Need Light Placement Input

nubuilder

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Perfect!!!
Thanks for all the help Bernie!

One more question though.
All my parking lights flash as a turn signal too and there are only 2 wires going to each bulb (power & ground).
Should I just go back to the headlight knob and get the signal from there since my switch in the cab is right next to it anyways? - I don't see a problem with that and it would be really convinient. - I'm pretty sure the previous owner used the headlight lead from the knob to activate his driving lights that he took off since there is one of those crimp-on things that splices into the wire.
 
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Bernie

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Perfect!!!
Thanks for all the help Bernie!

One more question though.
All my parking lights flash as a turn signal too and there are only 2 wires going to each bulb (power & ground).
Should I just go back to the headlight knob and get the signal from there since my switch in the cab is right next to it anyways? - I don't see a problem with that and it would be really convinient. - I'm pretty sure the previous owner used the headlight lead from the knob to activate his driving lights that he took off since there is one of those crimp-on things that splices into the wire.

It might seem like the parking lamps are flashing, but it's a dual filament bulb, and works just like your brake lights and signals in the back. One filament is for the park lights, the other is for the (brighter) signals. The two wires are both "hots", one for the park filament, one for the signal filament, with the ground being supplied through the bulb socket body itself. Pop a bulb out and take a good look at it and you'll see what I mean.

You can tap into the park light circuit anywhere it's convenient for you, and inside the dash is as good a place as any, and a little better than under the hood because it's then not subject to any water spray.
 
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Bernie

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BTW, the dual filaments are why you can have a brake light out but still have park lamps, or why a park lamp might be out but the signals still work - only one of the filaments has burned out in that case. :)
 

nubuilder

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Perfect!!!
Thanks for all the help Bernie!

One more question though.
All my parking lights flash as a turn signal too and there are only 2 wires going to each bulb (power & ground).
Should I just go back to the headlight knob and get the signal from there since my switch in the cab is right next to it anyways? - I don't see a problem with that and it would be really convinient. - I'm pretty sure the previous owner used the headlight lead from the knob to activate his driving lights that he took off since there is one of those crimp-on things that splices into the wire.

It might seem like the parking lamps are flashing, but it's a dual filament bulb, and works just like your brake lights and signals in the back. One filament is for the park lights, the other is for the (brighter) signals. The two wires are both "hots", one for the park filament, one for the signal filament, with the ground being supplied through the bulb socket body itself. Pop a bulb out and take a good look at it and you'll see what I mean.

You can tap into the park light circuit anywhere it's convenient for you, and inside the dash is as good a place as any, and a little better than under the hood because it's then not subject to any water spray.
Now I really feel stupid. I've noticed that happen before. For instance when one bulb is loose, it will light up fine with the parking lights and not with the blinker. - Glad to finally know that.

I think I'll just go with the under dash location since it would be a lot less wiring and be protected better.

Thanks again Bernie :applause:.
Now I can't wait to get started on this now that I know what to do.


For anyone wondering, I'll start a new thread on the install and wiring of my LED lights and HIDs.
 
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Bernie

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Yeah, it's surprising how many folks don't realize that there's two filaments in those bulbs. Of course, that only applies to vehicles without completely separate signals. When you have separate signals and park lamps then they use single filament bulbs.

Interesting side note, in NYC if you have a broken dual filament bulb, not just one filament burned out but really broken, especially if it's a tail light, and get stopped for it, the nice LEO can, and often will, write you not just one but three fines. One for inop signals, one for inop marker lights, and one for inop brake lights. At (back in the 90's) $55 each. And if it's on the left side of a trailer they can add a fourth ticket for inop license plate illumination, since the left parking light on most small trailers usually also illuminates the plate through a small clear window in the bottom of the housing.

Fortunately, in such a case, if you have the bulb replaced and get a state inspector to sign off on it (which most will do if their shop replaces the bulb - might cost you $15-20 though) you can then get all the fines dismissed pretty easy. Most of the time you just go to the station house where the ticket was issued (within 14 days) and show the desk officer the receipt for the repair with the inspection stamp on it and he'll void the tickets.

I've seen a lot of NYC cops do this (multiple tickets for the same bulb) when the driver is being a total asshat. Most of the time, if you're polite and explain you didn't know about it, you'll get off with just a warning. But heaven help you if that same officer sees you with that same broken light a few days later, because then you will get every ticket he can write, and probably one or two more after he looks over the vehicle a little closer. And those will generally not be dismissed of voided.
 

nubuilder

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Wow, 4 tickets for 1 bulb :eek:!

