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    Categories: Towing hitch

BMW 8 Series (E31) trailer tow hitch – electrical components

EBA – 01 29 9 783 730
BMW Installation Instructions

All work is shown on a left-hand drive model. Various jobs must be performed in a mirror-image fashion on cars with right-hand drive.

If retrofitted, approval by the official vehicle inspection authority and an entry in the car’s documents may be necessary, depending on local legislation.

When assembling

Use a scraper to remove body sealant and undersea! from all the parts of the car body that come into contact with the trailer tow hitch.

Then clean the surfaces with white spirit. Treat bare areas of the body with zinc powder paint.

When drilling

De-burr the edges of all holes and coat them with zinc powder paint. Remove all swart.

Tools and auxiliary materials required

Flat-bladed screwdriver Phillips-head screwdriver
1/2 inch changeover ratchet
1/2 inch extension
1/2 inch socket wrench insert, 10 mm, 13 mm, 17 mm and 22 mm across flats
Torque wrench
Hammer
Power drill
Twist drill bits, 5 mm and 9 mm dia.
Stepped drill bit, 4 – 40 mm dia.
Rotary miller
Rounded files
Scraper
Vacuum cleaner
Zinc powder paint
Paint brush
White spirit
30 mm-wide masking tape

Cars with airbag

Serial No. llustration     Designation

I                F32 72 075   Special tool

Contents Chapter

  1. Disconnecting the battery
  2. Removing the rear panel cover
  3. Removing the bumper
  4. Removing the car’s towing lug
  5. Removing heat shields from left and right rear silencers
  6. Installing the trailer tow hitch
  7. Installing the tow hitch module
  8. Connecting and laying the additional wiring harness
  9. Installing the socket
  10. Installing the ball head attachment
  11. Installing the repeater light for trailer flashers
  12. Installing the trailer flasher relay
  13. Attaching the adhesive nose-weight labels
  14. Inserting ball head into tow hitch
  15. Functional test

1. Disconnecting battery

F31 72 005

Take out the luggage compartment floor mat (1).

F31 72 006

Grip the recess (2) in left side trim (1) and remove as shown by the arrow.

F31 72 007

CAUTION

Print out the fault memory, as the memory is erased when the battery is disconnected.

The fault memory may be printed out at an approved BMW workshop only.

Unscrew the negative terminal (arrow) and put it to one side.

F31 72 008

Remove the right side trim (1) as shown by the arrow.

F31 72 009

Unscrew the negative terminal (arrow) and put it to one side.

2. Removing the rear panel cover

F31 72 010

Knock out pins (2) as shown by the arrow.

When installing

Recover the pins from the body cavity underneath cover (2), and use them again.

F31 72 011

Lift spreader rivets (1) out to the top.

Fold up cover (2) as shown by the arrow.

Lift cables (3) out of the retaining clips (4) and remove cover (2).

F31 72 012

Unfasten retaining hoop (1). Take out jack (2).

3. Removing the bumper

F31 72 013

Unscrew hex nuts (1) and bolts (2) on the left wheel-arch trim (3).

Remove wheel-arch trim (3).

Note

In the interests of clarity, the illustration shows the rear wheel removed.

F31 72 014

Unscrew the bolts (1) on the right wheel-arch trim (2). Pull the wheel-arch trim (2) forward at the bumper (arrow).

F31 72 015

Unclip the lower section (1) of the bumper at the points in­ dicated by the arrows.

F31 72 016

Push the lower section (1) of the bumper to the side as shown by the arrow, lift it out of the retaining lugs (arrows), and remove.

F31 72 017

Unscrew hex nuts (1) from the contact plate (3) at the left and right of bumper (2).

F31 72 018

With the help of an assistant , carefully pull off bumper (1) in the direction of the arrow.

4. Removing the car’s towing lug

F31 72 019

Take out screws (1). Remove the car’s towing lug (2).

Note

The car ‘s towing lug is no longer required.

The positioning bracket (3) remains in the car ; it is used again when assembling the trailer tow hitch.

5.  Removing heat shields from left and right rear silencers

F31 72 020

Unscrew hex nuts (1) on rear silencers (2). Take off retaining hoops (3).

F31 72 021

Unscrew hex bolts (1).

Remove rear silencer brackets (2).

F31 72 022

Unfasten hex nut (1). Lift out heat shield (2).

6. Installing the trailer tow hitch

F31 72 023

Remove undersea! and body cavity sealant where trailer tow hitch (1) comes into contact with the body at the right and left.

Clean the surfaces with white spirit.

Drill through the pre-formed holes (2) with a 5 mm dia. twist drill bit and open out to a dia. of 9 mm.

Note

Coat the drilled holes and body contact surfaces with zinc powder paint.

F31 72 025

Put on trailer tow hitch (2).

Insert M10 x 25 screws (3) with washers , and tighten them by hand.

F31 72 025

Press on trailer tow hitch (1).

Insert luggage compartment inlays (2) at right and left. Screw on M8 hex nuts (3) by hand.

Align the trailer tow hitch (1) and tighten the screw connec­ tions . Tighten the M10 bolts first.

Tightening torque: M10 x 25 = 21.4 Nm M8 = 41 .8 Nm

7.  Installing the tow hitch module

F31 72 026

Insert fuses (1) into tow hitch module (2).

Note

Use four 7.5 Amp fuses.

F31 72 027

Insert plug (1) into tow hitch module (2).

As shown by the arrow, push in locking slide (3) until it can be heard to click into place.

