Trailer Hitch & Electronics Install: Paying it Forward

[rcasey]

Following the photos posted by Ranch Hand, and postings by KH, I ordered a hitch and a Modulite electronics module from www.etrailer.com.

These two men helped me, and I thought I might help someone else. This was an easy job on my 08 X5.

My needs for towing are very infrequent. Maybe twice a year, and then for maybe a few hundred miles with two sport touring motorcycles on a light trailer.

Etrailer lists 3 hitches, Hidden Hitch 87455, DrawTite 75600, and Curt 13077. NOTE: the Curt will not allow you to reinstall the OEM steel bumper beam, which is essentially the bumper, under the light plastic fascia. I chose the DrawTite as the Hidden Hitch was on back order. DrawTite and Hidden Hitch appear in the detailed photos and mechanical drawings to be identical. The DrawTite bumper came with decent instructions AND 4 plastic pop-rivets. The supplied pop-rivets are identical to the 4 rivets I’d bought in advance from BMW.

I chose the Modulite 119176, the basic module less tester and less additional wiring. I already have a good VOM tester and 18 gage primary wire on hand.

Removing the fascia was not difficult. Remove the hex head screws as Ranch Hand illustrates.

The easiest way to remove the 4 existing pop-rivets was to lift an edge on the head of the rivet, grip the edge with stout needle nose plies and roll up the rivet head like a lid on a sardine can. The head readily shears itself from the rivet stem and takes about 5 seconds per rivet.

Removing the reflectors was eased by a single long screw driver. From inside the bumper, find the steel flat blade spring that holds the reflector into the fascia, place the screw driver tip on the spring and thump the end of the screw driver with your fist. The reflectors pop out undamaged in one blow.

I’m in southern NM and in 65 degree ambient temps, the fascia was easily un-popped from the dozen or so friction snaps that hold it onto the car. Time to this stage was about 15 minutes.

You will need an 18mm deep socket to remove the OEM bumper bar. Installation of the hitch was simple. Set the hitch onto the 8 M12 studs, set the OEM bumper bar in place and torque the 8 M12 flange nuts to 65 Lbs/ft. As the hitch has slotted holes allowing some side to side alignment, take a few seconds to centre the mount.

The instructions tell you to trim the underside of the fascia 8 inches by 2 inches. This hitch hangs down under the car and does not protrude thru the centre of the fascia like the OEM hitch. The trimming of the fascia is minor and is not visible unless you lay on your back under the car. I trimmed my fascia 8 ½ x 2 ¼ to allow for any small error in not getting the hitch exactly centered.

Installing the fascia was straight forward. Installing the 4 pop-rivets requires a standard pop-rivet tool with a 5/32 inch collet nose.

Installing the Modulite is a simple wiring job. Remove the interior side panels providing access to the tail light wiring. Remove the 6 Phillips head sheet metal screws holding the black plastic panel covering the battery, and remove the panel.

Find the multi pin connector providing power to the tail lights and find the wires at the plug powering the tail lights, the turn indicators, and the brake light. I picked up Brake, Tail, and L+Turn all at the left assembly, and R+Turn at the right assembly.

Unwind the fabric tape binding the wires at the multi-pin connector and working 8 inches below the multi-pin connector, carefully strip ¼ inch of insulation from the identified wires. For the faint of heart, one can use Scotch Lock connectors, but I prefer to solder vehicle connections. In some wet areas, Scotch Lock connectors have failed me, over time. NOTE: stagger your connections a half inch apart. This aids in eliminating potential shorts from one wire to the adjacent wire, and also when re-taped does not look like a python swallowing a pig.

To avoid confusion, buy some primary wire in the same colors as used by the Modulite. You’ll need about 4 feet of wire for each circuit. This will allow you to place the Modulite directly next to the battery and still get the battery cover back in place. BUT, you must position the Modulite DIRECTLY next to the galvanized battery hold down. Text your alignment before removing the paper on the adhesive backing!

Make tidy connections, re-apply the fabric tape to the wire bundles, and make you connections to the Modulite having tested each circuit as you go.

Since my towing needs are slight, I chose not to punch a hole in the floor pan to run the standard flat plug to the trailer hitch. Instead, I followed Modulite's suggestion and when needed, I’ll run the flat ribbon cable out of the underside of the lower trunk lid, over the fascia and down to the receiver on the hitch. When not used, the ribbon cable and plug will be stored between the battery and the spare tire.

The Modulite was accepted by the on-board electronics. No errors have been reported and installation was all well documented by the Hitch and electronics vendors. Hitch took about 2 hours, wiring about 1 ½ hours.


Best wishes,
Dick