74 Seatbelt Interlock System
Thread Starter
2nd Gear
Joined: Jul 2024
Posts: 2
Likes: 0
74 Seatbelt Interlock System
Need some help folks. I am about 50% thru a restoration on my 74 with a 350/automatic. Engine is ready to fire up. I have installed the new engine wiring harness and new dash wiring harness with fuse box. Seatbelt interlock relay (mounted to orange connector on passenger side firewall, which I do not have) and seat belt interlock module (typically mounted under one of the seats) have not been wired. Is there any way to start the car without the interlock relay and interlock module installed, using the ignition key? I want to make sure the engine is solid before I move forward completing the interior and installing the forward/rear wiring harnesses. Thanks.
Melting Slicks
Joined: Apr 2021
Posts: 2,670
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From: Minnesota
Thread Starter
2nd Gear
Joined: Jul 2024
Posts: 2
Likes: 0
Thanks for the quick response. Unfortunately, not having the orange block and the i9nterlock relay, that posting does not help me. I have also found that the wiring in the post does not match the colors of the 2024 after-market wire harness. He also doesn't address the removal of the interlock module; he only addresses the interlock relay. Unless I am missing something. 
Race Director
Joined: Oct 2000
Posts: 12,657
Likes: 3,116
From: Shamong, NJ
I don't know if this will be of any help, but when the law was rescinded in 1975, Chevrolet sent this Technical Service Bulletin to dealers explaining how to disable the system.
File Type: pdf
1975 Seatbelt Interlock_TIMJG.pdf
File Type: pdf
1975 Seatbelt Interlock_TIMJG.pdf
Le Mans Master
Joined: Aug 2006
Posts: 7,422
Likes: 1,558
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
