Retrofitting OBC

A 13-button OBC is one of the most popular retrofit items for the E30. Exclusive when new, it is one of the first items removed from scrapped vehicles, and as the car ages the value of OBC units continues to rise. While they were primarily designed for M20 engine models, they are also compatible with 4-cylinder models, in particular the dash cluster.

If you want to install one for yourself, here's how.

Parts

• Main OBC unit
• Wiring loom to dash cluster
• Relay control module

Optional

• Outside temperature sensor
• OBC Horn
• Temp sensor\horn wiring loom
• Audible gong
• Remote indicator stalk

Installation

Preparation

Before you begin to think about fitting the OBC, you will need to remove certain things from the car in order for you to access certain areas. First remove your stereo, you will need to use the relevant release keys depending on the make of the unit.

Next remove the lower trim panel above the foot pedals

Now you will need to undo the glove box, unclip the 2 pins that hold it up and allow it to rest in the foot well. Now undo the single cross-head screw that holds the upper trim in place, this is located next to the latch. There are also a couple of plastic screws which require a 1\4 turn to release. Now remove the panel.

Finally you will need to remove the instrument cluster. Learn more about removing your instrument cluster.

Fitting OBC unit

Start off by threading the wiring loom through the dash and guide each plug\connector to the approximate location (as shown previously) ready for fitting. You may wish to clip the loom in with the main wiring loom, this is entirely up to you and will make it look more factory should you or anyone else in the future, decide to remove parts of the dash again.

Now that your loom is in place, you can start connecting the parts to it. It is recommended to fit the actual OBC unit first, this can be quite fiddly and I must stress… do NOT drop the screws that hold it it, you will never find them again if you do!

You will need to release the heater panel in order to make life easier when fitting the unit. Pop out the rear heater switch and hazard light switch and whatever other switches or blanking plates you have there (should be 4 in total). Behind 2 of these you will see a screw, undo these 2 screws taking care not to drop them.

You now need to make use of the stubby cross-head screw driver, beneath the heater panel if you stick you fingers underneath you will feel another couple of screws, undo these and the heater panel should come loose.

There are 4 screws fixing the OBC in place, you will need to use the stubby screw driver again here to do up the 4 screws, I put my hand through the hole for the stereo and did them up this way. Ensure that you fix the green plug to the unit before securing it as it will be difficult to plug it in once the OBC is in place.

Refit the heater panel in reverse of removal.

Relay Module

I would now fit the relay control module. You will need to undo the four 10mm bolts that hold the ECU in place and then remove the plate above the ECU. The relay control module is held in place on top of this plate by two large cross-head screws. Fix the relay control module and refit the plate and ECU, plug the loom into the module.

At this point I would test to make sure that the computer is working, plug the yellow connector into the back of the instrument panel and turn on the ignition to make sure that the computer lights up, it should light up orange and flash the letters UHR. If all is well at this point then continue.

Control Stalk

Next I will explain how to fix the control stalk, this is fairly straight forward. Remove the lower steering column by removing the retaining screws and it should drop down. Next unplug the existing indicator stalk from the main loom and then undo the 2 retaining screws which hold the stalk in place.

You will now be able to swap the stalks over and re-assemble the trim.

Temperature Sensor

Next you will need to fix the temperature sensor into the left hand brake cooling duct, there should already be a place that it plugs into, you will easily see this. You will also need to bolt the OBC horn and cover on, this goes up above where the fog light would be situated, it’s hard to explain exactly but you will know when you see it especially if you removed the computer from another car yourself.

Plug the temperature sensor\horn wiring loom into both the sensor and horn, feed it back along the side of the engine bay clipping it in with the rest of the wiring. You will see a rubber grommet beneath the brake servo, push the end of the loom through the grommet and into the car.

Wiring

Now working from inside the car, attach the two looms together behind the glove box. You will see a main earthing point here which holds several brown wires onto the point with a nut, remove the nut and place the brown PBC earthing wire on the earthing point and secure the nut again.

You should now be left with 2 loose wires, a singe green one and a red with white tracer. These wires simply plug into the main control box, there is only one place that each will fit so you shouldn’t have any problems there.

Reassembly

Finally it’s just a case of reassembling the dash and glove box and re-fitting the stereo.

Article written by E30Adam and copyright to E30zone, must not be duplicated without written permission.

For a fitting guide for lhd cars http://www.r3vlimited.com/tech/obc/obc.htm