Turn signal harmonica plug wiring different - 1977 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bigoilman · 11-04-2020, 01:28 PM

In the midst of replacing my turn signal switch and realized that the original has an additional pink/blk and black that the replacement part doesn't have. Looked through my schematics and don't see it there either? What do they operate? Do I need to add them to the new plug? The switch seems to have provisions for them.

Only thing I've found online is for a similar vintage Corvette and those went to the "key alarm" whatever that is. (Edit: found the answer to that, see pic). I guess my truck got that feature (it was a fairly loaded Silverado with Cruise Control) Wires are in positions "E" and "F" on the harmonica connector.

1977 C30 Dually Silverado

**hatzie** · 11-04-2020, 07:31 PM

The 1977 and prior CK pickup harmonica plugs will not mate with the 78 & later cab harnesses.
There were a bunch of wiring changes between 73 & 77. I would download the 1977 wiring diagrams and look through them.

The seatbelt buzzer was used as the headlamps (parking lamps on, ignition key not present, door open) and key in ignition with door open warning as well.

11-04-2020, 01:28 PM	#1
bigoilman Registered User Join Date: Oct 2014 Location: Ocean Springs, MS Posts: 51	Turn signal harmonica plug wiring different - 1977 In the midst of replacing my turn signal switch and realized that the original has an additional pink/blk and black that the replacement part doesn't have. Looked through my schematics and don't see it there either? What do they operate? Do I need to add them to the new plug? The switch seems to have provisions for them. Only thing I've found online is for a similar vintage Corvette and those went to the "key alarm" whatever that is. (Edit: found the answer to that, see pic). I guess my truck got that feature (it was a fairly loaded Silverado with Cruise Control) Wires are in positions "E" and "F" on the harmonica connector. 1977 C30 Dually Silverado Attached Images Last edited by bigoilman; 11-04-2020 at 01:41 PM. Reason: Add pic.

11-04-2020, 07:31 PM	#2
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 4,977	Re: Turn signal harmonica plug wiring different - 1977 The 1977 and prior CK pickup harmonica plugs will not mate with the 78 & later cab harnesses. There were a bunch of wiring changes between 73 & 77. I would download the 1977 wiring diagrams and look through them. The seatbelt buzzer was used as the headlamps (parking lamps on, ignition key not present, door open) and key in ignition with door open warning as well. __________________ 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.



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