Right marker light out?

[87_Rado]

I have been working on my headlights lately and cleaned up the contacts and each plug and used some dielectric grease when reassembling, for some reason my passenger side marker light on the fender will not work. EVERY other light works, headlights, running lights, other marker and blinker are all fine but the passenger side will not light up, however with the truck running when I turn the right blinker on, the marker ligh comes on solid? I'm confused and I've tried searching all over and can't seen to find a post with a similar problem. I cleaned up the battery to firewall and the common lighting ground on the firewall as well. Any help or suggestions would be very helpful this is driving me crazy!

[87_Rado]

Also when I use a test light and connect to the ground on the fire wall, and then probe the socket I have power at the socket with the lights on, but when I put a bulb in nothing happens.. I don't know what else to try

[bd]

Make sure that the front turn bulbs are 1157 or 1157NA and that the locking pins are properly aligned and the bulbs are correctly installed into their sockets.  Also, verify that the front turn bulbs are properly grounded.

[87_Rado]

Bd maybe I should have explained a little better, my running lights are working properly with the proper bulbs, as well as my headlights. I have an 87 with the 2 headlight setup where highs and lows are in the same lamp with running lights underneath, my problem is in the right marker light on the fender, the sockets take 194s I believe, at least thats what was in there previously, and I replaced the bulb with a brand new one and cleaned the socket, I probe it with the test light and I'm getting power to the socket but it's just not lighting the bulb for some reason when I install it. I cleaned both grounds lastnight with no change after I reinstalled them.

[Captkaos]

IF the socket is getting power I would say the bulb was bad.

[bd]

The 194 side marker doesn't "ground" conventionally.  It has two 12-volt feeds to it, depending on circumstances, that can substitute as ground.  One side of the 194 bulb connects to the front 1157 turn lamp filament, the other side of the 194 bulb connects to the front 1157 park lamp filament.  In other words, the 194 bulb illuminates by 'grounding' through one filament of the 1157 bulb while it is 'powered' off the remaining filament of the 1157 bulb. 

Bear in mind there are three wires connected to the front turn/park lamp - 12-volt park (brown), 12-volt turn (blue), and ground (black).  The turn signal circuit works like this: when the turn signal is energized, the turn signal filament (blue wire) of the front turn/park lamp powers up, which simultaneously powers one terminal (blue wire) of the side marker.  The alternate terminal of the side marker (brown wire) connects to the park filament of the front turn/park lamp.  The filament of the 194 bulb has significantly greater electrical resistance than either filament of the 1157 bulb.  So, the 194 bulb essentially connects to the black ground wire of the turn/park lamp, through the park lamp filament, as though that filament is just another conductor.  And, the side marker flashes in unison with the front turn lamp....

The park lamp circuit works like this: the park lamp filament powers up with the running lights (brown wire), which simultaneously powers one side of the 194 bulb (brown wire).  The alternate terminal of the 194 bulb (blue) connects to the turn filament of the front turn/park lamp.  As before, the 194 bulb effectively connects to the black ground wire of the turn/park lamp, through the turn signal filament - and the side marker illuminates continuously.... 

It gets a little more interesting when the turn signal and park lamps are operating at the same time.  In this scenario, the side marker has constant 12 volts on one terminal (brown) and cycling 12 volts on the opposite terminal (blue).  The side marker extinguishes when 12 volts is applied to both of its terminals at the same time, but then illuminates when the front turn lamp cycles off and the side marker grounds (black) through the turn signal filament.  The net result is that the side marker illuminates when the turn lamp extinguishes, and extinguishes when the turn lamp illuminates - so the side marker and turn lamp function 180° out of phase or exactly opposite when both turn and park circuits are energized.

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Occasionally, a single contact bulb is inadvertently substituted for the dual contact 1157, which shorts the double contacts in the base of the bulb socket and the side marker fails to function correctly.  So recheck the right front turn/park lamp.  Use a test lamp clipped to ground to probe the two socket contacts of the side marker lamp.  One terminal should be 12 volts with the park lamps on.  The remaining terminal should be 12 volts with the turn signal flashing.  If this is the case, either the 194 bulb is burned out, or its terminals are not making good electrical connection inside the socket, or a wire is broken inside the socket's pigtail causing an intermittent connection.

[87_Rado]

Bd you were right man thanks alot, after reading what you said about the light being powered through both filaments of the park lamp I checked the 1157 bulb and examined it closely and found out the one filament wasnt making contact, I changed the 1157 in the front right running lamp and the marker light came right on! Something so simple had me so frustrated thanks for the help fellas. However now my righthand blinker is acting up and blinkin very slow lol if it isn't one thing it's another I'm just happy I got all my lights illuminated! Thanks again guys any thought in what the blinker issue may be feel free to chime in

[bd]

If all the lamps are flashing correctly now, replace the turn flasher with a heavy-duty "electronic flasher" available from most auto parts houses (image).

[87_Rado]

Thanks for the help man, sorry for the late reply I'm always busy between work and working on the truck, but your help is much appreciated, I have gotten everything working now and yet another problem popped up, all the lights function as they should accept for the passenger side blinker, it works when there are no lights on, but if I turn on my running lights or head lights the blinker no longer works on the passenger side, the driver functions fine but the passenger just dims out and will not blink, I've cleaned up all my grounds and tried everything I can think, changed the flasher and even tried and LED lasher because I'm using some amazing LED tailights on my flatbed, still no luck! any suggestions would be awesome!

