1975 Dash Wiring Harness Manual Trans w/o Interlock Seat Belts
1975 Corvette Dash Wiring Harness for Manual Transmission without Interlock Seat Belts. Application is for Coupes and Convertibles, small block, big block, manual transmission and without interlock seat belts.
WHAT IS THE SEATBELT / STARTER INTERLOCK SYSTEM?
This system prevents a vehicle from starting unless the seat belts are fastened. But it goes beyond that. The seat belts must be fastened within a specific sequence. For example, the driver (and front seat passenger) must get into the car, close the door(s), sit down, and then fasten the seat belts. If the seat belts are not fastened, or if they are fastened in an incorrect order, the car will not start. All 1974, and early-to-mid 1975 vehicles had the seatbelt interlock system.
HOW DO I IDENTIFY IF MY VEHICLE HAS/HAD THIS SYSTEM?
All 1974 vehicles had the seatbelt/starter interlock system. As for 1975 vehicles, unless you are the original owner or know the history of the vehicle, unknowing wiring modifications by previous owners or repair shops can make this identification difficult. We suggest trying to locate the specific components of the interlock system within the vehicle.
• Logic Module and Sensors often located behind or under the seats. (in Corvettes, it's located behind the seats)
• Starter Interlock Relay mounted in console or under the dash. (in Corvettes, it's mounted in the console)
• Manual Starter Bypass mounted on firewall or on the fender well. (in Corvettes, it's mounted on the firewall)
• According to an early 1975 Technical Service Bulletin (TSB) issued by Chevrolet (and probably pertaining to all GM passenger cars) "A new non-sequential 4 to 8 second delay seat belt system will be installed on all 1975 Chevrolet passenger cars built after February 24, 1975. The new system will have an instrument panel warning light that will illuminate every time the ignition switch is turned on whether or not the driver's seat belt is buckled, but will automatically go off after 4-8 seconds. The buzzer will also be controlled by a 4-8 second timer, but will operate only if the driver has not buckled up prior to turning on the ignition. If no attempt is made to buckle up after turning on the ignition, the buzzer will also shut off after 4-8 seconds."
WHAT DOES THIS ALL MEAN?
According to the TSB information above, Chevrolet is stating that no cars built after February 24, 1975 had the seatbelt interlock system. However, we recommend that you verify all of the information provided above.
CAN I BYPASS OR DISABLE THIS SYSTEM?
From our experience, there is no documentation published on how to do so (most likely due to liability reasons). We can not offer any assistance in this area.
CAN I REPAIR THIS SYSTEM?
Repair of the seat belt interlock components is limited to their replacement. Testing the system requires the use of a special tester, which connects to the seat belt/starter interlock system at several points. About the only place that you are likely to find this tester, if you're lucky, is at your local dealer.
CAN I ELIMINATE THIS SYSTEM?
If you have a 1975 GM model vehicle, it is possible. However, because the interlock system was integrated into several wiring harnesses, you will usually need to replace the Dash, Engine and Rear Body Harnesses with harnesses made for "WITHOUT seatbelt interlock system".
NOTE: If you've made the decision to completely rewire your 1975 vehicle, we strongly recommend that you purchase your wiring configured for "WITHOUT seat belt interlock system". Doing so will allow you to eliminate all of the electrical components that are part of the seat belt / starter interlock system; components that may eventually fail, are no longer made, and are hard to find.
CAN I FIND REPLACEMENT PARTS FOR THE INTERLOCK SYSTEM?
We offer wiring harnesses for 1975 GM vehicles with or without the interlock system. However, the other components of the system (logic module, sensors, bypass device, and relays) have long been discontinued and are difficult to find. We do not know where to obtain these components but suggest a junk yard, swap meet, ebay, or a car club member.
Our Original Design Series™ wiring harnesses are manufactured exactly as the wiring was made when your vehicle left the factory in St. Louis. These harnesses are made to the exact O.E.M. (original equipment manufacturer) specifications, using the original factory blueprints, and are factory-correct in every way. These are full-assembled, ready to install, “plug & play” accurate reproduction wiring harnesses. You will NOT have to cut any wires, crimp any terminals, or make any modifications to these harnesses when installing them in your 1975 Corvette.
A commonly asked question and a much needed answer is "What does this harness" connect to?
1975 Corvette Dash Wiring Harness for Manual Transmission without Interlock Seat Belts connects to:
- Air Conditioning & Heater Control Light
- Ammeter
- Brake Light Switch
- Brake Warning Light
- Bulkhead Connector (passes through firewall)
- Cigarette Lighter
- Cigarette Lighter Light
- Clock
- Console Ground
- Courtesy Light (driver and passenger side)
- Courtesy Light Switch (driver and passenger side)
- Door Ajar Warning Light
- Fuel Gauge
- Fuse Block
- Ground (to hinge pillar inner reinforcement)
- Hazard Flasher
- Headlight Dimmer Switch
- Headlight Door Warning Light
- Headlight Switch
- Heater or A/C Harness Connection
- Hi-Beam Light
- Hood Scoop Air Door & Transmission Kick-Down Switch (at gas pedal)
- Horn Relay
- Ignition Key Warning Buzzer
- Ignition Switch
- Instrument Cluster Ground (left & right side)
- Instrument Light
- Neutral Safety Switch Extension Harness Connection
- Oil Pressure Gauge
- Parking Brake Warning Light Switch
- Radio
- Radio Capacitor Connection
- Rear Body Harness Connection
- Seat Belt Buckle Connection (driver side)
- Seat Belt Warning Buzzer
- Seat Belt Warning Light
- Seat Belt Warning Timer
- Tachometer
- Temperature Gauge
- Turn Signal Flasher
- Turn Signal Light (left & right side)
- Turn Signal Switch Connection
- Windshield Wiper & Washer Switch Light
- Windshield Wiper & Washer Switch
Also known under these part numbers: (For reference only)