What parts are needed for this high idle circuit?

A RadioShack SPDT switch/relay (part 275-248) used as a brake interlock, a RadioShack DPDT relay (part 275-218) used as the idle control relay, a 1k ohm resistor, and an idle speed control potentiometer.

Which wires are spliced for the high idle mod?

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

How is the brake interlock wired?

The high idle on/off switched +12V and the brake light switch (+12V when pedal pressed) feed the RadioShack 275-248 SPDT brake interlock, with one terminal not used and another going to ground, so pressing the brake cancels the high idle relay.

What does the 1k ohm resistor connect to?

It sits between pin 4 of the DPDT idle control relay and the idle speed control potentiometer, which then ties into the grey/white wire on the TPS.

What vehicle is this diagram for?

It is labeled "High Idle on White '95 Diesel," i.e., a 1995 diesel truck.

Home/ Registry/ Ford/ C-350 (Centurion Conversions)/ “white”/ Photo supermotors.net/registry/media/606227

1995 Ford 7.3 Diesel High Idle Wiring Diagram - DPDT Relay & TPS/IVS Splices

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

‹ ›

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

AI caption February 2008 · Photo 832 of 1255

This is a hand-drawn wiring diagram for adding a manually switched high-idle function to a 1995 Ford diesel (labeled "High Idle on White '95 Diesel"). The circuit uses two RadioShack components: a 275-248 SPDT switch/relay used as a brake interlock, and a 275-218 DPDT relay used as the idle control relay. A switched +12V high-idle on/off feed and the brake light switch (+12V when pedal pressed) feed the brake interlock, which drops out the high idle when the brakes are applied. The DPDT relay's pins are numbered 1–8: pin 7 receives the interlocked +12V, pin 8 goes to ground, pin 5 takes the red/orange wire from the harness to the IVS, pin 3 is spliced into the brown IVS wire, pin 1 goes to the red/orange on the IVS, pin 6 takes the brown/white harness wire to the TPS, pin 2 splices to the brown/white on the TPS, and pin 4 routes through a 1k ohm resistor to an idle speed control potentiometer whose wiper connects to the grey/white TPS wire. A reader can learn the exact splice points, wire colors, relay pinout, and parts needed to build this high-idle modification.

Is this accurate? Sign in to help verify it.

Frequently asked questions

What parts are needed for this high idle circuit?: A RadioShack SPDT switch/relay (part 275-248) used as a brake interlock, a RadioShack DPDT relay (part 275-218) used as the idle control relay, a 1k ohm resistor, and an idle speed control potentiometer.
Which wires are spliced for the high idle mod?: The red/orange wire from the harness to the IVS (relay pins 5, 1, and 3 with the brown IVS wire), the brown/white wire from the harness to the TPS (pins 6 and 2), and the grey/white wire on the TPS, which connects to the idle speed control potentiometer wiper.
How is the brake interlock wired?: The high idle on/off switched +12V and the brake light switch (+12V when pedal pressed) feed the RadioShack 275-248 SPDT brake interlock, with one terminal not used and another going to ground, so pressing the brake cancels the high idle relay.
What does the 1k ohm resistor connect to?: It sits between pin 4 of the DPDT idle control relay and the idle speed control potentiometer, which then ties into the grey/white wire on the TPS.
What vehicle is this diagram for?: It is labeled "High Idle on White '95 Diesel," i.e., a 1995 diesel truck.