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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: mamaya3367 on July 10, 2024, 12:48:01 pm
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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
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What happens if you unplug the black/white wire from the seat belt retractor?
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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
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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.
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I measured the black/white wire to ground. Showed open. Turned key to on and still open. Light stayed on.
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Did you try buckling you seat belt? 8)
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Yes, I've buckled the seat belt. No change. Thanks
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The seat belt lamp is on with the alarm module unplugged?
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Yes
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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 (http://www.73-87chevytrucks.com/techinfo/7387CKMans//Wiring/ST_352_86_1986_Chevrolet_GMC_Light_Truc_Wiring_Manual_CK_10_30_Only.pdf) for a schematic diagram that indicates which socket terminal to probe. Does the test light illuminate?
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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?
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See the attached image and navigate to the 1986 Wiring Manual (http://www.73-87chevytrucks.com/techinfo/7387CKMans//Wiring/ST_352_86_1986_Chevrolet_GMC_Light_Truc_Wiring_Manual_CK_10_30_Only.pdf).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 (http://forum.73-87chevytrucks.com/smforum/index.php?topic=32586.msg276108#msg276108) 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.
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Thank you for the explanation. I will work on it this weekend. Stay tuned for results.
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Simple diagram
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Well, that sheds a better light on things. It's all in the details. :)
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Hello Everyone,
I started probing. With the buzzer module off and I+ on, I have a seatbelt light on. I used a light indicator probe and tested the yellow wire leading to the buzzer. Light on shows power. I'm thinking I have a short in the foil pcb. I don't have another pcb to test so I might need to purchase a new one. Any suggestions?
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Unplug the I/P harness from the back of the instrument cluster. With the ignition ON and the test light clipped to ground, probe the yellow wire at the convenience center again. Does it still illuminate the test light?
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After disconnecting the instrument panel. The yellow wire contact still shows power and seatbelt light stays on.
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:o
Unplugging the 18-pin I/P harness connector from the cluster should disconnect the lamp completely from power and ground. Post pics of the front of the cluster while pointing to the "Seat Belt" lamp. Now, look at the back of the cluster. Does the seat belt lamp location have a socket with two protruding wires plugged in from behind?
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bd,
I need to make a correction. I apologize and thank you for your help and patience.
1. I was measuring the incorrect pin for the yellow wire. I think I have the correct pin now. See picture. With I+ on or off the probe light does not come on for yellow wire. Seatbelt light on
2. I removed the Instrument cluster and switched I+ on and the seat belt light stays on. See picture
3. I found this black box with a pcb in it. The seatbelt light yellow and pink/blk wire go there. If I remove the pcb the seatbelt light turns off. I'm not able to locate the schematic for the circuit.
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You're killing me Smalls!
What engine is in the truck?
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hehehe. Sorry
It’s got the 350.
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I'm not convinced that is the seat belt lamp. Since you have the cluster out, post pics of the back of the cluster clearly showing the PCB so that it fills the frame, while pointing to where the seat belt lamp plugs in. I want to trace the circuit pathways on the PCB back to the cluster connector. Post a pic of the front of the instrument panel while pointing to the location of the seat belt lamp (this is the 2nd time I've asked for this). Also, post a close-up pic of the 18-pin I/P cluster connector that clearly shows the wires exiting the back of the connector. I want to see which wire color enters each connector cavity.
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Here you go. Let me know if this will work.
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There is more to this story. Is this a California truck? Does it have a feedback carburetor?
The pics don't reveal enough. I need to see an unobstructed view with the cluster connector plugged into the back of the cluster that clearly shows the PCB circuit paths from the connector all the way to the seat belt lamp socket. Post one pic with the seat belt lamp socket plugged into the cluster and another pic from the same perspective with the seat belt socket removed. I am very interested in the condition of the copper foils that feed power and ground to the lamp.
Answer the questions posed in the pics below.
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I purchased the truck in Texas with not much ownership history. Not sure if there is a carb feedback. What should I look for? Attached are pictures showing the connections. I did the best I could. Let me know if they will work.
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Happy now bd?? 8)
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There is more to this story. Is this a California truck? Does it have a feedback carburetor?
The 2 bbl carb is something I have never seen in the 100+ C10's I've had. Interesting to me.
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Look at the image below. The yellow arrow points to what appears to be a piece of copper foil that is dislodged from the PCB backing and shifted to overlap an adjacent circuit trace, but the pic is low resolution and isn't clear enough to be certain. I need you to carefully look at the PCB and then describe what you see. Post more pics if needed, but bump the resolution if you can.
The 2 bbl carb is something I have never seen in the 100+ C10's I've had. Interesting to me.
Zieg, if you are referring to 2 bbl feedback carbs, they were used dominantly on the 3.8 L V6's in Caballeros and El Caminos. Virtually all of the V8's with feedback carbs were 4 bbl's - at least in California.
Happy now bd?? 8)
Gettin' there, but my old eyes are struggling... :'(
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bump the resolution if you can
my old eyes are struggling...
No kidding. Are you using a motorola flip phone? ;D
I think you need to send this man a case of beer for this one.
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Look at the image below. The yellow arrow points to what appears to be a piece of copper foil that is dislodged from the PCB backing and shifted to overlap an adjacent circuit trace, but the pic is low resolution and isn't clear enough to be certain. I need you to carefully look at the PCB and then describe what you see. Post more pics if needed, but bump the resolution if you can.
(http://forum.73-87chevytrucks.com/smforum/index.php?action=dlattach;topic=39750.0;attach=55304;image)
In addition to this ^^^^^, please post a pic of the dash instrument panel that sits atop the gauge cluster. I'm looking for a possible alternate home for the lamp that remains illuminated.
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Hello,
I reviewed the last picture with your yellow arrow. I adjusted the copper foil and reconnected the light with no change. I observed the following.
1. The constant on light connector does not have metal prongs to make contact. See picture
2. I'm thinking that this light was connected to the incorrect socket by the previous owners
3. I noticed that there was no bulb connected to the check engine socket. Could this be the check engine light? It never turns off. I would have thought that by disconnecting the battery it would have reset.
4. See the picture of the instrument cluster front bezel.
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Hold a small flashlight up to the upper light sockets in the bezzle. I forgot what mine says in my 85 C20
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Here you go.
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Is it starting to come together and make more sense to you, now?
The 'forever glowing lamp' is the Check Engine indicator; pink/black and yellow wire color codes confirm it. Now you know where it goes. The resolution for the Check Engine lamp can be addressed in a separate topic and thread. In the meantime, remove the air cleaner and snap a pic of the top of the carburetor. I'm wondering whether obvious surprises are lurking in plain sight.
The seat belt indicator uses a twist in socket with integral electrical contacts and a 194 bulb. Temporarily borrow a socket & bulb from an adjacent location for testing. You will need to reinstall the alarm module into the Convenience Center and reconnect the black wire to the seat belt retractor to check the seat belt lamp operation. If it doesn't work correctly then you will need to perform additional diagnostics. You may need to apply some Super Glue between the loose foil and flexible backing to hold the foil firmly in its correct position. Be careful when doing this so that you don't become part of the PCB.
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You will need to reinstall the alarm module into the Convenience Center and reconnect the black wire to the seat belt retractor to check the seat belt lamp operation.
Did they really call it that, or is this a bd snipe/sarc? ;D
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Thank you bd and the rest of the members that helped. I will be putting things back together this weekend and posting a new thread for the check engine if needed.
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Glad to help. Please, let us know how it turns out. :)