F31 72 028

Push rubber sleeve (1) on to the tow hitch module.

F31 72 029

Insert tow hitch module (1) into the holder (2) at the rear left of the luggage compartment.

Insert and tighten hex bolts (3).

8. Connecting and laying the additional wiring harness

F31 72 030

Pull the rear light plug (1) out of the left-hand standard wiring harness.

Make the following connections:

Join plug (2) on additional wiring harness to rear light con­ nection (1).

Join rear light plug (1) to adapter (4).

Join 6-pin plug (5) to the tied-back plug connection (6).

F31 72 031

Run additional wiring harness (1) alongside the existing wir­ ing harness on the right-hand side of the car.

Pull the rear light plug (2) out of the right-hand standard wir­ ing harness.

Make the following connections:

Join plug (3) on additional wiring harness to rear light con­ nection (4).

Join rear light plug (4) to adapter (5).

9.  Installing the socket

F31 72 032

Mark point (2) under the left-hand rear light (1) with a centre­ punch, drill it through with a 5 mm dia. twist drill bit and open it out to a dia. of 36 mm.

De-burr the edge of the hole and coat with zinc powder paint.

F31 72 033

As shown in the drawing, run the additional wiring harness (1) through the drilled hole in the rear-end panel as far as the trailer tow hitch.

Insert rubber grommet (2) into the drilled hole.

Using cable straps (3), attach the additional wiring harness (1) to the bumper holder and the lug to the trailer tow hitch.

F31 72 034

As shown in the drawing , insert rubber grommet (1) with plug (2) into holder (3) on the trailer tow hitch.

F31 72 035

Put on socket (1).

Insert and tighten Phillips-head screws (2).

Note

The rubber grommet must lie flush with the socket.

The following components must be installed in the reverse order to that in which they were removed:

rear silencer heat shields, bumper, rear-end panel.

Note

Before tightening the MS nuts that secure the rear silencers to the bearings, press the rubber inner section and bearing bracket 15 mm towards the front of the car (the original loca­ tion should be visible on the rear silencer).

10. Installing the ball head attachment

F31 72 036

Unscrew hex bolt (1).

Remove battery holder (2).

Note

The bolt and holder are no longer required. The battery is held in place by the ball head holder.

F31 72 037

Insert sheet-metal nut (1) into hole (2).

F31 72 038

Insert attachment (1) between the battery and rear light on the left-hand side of the car.

Insert M6 x 25 hex bolts (2) and M6 x 35 hex bolts (3) with washers, and tighten by hand.

Align holder (1), and tighten all three hex bolts. Tightening torque is g Nm.

F31 72 039

Insert ball head (1) into holder (2). Close the lock (3).

F31 72 051

Attach the instructions sticker (1) to the back of the left side trim (2).

Install the right and left side trims .

11. Installing the repeater light for trailer flashers

F31 72 040

Using a small screwdriver , carefully lever out the BMW badge (1).

Release the steering wheel lock.

Turn the steering wheel so that it is pointing straight ahead. Unscrew hex bolt (2).

Mark the position of the wheel in relation to the steering spindle.

Pull the steering wheel off the spindle. Tightening torque is 60 Nm.

Cars with airbag

F34 71 045

CAUTION

The steering wheel may be removed at an approved BMW workshop only.

Using special tool (I), take out the four bolts that hold on the steering wheel.

When installing

Tightening torque is 5 Nm.

F31 72 046

Pull plug (1) out as shown by the arrow and remove the air­ bag unit.

CAUTION

The airbag unit must be set down as shown in in the draw­ ing, with the plug side uppermost.

F31 72 041

Release the steering lock.

Move the wheel until it is pointing straight ahead. Unscrew hex bolt (1).

Mark the position of the wheel in relation to the steering spindle.

Pull the steering wheel off the spindle.

F31 72 042

Take out Phillips-head screws (1). Carefully pull the tr im panel (2) forward.

F31 72 043

Press together the switch retaining clamps. Pull switches (1) out of the trim panel.

Pull off the plugs. Remove switches (1).

F31 72 044

Press together the switch retaining clamps . Pull switches (1) out of the trim panel.

Pull off the plugs. Remove switches (1). Lift out trim panel (2).

F31 72 045

Take out Phillips-head screws (1).

Carefully pull the instrument cluster (2) forward to the steer­ ing column (3) and turn it over.

Note

To prevent the instrument cluster (2) from getting scratched , place a cloth over the steering column (3).

F31 72 046

Insert repeater light (1) into socket (2) on instrument cluster (3) and turn it through goo .

Note

Re-install the instrument cluster and steering wheel in the reverse order to that in which they were removed.

12. Installing the trailer flasher relay

F31 72 047

Fold up catch (1) and remove lid (2).

F31 72 048

Lift out flasher relay (1) and replace it with the trailer flasher relay.

13. Attaching the adhesive nose-weight labels

F31 72 049

Attach the adhesive nose-weight labels as shown in the drawing .

Cars with a nose weight of 75 kg

Attach 75 kg nose-weight label in position (1). Attach “min. 50 kg” label in position (2).

Cars with a nose weight of 50 kg

Attach 50 kg nose-weight label in position (2).

14. Inserting ball head into tow

F31 72 050

hitch Turn locking screws (1) through goo . Remove cover (2).

Insert ball head into the tow hitch and click it into position (see tow hitch operating instructions).

15. Functional test

Connect up the battery.

Hitch up a trailer and check that the trailer lights and flashers are working properly.

Printing and other errors and omissions excepted. Sub­ ject to amendment.

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