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**hatzie** · 11-13-2023, 08:13 PM

You'll loose one of the neat things that GM did with the side marker lamps when you change the front 1157A and the front side marker 168 T10 base peanut bulbs to an LED bulb.

Rather than wrap the parking/turnsignal lamp housing around onto the fender GM electrical engineers did something fairly clever.

The side marker lamps don't have a ground. They're tied to the Parking lamp and Turnsignal hot wires. LED bulbs will not work in the front sidemarker T10 peanut bulb sockets.
-At night properly working side markers will go dark when the turnsignal lamp lights and light up when the turnsignal goes dark.
-During the day the side marker lamp will light up synced with the turnsignal on each side.

You can get away with decent LED bulbs in the tails but you'll want to find bulbs that are designed to use the reflector dish in the taillamp.
1156, 1157, and 168 Sylvania ZEVO bulbs are designed to work properly with the filament bulb reflectors and you can get em at O'Riley.

11-13-2023, 08:13 PM	#6
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 4,916	Re: LED front turn signals You'll loose one of the neat things that GM did with the side marker lamps when you change the front 1157A and the front side marker 168 T10 base peanut bulbs to an LED bulb. Rather than wrap the parking/turnsignal lamp housing around onto the fender GM electrical engineers did something fairly clever. The side marker lamps don't have a ground. They're tied to the Parking lamp and Turnsignal hot wires. LED bulbs will not work in the front sidemarker T10 peanut bulb sockets. -At night properly working side markers will go dark when the turnsignal lamp lights and light up when the turnsignal goes dark. -During the day the side marker lamp will light up synced with the turnsignal on each side. You can get away with decent LED bulbs in the tails but you'll want to find bulbs that are designed to use the reflector dish in the taillamp. 1156, 1157, and 168 Sylvania ZEVO bulbs are designed to work properly with the filament bulb reflectors and you can get em at O'Riley. __________________ 1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials... 1973-1991 GM Light Truck Service, Unit/Overhaul, Wiring Manuals, Parts Books and Some 1968-1999 GM Service Training textbooks in PDF 1988-1998 GMT400 CK service manual project 1988-1993 GMT400 CK parts books. 1967-1972 GM Light, Medium, & Heavy Truck Service Manuals in PDF Please include at least the year and model in your threads. It'll be easier to answer your questions. And please let us know if and how your repairs were successful. Last edited by hatzie; 11-13-2023 at 08:21 PM.