Author Topic: 86 K10 lighting issues  (Read 13029 times)

Offline mdfiore

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86 K10 lighting issues
« on: September 26, 2012, 07:53:04 AM »
Hey guys, I'm starting to put my interior back together on my 86 K10 and have a few issues with the lighting.  I can't seem to get the front marker lights on the fenders to work at all.  I have 12 volts with the light switch on, I replaced the bulbs and still have nothing.  They also don't flash with the turn signals.  Grounds on the radiator support are all clean and hooked up.   I also have a problem with the turn signals which may be related.  With the ignition turned on if I turn the turn signal both signal lights on the instrument cluster flash as well as the tail lights and the front signal lamps behind the grill.  If you then pull on the light switch they quit blinking.  I can't get just one side to blink.  I'm just not sure where to start.  Please help.  Thanks.
1986 Chevrolet k10 Silverado.

Online bd

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Re: 86 K10 lighting issues
« Reply #1 on: September 26, 2012, 11:45:45 AM »
First inclination is toward grounding issues.  Sounds like you have a "floating ground" where multiple circuits share a common grounding point that isn't, in fact, a good electrical ground, because of paint, corrosion, dirt, a missing or broken ground cable, and so on.  Could be at the front, rear or any part of the vehicle. 

Make up a test jumper that connects directly to the battery negative terminal, then touch various strategic bare metal spots around the vehicle (e.g., radiator support, frame rail, engine block, cab body, fenders, bed, etc).  There may be more than one ground problem.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline zieg85

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Re: 86 K10 lighting issues
« Reply #2 on: September 26, 2012, 03:05:40 PM »
Just a thought... does your 4 way flashers work?  If not your 4 way flasher switch button may be pushed in which what you are describing would happen.
1985 C30 Custom Deluxe Ext. cab 5.7L TH400 3.21 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
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Offline mdfiore

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Re: 86 K10 lighting issues
« Reply #3 on: September 26, 2012, 07:12:40 PM »
If I push the four way flashers with the key off rear lights and front lights behind the grill flash but no side marker lights.  If I turn the left signal on the rear blinks but nothing in the front.  Turn the right on and it acts like the hazards are on.  I'm still checking all the grounds but so far everything is grounded.
1986 Chevrolet k10 Silverado.

Offline mdfiore

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Re: 86 K10 lighting issues
« Reply #4 on: September 27, 2012, 07:49:14 AM »
I have power at the side markers with the light switch on so apparently its not getting a ground somewhere?  Where do the side marker lights ground?  Through the switch?  From the wiring diagram it looks like the blue wires go into the column and hook up to the signal switch.  Could this be bad?  Maybe the turn signal flasher is bad? 

I ran jumper grounds from the firewall to the batterie neg. terminal.  From the Bed to the frame. and still the problem exists.  This is really frustrating!
1986 Chevrolet k10 Silverado.

Online bd

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Re: 86 K10 lighting issues
« Reply #5 on: September 28, 2012, 01:05:31 AM »
...Where do the side marker lights ground?

The forward, side-marker lamps employ a clever bit of engineering.  Each side-marker is powered through one of its two wires by the park lamp circuit.  But, each side-marker is also powered through the other of its two wires by the left (or right) turn signal circuit.  You ask, "How do the side-markers work if they have two power wires and no ground?"  Good question.

* To follow this explanation, keep in mind that each front park/turn lamp assembly has separate park and turn filaments with dedicated power wires, but share a common ground wire to the radiator support.

* When only the park lights are ON, the side-marker receives constant power on one wire from the park light circuit and 'grounds' through the turn signal filament of its respective turn lamp (left or right side), so the side-marker illuminates continuously.

* When only a turn signal is ON, the side-marker receives 1-second pulses of power on the wire from its respective turn lamp and 'grounds' through the combined filaments of all the park lamps, so the side-marker flashes in unison with its respective turn signal.

* When both the park lights and a turn signal are ON, the side-marker receives constant power on one wire, while it is alternately 'grounded' through its respective turn signal lamp when the turn lamp flashes OFF, and then powered on both wires at the same time when the turn lamp flashes ON, so the side-marker flashes alternately with the turn signal as the 'ground' appears and disappears.

So, in fact, neither of the two wires running to the forward side-marker lamps are "ground" wires in the sense that we normally think of ground wires.

Back to one of your original questions...

...I can't seem to get the front marker lights on the fenders to work at all.  I have 12 volts with the light switch on, I replaced the bulbs and still have nothing.  They also don't flash with the turn signals....

Perhaps you've lost connection between the side-marker lamps and the front turn lamps.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline mdfiore

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Re: 86 K10 lighting issues
« Reply #6 on: September 28, 2012, 07:01:11 AM »
Well after three nights of testing wires, cleaning and checking all the grounds, tearing the steering column apart...twice, replacing bulbs, and pulling out my hair, I'm happy (and angry) to say I found the problem.  Turns out that I had 1156 bulbs in the front running/turn signal lights behind the grill instead of 1157.  Grr... So the single terminal on the end of the 1156 was touching both contacts in the bottom of the socket causing the running lights to be on and blink but not the side markers.  Sometimes I guess the simplest answer is usually the correct one.  Thank you to all who have replied.  Hopefully my idiocy will help some one else out if they ever have that problem.
1986 Chevrolet k10 Silverado.

Online bd

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Re: 86 K10 lighting issues
« Reply #7 on: September 28, 2012, 09:59:13 AM »
...Sometimes I guess the simplest answer is usually the correct one....

That should be framed   :)
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)