Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
4 In. Hg Vacuum Switch
This switch is mounted on a bracket attached to center of firewall (Natural color). The switch is controlled by carburetor ported vacuum and has a normally open electrical switch when vacuum level is below 4 in. Hg. When vacuum level exceeds 4 in. Hg, the electrical switch closes. This indicates to MCU that either a closed or wide open throttle condition exists.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.