 - Lay the combination of driver ring, coupling and antenna operating rod into the motor housing.
  
  IMPORTANT! The protrusion on the antenna operating rod must lie correctly in the recess in the white coupling, otherwise the aerial will not operate correctly and the motor housing cover will not fit correctly.
  
  
• 16 - Relace the motor housing cover (31) with four cross-head screws (32).

Replace the aerial:

• 17 - Attach the signal cable (12) to the antenna (10) and tighten the locking ring. Reattach the power supply cable (14) and power jumper (13 - lower contact).
• 18 - Replace the contact ring (5) on the antenna stem (9) and coat the spikes on the contact ring with protective grease (6).
• 19 - Insert the aerial (10) into the mounting hole from below. Replace the bolt holding the aerial (10) to the mounting bracket (8) using a washer.
• 20 - Assemble the diagonal spacer (2) and sealing washer (3), then replace both on the aerial (9). Screw the locking ring (1) on by hand and tighten with a 17mm open-ended spanner.
• 21 - Lead the plastic condensation drain tube through the grommet into the wheel arch, such that between 1cm and 2cm protrudes.

On some cars the condensation drain tube may be connected to the sunroof drain. Whether or not, leaving the sunroof drain detached in the boot may cause water ingress.

If the motor cannot be repaired, the electronic mast is still useful. Dismantle the aerial as above and remove the white operating rod. Reassemble the aerial, detach the single black power jumper, and connect this to the white power wire from the radio. The motor is electrically disconnected. The aerial will now function as a simple manual push/pull aerial, but the electronic function (0db impedance matching) will be retained.

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Contact Phil Payne by email or use mobile/SMS 07833 654800