Jump to content

Electronic Compass Installed!


Recommended Posts

Thanks to Sahein and others on the board, I sucessfully installed and integrated the electronic compass module that was optional on the '86 to '88 Riviera T Type. It's SOOOOOO cool!

Detailed instructions follow:

I ordered the compass module from GMPartsDirect for like $135.00, part # 1647056.


Remove the black plastic shroud over the brake and gas pedals, center filler below steering column, the floor seatbelt trim, and all door edge carpet edging at the drivers door. I also pulled up the carpeting along that edge, exposing a black plastic raceway which is used for the factory wiring.

While you are under the steering column, drop the central power supply box from it's mount located over the gas pedal, which will bring down the wiring and connector for easier access.

Compass Pinning Info

1 Data Line

2 Data Line

3 7 Volt Power In

4 7 Volt Isolated Ground

I used #14 THHN stranded wire for the installation, as I had it on hand in multiple colors and the stiffness and quality of the wire makes it easier and neater to work with and I taped the bundle together like once every foot with electrical tape.

Was unable to locate the proper connector, so I made individual crimp sleeves to attach each of the four wires to the appropriate connection pins on the compass, compass was mounted on the under the rear window shelf on the drivers' side using industrial heavy duty velcro like the stuff they use for EZ-Pass toll transponders. Wires were easily fished thru from the trunk, without removing any of the rear shelf trim using a drycleaning hanger as a snake. Raceway under the drivers' door opening is hinged to allow you to lay the new wiring in. I snaked the wires up thru the kickpanel raceway and to the area below the steering column where the new wiring splits off from each other.

The 2 data lines were routed to the ALDC connector located just above the emergency brake, connection easily made by removing the connector and using inline taps to the the data wires from behind the connector. The data lines are tan and are the top left 2 wires going into the rear of the connector (it doesn't appear to matter which wire goes to which in the data loop). Power lines were routed up and over the steering column and to the hanging power supply. I unhooked the power supply connector (don't freak everything in the car goes dead when you do this). Looking at the power supply connector, there is a blue and a beige termination stay within the connector, you want the beige set, which is numbered. power to the unit goes into #16 and the isolated ground goes into #7. push the beige wire retainer back into the connector and reattach to the power supply.

Computer Programming Instructions (thanks to Sahein):

1.)Get into diagnostic mode by pushing the climate control warm and off buttons.

2.)Select BCM then BCM override.

3.)Select BS07.

4.)Remember this displayed number so you can return the BCM programming to normal.

5.)Push override up arrow until code 252 is displayed.

6.)To permantly store the new option code: Press and simultaniously hold for more than 3 seconds the GAUGES and OPTIONS buttons surrounding the display.

7.)Turn the key off and then back on.

8.)Select the OPTIONS button surrounding the display.

9.)Compass should appear in the menu. All of the old options are still there but located under a different level.


The compass screen comes up whether there is a compass attached to the car or not, so before you close everything up, go thru the calibration setup on the compass screen (this will involve driving the car in a circle), don't worry about directional accuracy for the moment, just make sure it changes direction when the car does. If the car asks you to point the car north after the circle, congratulations, it is working! hit return to see you compass in action. if the directions change with the orientation of the car you are good to go. Close up all that you have disassembled. Afterwards I recalibrated the compass with a hand held compass to ensure accuracy.

Edited by Rawja (see edit history)
Link to comment
Share on other sites

I installed mine on top of the rear shelf instead of under it. I preferred to hide it completely from sight. The only problem that I had was when I calibrated it. North and South were correct but East and West were reversed. I had to flop the unit upside down to get it to work correctly. It needed to be mounted in the same orientation as if was mounted under the shelf. With the mounting holes up in the air, I decided to put four dabs of clear silicone to hold it in place. It works great and I am happy I did it this way.

Link to comment
Share on other sites

  • 11 years later...

I did this tonight, but found wiring color-code discrepancies between what the electrical manual says and the actual wires. (These were not things mentioned in this thread anyway.)

The only things I wanted to make note on listed here are the blue vs. beige termination stay and data wires:

For both my harness and my spare CPS that has a connector with cut wires, the blue side is the one that contains a #16 wire that gives + 7v ; the beige (actually gray on both of mine) side is around half populated.

The compass module I got used included the factory connector with cut wires, and as shown in the electrical shop manual only pin #2 is used to connect to the BCM (or ALDC as a shortcut in this case, it is all the same UART), so only 1 data wire is needed. While #1 has a pin on the module end, the factory harness only connects numbers 2, 3 and 4. Data, 7V, ground.

I tested it all by rotating the module around by hand and it works good.




Edited by Fox W. (see edit history)
Link to comment
Share on other sites

Good for you! It is a neat feature, however I believe you will have to mount it in the rear. Mine is mounted under the steering wheel and is not accurate. It was one of those things I wanted at the time and is great for showing off to others, but the mirror compass is far more practical...

When I first installed it I would drive in a circle just to watch the compasses on my CRT, Mirror and GPS all change at the same time. How goofy is that?

Ranks right up there with sitting in a lounge chair watching the sequential taillights flash.

Link to comment
Share on other sites


When I first installed it I would drive in a circle just to watch the compasses on my CRT, Mirror and GPS all change at the same time. How goofy is that?
Ranks right up there with sitting in a lounge chair watching the sequential taillights flash.

God... I needed a good laugh this morning!

John F

Link to comment
Share on other sites


Agreed on that last point. Just has so much gee-whiz factor, from a time when such features were truly impressive, despite their questionable usefulness. My only complaint with the CRT compass is the graphic using the back end of a Riviera, and the mountains (hey, I live in Missouri, no mountains here) make it look a little too much like "Pole Position" (the video game). If I ever succeed in decoding the bitmap for the compass screen in the CRTC ROM, I can probably make it more to my liking.

I actually used a 1990-92 Trofeo type compass module - same basic setup but requires only 12 volts in, no 7 volt line from the CPS. I mounted it under the center console storage bin (beneath the armrest) as it is just slim enough to fit between the floor pan center hump and the underside of the storage bin. Seems to loose accuracy sometimes, so maybe I do need to move it to the rear.


Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Create New...