[bd]

Do you have LED turn lamps front and rear?  Is the entire right side affected or just one corner?  Connect a voltmeter between the battery negative post and the ground wire coming from the lamp.  With the right turn signal on, is the meter registering a constant or periodic bump in voltage above zero?

[87_Rado]

Bd thanks for the quick reply that's a great idea I will try that as soon as I get off of work today. I'm teaching myself a bit more and more as I go along about wiring as well as diagnosing problems and I didn't even think about trying this, thanks! I'll be back with results later on today, and to answer your question, yes, the whole right side is affected front and rear, but only when the leadlight switch is engaged, with the headlight swirch off everything works as normal. And no I don't have LEDs all the way around, I only have LEDs on the flatbed in the rear and the stock headlights up front. I used all stock wiring to hook up the leds off the rear tailight harness. I'm gonna try to gather up some pics and see if I can post it here in the member ride or welcome section to give an idea of what my truck is lookin like and where I'm at with it

[87_Rado]

I hooked a voltmeter up today to see what I can come up with this is really bugging me out its the last thing before Iout my truck on the road monday, I hooked black on the voltmeter to the negative cable on the battery and the red probe to the ground coming off the light to the firewall, I got a wierd reading that wasn't constant and would drop low very quickly, I cleaned the ground on the firewall and on the Frame and tried again with the same results, what should I be looking for?

[bd]

...I hooked black on the voltmeter to the negative cable on the battery and the red probe to the ground coming off the light to the firewall, I got a weird reading that wasn't constant and would drop low very quickly, I cleaned the ground on the firewall and on the Frame and tried again with the same results, what should I be looking for?

Provide more detail on, "the ground coming off the light to the firewall" and "I got a weird reading that wasn't constant and would drop low very quickly."  Measuring ground-to-ground should ALWAYS yield zero!  Whether or not an electrical appliance is powered up is immaterial. 

Essentially, the truck has a floating ground that needs to be resolved.  Begin by taking an inventory of all vehicle grounding points.  At bare minimum, you should have battery-to-engine, battery-to-right frame rail, battery-to-radiator support, engine right cylinder head-to-cab sheetmetal, rear lamps-to-bed sheetmetal, bed sheetmetal-to-right frame rail, and various dash appliances including the instrument cluster-to-cab sheetmetal.  If the rear lamps ground to the crossmember, add a jumper between the crossmember and the right frame rail then recheck lamp function.

[87_Rado]

Alright so theres a ground on the passenger side radiator support right above the right side head light, this I where my battery to radiator support ground is, the ground wire coming off the headlight goes up to this location and grounds through a ring connecter which has another wire that also goes down to the right side frame rail, I know I'm having a ground issue that's what I've been thinking I'm just not the greatest at trying to diagnose and pin point it this is my first chevy and got a lot to learn, I appreciate your patience. So now that you have said that I'll try to clear something else up, I checked for battery to radiator support ground, battery to framerail, battery to alternator bracket( sufficient engine ground?) Right cylinder head to firewall, and all the dash grounds go to the bus ground under dash on the parking brake release, however I have made a wooden flat bed on my truck. ALL of the wiring on my truck was hacked from the previous owner so I did a lot of my own wiring in the tailight area. I used the factory "T" after the plug in the rear that splits off and goes to each tailight, I connected the factory wires individually to a set of LED tailights I got from amazon.   The tailights I have hooked up are a three wire set up that have there own ground wire that I just grounded to the bumper and they seemed to work fine accept that one blinker. So now that you mention that I don't think I have my grounds in the rear hooked up correctly. The rear lamp to bed sheet metal ground and bed sheet metal to frame rail ground arent present because there is no bed sheet metal it's all wood, and the lights that are hooked up now are just grounded individually to the rear bumper. So I think a lot of my problem may be coming from this area what would you recommend I do to diagnose this? Take the factory ground wires off the "T" and connect one to the frame rail? Sorry if anything is confusing I can try to clear anything up if you need. Again thank you for your patience I really appreciate the help it's awesome to be able to relate about these problems and get some awesome help

[bd]

Please clarify, "the ground coming off the light to the firewall" and "I got a weird reading that wasn't constant and would drop low very quickly."  Which light?  How many volts is a "weird reading?"  Are you certain the meter was set to "DC Volts" and not "Ohms?"  Were the right turn signals on at the time?  Even more fundamental, have you verified that the right turn signals are actually receiving power from the switch?

Doesn't your flatbed consist of a steel frame to which the bed wood is fastened?  Make sure the steel frame is adequately grounded to chassis.  Connect a temporary jumper wire between the tail lamp ground attachment to the bumper and some shiny bare metal on the right frame rail.  Then connect your voltmeter between a shiny bare spot on the right frame rail and the battery negative terminal.  Does the meter measure any voltage greater than zero at any time with the various lights working?  Do the lights function correctly with the temporary jumper connected?

Now, connect the voltmeter (OR the temporary jumper) between the ground wire that comes directly from the RR lamp and some shiny metal on the right frame rail, bypassing the factory tee splice altogether.  Does the meter indicate any voltage reading greater than zero (OR do the lights work correctly) with the lights on?