What relay is used for this high idle circuit?

A Radio Shack 275-218 DPDT relay, labeled in the diagram as the Idle control Relay.

How is the brake interlock wired?

A Radio Shack SPDT switch (275-248) is wired between the high idle on/off switched +12V feed and the brake light switch (+12V when pedal pressed), so the relay coil circuit acts as a brake interlock; one switch terminal is not used and the other side goes to ground.

Which TPS and IVS wires are tapped for the high idle mod?

The red/orange wire from the harness to the IVS (relay terminals 5 to 1, with terminal 3 spliced into brown on the IVS), the brown/white wire from the harness to the TPS (terminals 6 to 2), and the grey/white wire on the TPS which connects to the idle speed control potentiometer wiper.

What resistor value is used in the idle speed control circuit?

A 1k ohm resistor is placed between relay terminal 4 and the idle speed control potentiometer.

What vehicle does this diagram apply to?

The diagram is labeled "High Idle on White '95 Diesel."

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1995 Ford Diesel High Idle Wiring Diagram - DPDT Relay, TPS & IVS Mod

Hand-drawn wiring diagram of a diesel high-idle relay circuit

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

AI caption February 2008 · Photo 831 of 1255

This is a hand-drawn wiring diagram titled "High Idle on White '95 Diesel," showing how to add a switchable high-idle circuit to a 1995 Ford diesel. A switched +12V "High Idle on/off" feed passes through a Radio Shack SPDT switch (part 275-248), which is wired as a brake interlock using the brake light switch (+12V when pedal pressed) so the high idle disengages when braking. That circuit energizes a Radio Shack 275-218 DPDT relay (labeled "Idle control Relay") via terminal 7, with terminal 8 grounded. The relay's switched contacts intercept two signal wires: the red/orange wire from the harness to the IVS (terminal 5, normally passed to terminal 1 "Red/orange on IVS," with terminal 3 spliced into brown on IVS) and the brown/white wire from the harness to the TPS (terminal 6 to terminal 2 "Brown/white on TPS splice"). When the relay activates, terminal 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 speed. One switch and one pot terminal are marked "Not used."

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Frequently asked questions

What relay is used for this high idle circuit?: A Radio Shack 275-218 DPDT relay, labeled in the diagram as the Idle control Relay.
How is the brake interlock wired?: A Radio Shack SPDT switch (275-248) is wired between the high idle on/off switched +12V feed and the brake light switch (+12V when pedal pressed), so the relay coil circuit acts as a brake interlock; one switch terminal is not used and the other side goes to ground.
Which TPS and IVS wires are tapped for the high idle mod?: The red/orange wire from the harness to the IVS (relay terminals 5 to 1, with terminal 3 spliced into brown on the IVS), the brown/white wire from the harness to the TPS (terminals 6 to 2), and the grey/white wire on the TPS which connects to the idle speed control potentiometer wiper.
What resistor value is used in the idle speed control circuit?: A 1k ohm resistor is placed between relay terminal 4 and the idle speed control potentiometer.
What vehicle does this diagram apply to?: The diagram is labeled "High Idle on White '95 Diesel."