side marker lights - The 1947 - Present Chevrolet & GMC Truck Message Board Network

camarohair · 10-11-2016, 06:09 PM

hi folks,

let me start by saying that i'm not at all good with electrical trouble-shooting, but am not afraid to try! I've read up on some other threads and am not sure that i've found the answer to my problem.

i've got a '68 C10 that someone set-up with working side marker lights. The front driver side marker light won't come on solid with the parking or headlights (the rest do), but the side marker turn signal does work whether or not the headlights/parking lights are on or off. every other light works as it should, including turn signals all around, it's just the one light that won't come on with the headlights or parking lights. i've replaced the bulb and the entire housing/socket. what steps should i take to figure this out?

thanks in advance for the assist!

custom10nut · 10-11-2016, 06:24 PM

If your side markers flash at all, somebody tried to retire them to do so. The should only come on steady when your running lights or headlights are on. What do you back ones do when you use you turn signals? I'm curious to see where they found a dual filament bulb that size.

LongBox · 10-11-2016, 06:32 PM

To make the front side marker lights blink with the turn signals, the ground for the marker light goes through the signal light and socket. Someone may have tried to rig this up this way, and someone else on the board may know how to get it to work properly. If it was me, I'd carefully clean up the front parking/turn signal light socket, make sure it is grounded properly, and that the bulb is good.

jescates · 10-11-2016, 06:32 PM

Sounds like it's not grounded. If you have a voltmeter, you could remove the bulb, turn on the lights and put the red lead inside the socket and the black lead on the frame and see if you have 12 volts. If you do, then you have lost a ground to that light!

**dmjlambert** · 10-11-2016, 08:01 PM

Here is the schematic for 3 different ways of connecting the front side marker, in this post
http://67-72chevytrucks.com/vboard/s...=707545&page=2

Use a voltmeter to explore and figure out what voltages you get, and also just examine the wiring to see how it is hooked up and compare to the schematics on that other post.

The front parking lamps have 2 filaments. The dim filament is for parking light, and the bright filament is for turn signal. The parking lamp housing must be grounded to complete the connection for either of those filaments inside the bulb.

The side marker light uses one filament to do both jobs. There are 2 wires going to it, and no housing ground. Even with the front parking/turn signal completely disconnected or not grounded, the side marker light should still work (it does on my truck).

I think it is likely your front driver side marker light is wired for blinker only, and the front passenger side is wired for combo marker and blinker.

The combo marker and blinker wiring for the side marker light is not compatible with LED bulbs. As far as I know it must be a regular incandescent 194 bulb. It is possible there are LED bulbs that are not polarity sensitive, so those may work but I have not heard anybody talking about those and I have regular incandescent bulbs.

10-11-2016, 06:09 PM	#1
camarohair Registered User Join Date: Sep 2016 Location: phoenix Posts: 2	side marker lights hi folks, let me start by saying that i'm not at all good with electrical trouble-shooting, but am not afraid to try! I've read up on some other threads and am not sure that i've found the answer to my problem. i've got a '68 C10 that someone set-up with working side marker lights. The front driver side marker light won't come on solid with the parking or headlights (the rest do), but the side marker turn signal does work whether or not the headlights/parking lights are on or off. every other light works as it should, including turn signals all around, it's just the one light that won't come on with the headlights or parking lights. i've replaced the bulb and the entire housing/socket. what steps should i take to figure this out? thanks in advance for the assist!

10-11-2016, 06:24 PM	#2
custom10nut Registered User Join Date: Apr 2015 Location: East Tn (In the heart of the Smoky Mtns) Posts: 1,887	Re: side marker lights If your side markers flash at all, somebody tried to retire them to do so. The should only come on steady when your running lights or headlights are on. What do you back ones do when you use you turn signals? I'm curious to see where they found a dual filament bulb that size.

10-11-2016, 06:32 PM	#3
LongBox Registered User Join Date: Sep 2016 Location: Vancouver BC Posts: 784	Re: side marker lights To make the front side marker lights blink with the turn signals, the ground for the marker light goes through the signal light and socket. Someone may have tried to rig this up this way, and someone else on the board may know how to get it to work properly. If it was me, I'd carefully clean up the front parking/turn signal light socket, make sure it is grounded properly, and that the bulb is good. __________________ Rick -69 GMC 910 Long Box, 350 -98 Chev Silverado 1500, 350 Vortec 4L60e -08 Mustang GT Convertible

10-11-2016, 06:32 PM	#4
jescates Registered User Join Date: Aug 2001 Location: Mcloud, Oklahoma Posts: 656	Re: side marker lights Sounds like it's not grounded. If you have a voltmeter, you could remove the bulb, turn on the lights and put the red lead inside the socket and the black lead on the frame and see if you have 12 volts. If you do, then you have lost a ground to that light! __________________ 1970 C-10 LWB 1998 Jeep Wrangled TJ 2009 Honda VTX 1300 2013 Buick Enclave

10-11-2016, 08:01 PM	#5
dmjlambert Senior Member Join Date: Apr 2016 Location: Cypress, TX Posts: 3,859	Re: side marker lights Here is the schematic for 3 different ways of connecting the front side marker, in this post http://67-72chevytrucks.com/vboard/s...=707545&page=2 Use a voltmeter to explore and figure out what voltages you get, and also just examine the wiring to see how it is hooked up and compare to the schematics on that other post. The front parking lamps have 2 filaments. The dim filament is for parking light, and the bright filament is for turn signal. The parking lamp housing must be grounded to complete the connection for either of those filaments inside the bulb. The side marker light uses one filament to do both jobs. There are 2 wires going to it, and no housing ground. Even with the front parking/turn signal completely disconnected or not grounded, the side marker light should still work (it does on my truck). I think it is likely your front driver side marker light is wired for blinker only, and the front passenger side is wired for combo marker and blinker. The combo marker and blinker wiring for the side marker light is not compatible with LED bulbs. As far as I know it must be a regular incandescent 194 bulb. It is possible there are LED bulbs that are not polarity sensitive, so those may work but I have not heard anybody talking about those and I have regular incandescent bulbs.



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