D.I.Y.: Ford Diesel Truck High-idle Mod

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2008 Ford F-250 Dually

Upgrade is ideal for Ford truck owners who live in cold climates and spent lots of time idling.

If you daily drive a Ford pickup with a diesel engine, you are likely familiar with a few of the shortcomings of battling a cold winter. On a cold start, the stock idling setup only warms up the engine so much, causing the heating system to perform at less-than-optimal levels. Along the same lines, if you use a diesel truck for work and you spend time with the truck idling in cold climates, such as when loading up before a long haul, you are well aware that the heating system won’t keep the cabin hot at idle.

Fortunately, the High Idle Modification is a fairly simple one, with Ford Truck Enthusiasts forum member “Ryaneverk2” detailing the project for a fellow forum member,  and many others have made use of his information since that initial post. Today, we bring you a look at this simple upgrade that has been written up to function with the optional Ford upfitter switches.

Ford Upfitter Switches

The Introduction

This thread was originally started by “F250SDPowerStroke“, who asked the following question of the community:

“Hey guys, would like to do the high idle mod with my 2006 F-350 using the upfitter switches. I’ve seen a couple of threads about this but they are not real clear to me and don’t mention the 2006. Any help?”

Fortunately, the Stationary Elevated Idle Control (SEIC) system has been built-in to 2005-and-newer Ford Super Duty pickups with a PowerStroke diesel engine, making the modification as simple as some wiring changes.

A Quick Solution

Ryaneverk2 was the first to reply, including links to Ford Fleet materials along with including the following list of items needed. As you can see, he took a humorous approach to this list.

You will need the following:
1ea – 2005 Ford Truck
2ea – red butt connectors (or solder & tape)
1ea – available UpFitter switch (although any 12v switched source will do)
1ea – access to this forum
1ea – crimping tool
1ea – long nose pliers
6″ – stranded hook-up wire (14-16 ga)
11 mm – socket
1ea – ratchet for socket
1ea – ability to follow directions

1ea – garage large enough to enclose the truck (especially when raining)
1 to 6 – 12 oz refreshments
1 – Ford Tough tattoo
1ea – Electrical Engineering Degree
1pr – non-conductive footwear

He then went into detail as to how to connect the SEIC system to the upfitter switches, but rather than quoting the whole process, you can check out his post by clicking here.

2006 Ford F-350

He closed his how-to post with this:

Also, the 2005 are the same as the 2006 models, at least for the SEIC setup. Also, you can use the orange PTO wire, or you can use the purple/light green charge protect circuit wire. That one will vary the idle from 1200-2400 depending on current draw, in order to keep the battery charged properly. Some have noticed that their RPMs will creep up and up all the way to 2400, slowly, even when the current draw is staying steady. The orange wire locks up the torque converter on the tranny, I believe, but stays at 1200. With the orange, you can also wire in a resistor to make the idle stay anywhere from 1200-2400, and it will stay there and not vary, using the resistor. Also, with a manual tranny, the resistor is required.

Using the first link I posted to Q108.pdf, that should give you everything you need to know, and the post I re-posted should sum everything up nicely on how to do it.

Shortly after this how-to information was posted, the OP replied that he had completed the upgrade.

Thanks! This worked like a charm. I can now high idle till my heart’s content. I love this forum!

2015 Ford F-350

V10 Function

The thread goes on for seven pages, with members announcing their love of the simple how-to write up or asking questions about doing the upgrade on other trucks.

05harley250” asked if anyone had performed this modification on a Ford Super Duty with a V10. “Majic31” replied, explaining that he performed the high idle mod on his V10 gas truck with some slight differences.

I did the exact same as listed in this post on my ’07 V10 – solid orange PTO wire to #4 Upfitter Switch wire – it raises the rpm on the V10 from the base 650 to 900.


I haven’t been able to get the variable rpm working using a potentiometer.
Have hooked the Orange/Yellow (PTO_RPM_Select) and the Orange/White (PTO_Engage) but get nothing. Even tried just connecting the two wires directly, without the potentiometer in between – should have got the max (2320 rpm) for a gas engine, but again no effect.

If you are unhappy with the heat levels of the climate control in your 2005-and-newer diesel-powered Ford Super Duty, this thread has the answer to your problem and it is easy enough for anyone to do themselves.

Join the Ford Truck Enthusiasts forums now!

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