Front parking/marker light issue

[mran613]

Hi,

I am having an issue with my front parking lights on my 1987 V20 pickup and I really can't afford to have a mechanic search for it. My front right parking light/marker lights are having issues. There are a couple issues and I only have a test light.

Please refer to the attached diagram for the following questions.

First general question: when the parking lights are on should power be going to both power sides of the sockets? For instance, on the left side should power be going to both the lt blue and brown wires?

I am asking because that is the case on the left side however the blue wire doesn't have power on the right side when the parking lights are on. Also, the brown wire lights up my test light but barely has enough to glow the element in the bulb.

If the blue wire on the right side should have power with the running lights on, I take it the 2 causes would be a broken wire or bad headlight switch?

Thank you for any help you can give me.

Mark

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[Curt]

First thing I would look for is a bad ground.Then I would check the headlight switch if none of the wiring is loose or broken,frayed.

 

[SirRobyn0]

Ok I hope this will help. When the running lights are turned on or the headlights are on the the brown wire should get 12 volts and your test light should be good and bright. All voltages are 12 volts and should light up your test light good, the reason the running lights are dimmer is because of the filament in the bulb is a lower wattage. Please make sure you have a good ground. Bad grounds can cause all kinds of oddities. Next I'd take a good look at the sockets. The thing is front and rear running lights and turn signals come from the same source, so if you have an electrical oddity in the front I would think it would be likely you'd have it in the back. If not I'd really hone in on grounds first, sockets second then headlight switch.

 

[Turbo4whl]

Mark, If you are testing the left side socket with the bulb removed, then yes there will be power to both wires. It gets to the blue wire from the side marker bulb. Remove the side marker bulb and you will only have power on the brown wire.

The side markers do not have a dedicated ground. Fed with both the parking lamp circuit and the turn lamp wire. It lights when the parks are on because it grounds through the turn lamp. So if the parking lights are on it blinks off with the turn signal on. If the parks are off, it blinks on with the turn.

Left is fine. Your right side has a poor connection somewhere. Head light switch is fine.