Here's one thing I never understood about my truck's tail lights. There are 2 blubs, both of which are dual fillament. Only the bottom one flashes with the signal and comes on with the brakes. The top one is just there as sort of a marker light. It doesn't even come on with the brakes. I really wish the top one would be the blinker and the bottm be the brake, but I can't rewire it because of the stupid circuit board that is used. I really wish they would have been seperate sockets for each bulb. Damn engineers at GM :fume:.
 
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Bernie

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Wow, 4 tickets for 1 bulb :eek:!

Here's one thing I never understood about my truck's tail lights. There are 2 blubs, both of which are dual fillament. Only the bottom one flashes with the signal and comes on with the brakes. The top one is just there as sort of a marker light. It doesn't even come on with the brakes. I really wish the top one would be the blinker and the bottm be the brake, but I can't rewire it because of the stupid circuit board that is used. I really wish they would have been seperate sockets for each bulb. Damn engineers at GM :fume:.

Well, look at it this way, you can always use the top one as a spare if one of the brake lights goes out. Just swap it with the brake light that's out and you'll still have it working as a marker and the brake light will then work too. :)

Oh, and another possibility... Check and see which one comes on when you use your 4-way flashers. They may have hooked those up to the top bulbs, so that you still retain brake lights when using the 4-ways.

I'd check on my truck, but mine has a utility back, so the lights are completely different.
 

nubuilder

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Well, look at it this way, you can always use the top one as a spare if one of the brake lights goes out. Just swap it with the brake light that's out and you'll still have it working as a marker and the brake light will then work too. :)

Oh, and another possibility... Check and see which one comes on when you use your 4-way flashers. They may have hooked those up to the top bulbs, so that you still retain brake lights when using the 4-ways.

I'd check on my truck, but mine has a utility back, so the lights are completely different.
That is a good point.

I have tried that. When you put the flashers on, the bottom bulbs blink just like the signals, but when you put the brakes on all the lights stop flashing and light up the bright filament (even on the front parking lights). Very stupid design since when you even touch the brake pedal, you defeat the purpose of hazards.

Once again, back to the stupid circuit boards :fume:.


On another side note:
Do I need to make a harness like this? - Look at the diagram below the image.
I don't really understand the point of this though. Some guys have said that the newer GMT400's need a relay harness whereas the older ones don't. I'm not sure what happens so you know you need one, but I'm sure I'll find out when I try to use them without a relay harness.
 
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Bernie

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On another side note:
Do I need to make a harness like this? - Look at the diagram below the image.
I don't really understand the point of this though. Some guys have said that the newer GMT400's need a relay harness whereas the older ones don't. I'm not sure what happens so you know you need one, but I'm sure I'll find out when I try to use them without a relay harness.

Is the question "Do I need this for my HIDs" or is it "Do I need it for the LEDs?"

For HIDs, yes, for LEDs, no.

GM trucks, up until '01 or '02 (maybe even beyond) used undersized wire for the headlamp feeds, which means the bulbs get less voltage than they actually should. To correct this a few places sell (or you can make it yourself) a wiring harness that uses a relay to control the headlamps, and feeds them directly from the battery with proper sized wiring. It plugs right into the existing harness and uses the power that would normally be illuminating the headlamps to just energize the relays (one for each bulb), which then feeds them power direct from the battery. HIDs can be very sensitive to voltages, and if the voltage is too low may not even illuminate.
 

nubuilder

Why buy new when you can restore?
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On another side note:
Do I need to make a harness like this? - Look at the diagram below the image.
I don't really understand the point of this though. Some guys have said that the newer GMT400's need a relay harness whereas the older ones don't. I'm not sure what happens so you know you need one, but I'm sure I'll find out when I try to use them without a relay harness.

Is the question "Do I need this for my HIDs" or is it "Do I need it for the LEDs?"

For HIDs, yes, for LEDs, no.

GM trucks, up until '01 or '02 (maybe even beyond) used undersized wire for the headlamp feeds, which means the bulbs get less voltage than they actually should. To correct this a few places sell (or you can make it yourself) a wiring harness that uses a relay to control the headlamps, and feeds them directly from the battery with proper sized wiring. It plugs right into the existing harness and uses the power that would normally be illuminating the headlamps to just energize the relays (one for each bulb), which then feeds them power direct from the battery. HIDs can be very sensitive to voltages, and if the voltage is too low may not even illuminate.
OK so I guess I'll need to use a relay then.
Can I buy a factory end that is on the wiring harness of the vehicle (male end; 2 prong) at my local parts store so I can still make my harness plug-and-play?
 

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