What parts are needed for this high idle modification?

The diagram calls for a RadioShack SPDT device (part 275-248), a RadioShack DPDT relay (part 275-218), a 1k ohm resistor, and an idle speed control potentiometer.

Which TPS and IVS wires are tapped for this high idle circuit?

The red/orange wire from the harness to the IVS, the brown wire on the IVS, the brown/white wire from the harness to the TPS (spliced at brown/white on TPS), and the grey/white wire on the TPS which connects to the idle speed control potentiometer.

How is the idle speed adjusted in this circuit?

Relay pin 4 feeds through a 1k ohm resistor into an idle speed control potentiometer, whose output goes to the grey/white wire on the TPS, allowing the high idle speed to be adjusted.

What vehicle is this diagram for?

The diagram is labeled "High Idle on White '95 Diesel," indicating a 1995 diesel vehicle.

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1995 Ford Diesel High Idle Wiring Diagram - DIY Relay Mod (TPS/IVS)

Hand-drawn wiring diagram of a high-idle relay circuit with resistor

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Hand-drawn wiring diagram showing a RadioShack DPDT relay, brake interlock, TPS feed and 1k-ohm resistor for a diesel high-idle control.

AI caption February 2008 · Photo 829 of 1255

This is a hand-drawn wiring diagram for adding a high-idle control circuit to a 1995 diesel (labeled "High Idle on White '95 Diesel"). The circuit uses two RadioShack components: a SPDT switch/relay (part 275-248) used as a brake interlock, and a DPDT relay (part 275-218) used as the idle control relay. A switched +12V "High Idle on/off" feed passes through the brake-interlock relay, which is controlled by the brake light switch (+12V when the pedal is pressed), so pressing the brake disables the high idle. The DPDT relay's pins are numbered 1–8: pin 7 receives the switched power, pin 8 goes to ground, pin 5 takes the red/orange wire from the harness to the IVS (idle validation switch), pin 6 takes the brown/white wire from the harness to the TPS, pin 3 is spliced into the brown wire on the IVS, pin 1 connects to red/orange on the IVS, and pin 2 splices to brown/white on the TPS. Pin 4 routes through a 1k ohm resistor to an "Idle speed control" potentiometer, whose wiper connects to the grey/white wire on the TPS, allowing adjustable high-idle RPM. One switch terminal and one pot terminal are marked "Not used."

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Frequently asked questions

What parts are needed for this high idle modification?: The diagram calls for a RadioShack SPDT device (part 275-248), a RadioShack DPDT relay (part 275-218), a 1k ohm resistor, and an idle speed control potentiometer.
How does the brake interlock work in this circuit?: The switched +12V high idle feed passes through a brake interlock relay controlled by the brake light switch (+12V when the pedal is pressed), so the high idle circuit is interrupted when the brake pedal is pressed.
Which TPS and IVS wires are tapped for this high idle circuit?: The red/orange wire from the harness to the IVS, the brown wire on the IVS, the brown/white wire from the harness to the TPS (spliced at brown/white on TPS), and the grey/white wire on the TPS which connects to the idle speed control potentiometer.
How is the idle speed adjusted in this circuit?: Relay pin 4 feeds through a 1k ohm resistor into an idle speed control potentiometer, whose output goes to the grey/white wire on the TPS, allowing the high idle speed to be adjusted.
What vehicle is this diagram for?: The diagram is labeled "High Idle on White '95 Diesel," indicating a 1995 diesel vehicle.