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03 Silverado Tails On A 99 Sierra?

Jim GMC

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Jim GMC Enthusiast

Jim GMC

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I just bought a set of 2003 Silverado tails and the top light doesn't fit in the taillight lens. One of the brackets is too big to fit in the lens. Anyone else have this problem? Also, it looks like there are 4 places to put bulbs in and in the 99 Sierra there are only 3 bulbs, what is the 4th one for? Its at the very bottom and is smaller then the rest. Is it just a taillight?

Jim GMC Enthusiast

Jim GMC

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I now realize I need a new harness (from what I searched, I should have searched first...sorry). But noone said what harness they got or where they got it from. Does the harness allow for the 4th bulb?

c4cruiser Enthusiast

c4cruiser

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"Upgrading" the rear lamp assemblies was something I was going to do to my old 99 Silverado (it had the amber turn signals) when the newer all red lamps came out, asI thought they would look better. After seeing some on newer trucks, I decided that the light output of the red tun signal on the new style lens was not as visible as the old style yellow lamp especially at night. So I never did the upgrade.

 

As to the 4th bulb and harness, yes, you do need the harness to get that 4th bulb to work as it was designed. That 4th bulb is the side marker light and the harness allows it to flash opposite the turn signal bulb when the headlamps/tail lamps are off in the same way the front side marker light works. IIRC, there was a forum vendor that sold the new-style lamps and the GM harness as a set. The harness is most likely still available from GM.

 

You could simply tap into the tail lamp wire for powering up the side marker lamps if you don't want to mess with the additional harness.

Jim GMC Enthusiast

Jim GMC

Posted
  • Author
Posted
"Upgrading" the rear lamp assemblies was something I was going to do to my old 99 Silverado (it had the amber turn signals) when the newer all red lamps came out, asI thought they would look better. After seeing some on newer trucks, I decided that the light output of the red tun signal on the new style lens was not as visible as the old style yellow lamp especially at night. So I never did the upgrade.

 

As to the 4th bulb and harness, yes, you do need the harness to get that 4th bulb to work as it was designed. That 4th bulb is the side marker light and the harness allows it to flash opposite the turn signal bulb when the headlamps/tail lamps are off in the same way the front side marker light works. IIRC, there was a forum vendor that sold the new-style lamps and the GM harness as a set. The harness is most likely still available from GM.

 

You could simply tap into the tail lamp wire for powering up the side marker lamps if you don't want to mess with the additional harness.

 

 

Thanks for the info. I am gonna go back to the junkyard where I got the lights and see if I can get the harness' from the truck the lights came off of. They just took them off when I wanted them, the harness' should (hopefully) be cheap.

lsorah0001 Enthusiast

lsorah0001

Posted
Posted

There is a way to add the 4th light without the entire harness. You only need two 194 sockets (few bucks at local autoparts store) They will work just like factory. I'll look to see if i can find the diagram.

Edit: You tap the positive wire of the "4th bulb" into the positive of parking light and the negative of the "4th light" into the positive of the turn signal. This way, it comes on with the parking light, loses ground when the turn signal is on effectively turning it off. This creates the factory wig-wag.

Jim GMC Enthusiast

Jim GMC

Posted
  • Author
Posted
There is a way to add the 4th light without the entire harness. You only need two 194 sockets (few bucks at local autoparts store) They will work just like factory. I'll look to see if i can find the diagram.

Edit: You tap the positive wire of the "4th bulb" into the positive of parking light and the negative of the "4th light" into the positive of the turn signal. This way, it comes on with the parking light, loses ground when the turn signal is on effectively turning it off. This creates the factory wig-wag.

 

 

Thanks for the info. I ended up getting the harness from the truck at the junkyard that I got the lights from. They were $20 each and plugged right in and everything works right.

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