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.
Distributor Modulator: Description
The electronic distributor modulator system controls emissions by eliminating vacuum advance below 23 miles per hour on acceleration, and below 18 miles per hour on deceleration. It is used on Econoline window vans, and F-100 2-wheel drive trucks. The four major components of this system are the speed sensor, the thermal switch, the electronic control module, and the distributor vacuum control valve, also known as a ported vacuum switch (PVS). The thermal switch is located in the right or left door pillar, the speed sensor is in line with the speedometer cable, and the control module is mounted under the dash panel. The ported vacuum switch is threaded into the coolant outlet elbow.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.