Seat Belt light Stays on

[mamaya3367]

Hello Everyone,  New to the forum.

I have a 1986 K10 I just purchased.  The seatbelt light stays on all the time with the ignition on.  The buzzer comes on and turns off within 10 sec. but the light stays on.  If I pull the seatbelt the buzzer shuts off but the light stays on.  I've searched the forum with not much luck.  If someone out there has seen this issue please chime in.  I could use the help. Thanks,  mamaya3367

[bd]

What happens if you unplug the black/white wire from the seat belt retractor?

[mamaya3367]

I checked for wiring.  No wiring at the buckle only a black/white wire to the seatbelt by the door.  I unplug it and nothing happens.  No change

[bd]

I checked for wiring.  No wiring at the buckle only a black/white wire to the seatbelt by the door.  I unplug it and nothing happens.  No change

That is the correct wire.  Leave it unplugged from the seatbelt retractor.  Unplug the alarm module from the convenience center located on the interior firewall, above the accelerator pedal and use an ohmmeter to check for continuity between the black/white wire and a good shiny bare metal ground.  Post the results.

[mamaya3367]

I measured the black/white wire to ground.  Showed open.  Turned key to on and still open.  Light stayed on.

[VileZambonie]

Did you try buckling you seat belt? 

[mamaya3367]

Yes, I've buckled the seat belt.  No change. Thanks

[bd]

The seat belt lamp is on with the alarm module unplugged?

[mamaya3367]

Yes

[bd]

How comfortable are you with interpreting wiring diagrams?  From memory, the seatbelt indicator light receives I+ and the alarm module completes the light ground to illuminate it.  If the light glows with the alarm module removed, the implication is a grounded circuit 237 (yellow) wire running between the I/P Cluster PC board and the alarm module socket, or a grounded PC board foil.  With the ignition switched ON, use an incandescent test light clipped to I+ or B+ and probe the yellow wire that connects to the convenience center alarm module socket with the module removed.  Refer to the 1986 factory wiring manual for a schematic diagram that indicates which socket terminal to probe.  Does the test light illuminate?

[mamaya3367]

Thanks for the help.  I am comfortable with reading schematics.  I clicked the link but I'm having difficulty finding the circuit.  Can you tell me which pages to concentrate on?  Also, can you define I+ and B+?  When you say I/P foil pc board is this where all the bulbs connect on the back of the guage cluster?

[bd]

See the attached image and navigate to the 1986 Wiring Manual.pdf page 10.  It is useful to download the wiring manual to your hard drive for future reference.

I+ = ignition positive
B+ = battery positive
I/P = instrument panel
PC board (PCB) = printed circuit board

See Common Automotive (& Shorthand) Acronyms in our Technical Forum for more definitions.

The instrument cluster has a flexible die-cut printed circuit board (PCB) attached to its backside that connects all of the gauges, lamps, and indicators to the dash wiring harness via a 2-row, 18-pin connector.  "Foil" refers to the thin copper circuit traces that wind around the PCB to various locations, each circuit following a separate conductive trace.

On extremely rare occasions, the circuit board traces are not properly indexed with the die-cut of the board.  Consequently, adjacent circuits that are intended to be separate can be cross-connected if the die cut was supposed to sever a circuit trace but didn't quite.  It is a covertly devious fault and difficult to find because the board was manufactured that way so appears unmolested.  Fortunately, this scenario is more common with aftermarket PCBs than OEM boards.

[mamaya3367]

Thank you for the explanation.  I will work on it this weekend.  Stay tuned for results.

[VileZambonie]

Simple diagram

[bd]

Well, that sheds a better light on things.  It's all in the details.