Just a disclaimer before I begin. This procedure involves modifying sensitive electronic components - any number of which, if damaged will completely ruin the IDM which can cost anywhere from a couple hundred to over $400. During the process of doing this modification, electrostatic discharge safety procedures must be observed in order to protect static sensitive devices. By following the instructions for this modification, you acknowledge that you have the skill and experience to complete this modification and accept full responsibility for any damage that may result. Please read all the instructions before starting.
It's been widely discussed that raising the output voltage of the IDM will improve performance but the exact effect is not so well documented. In this article, I'll add my personal experience and back it up with dyno proven results.
On the Superduty, the IDM is located on the driver's side, behind the fender liner. There are 4 8MM bolts and 4 7MM bolts holding the liner on. You'll also need to remove the porcupine wire holders from the engine side of the liner to free it to move down, out of the way to access the IDM.
With the liner removed, this is the view back toward the rear of the truck. Here you see the IDM.
Remove the battery cables, then use a 10MM socket to remove the IDM's electrical connector. Once the bolt is loose, release the plastic tab on the side of the connector to free it from the IDM. Next, remove the 2 10MM bolts holding the IDM mounting bracket to the fender.
For the next step, you will need to remove the IDM's cover. You may want to leave the IDM in it's mounting bracket so you can clamp it in a vice for easier handling. This is the most dificult part of the job. The cover is secured by a silicon type substance that maintains a weatherproof seal. It's important to maintain the integrity of this seal when re-installing the cover later in order to continue to insure the protection of the delicate components inside.
There are probably several ways to remove the cover but I chose to carefully drill a 1/8" hole in the corner (holding the box upside down to keep any metal fragments out), screwing in a dent puller and carefully pulling until the corner popped out enough to get hold of and then gently working it the rest of the way off. After completion of the job, I'll seal the hole with a pop rivet and some silicon sealer.
Unfortunately, despite my best efforts, this is how the cover looked when I was done pulling it. Lukily, it's aluminum and it's fairly easy to straighten.
Once inside, this is the component you're looking for - the little blue one with 6042 written on it:
There is some clear gel on the surface of the PC board that may have to be scraped away before the component can be removed. Use a pencil type soldering iron (not a soldering gun, it's too big and too hot for the small conponents) and some forceps, tweezers or other slender needle nose pliers to gently heat and remove the resistor.
For the replacement resistor, I placed an order with Digi-Key corporation. The resistor is a .5W 73.2Kohm 1% metal film. My IDM is an IDM 120. IDM 100 and 110 require a 75Kohm.
Here's a shot of the packages I received. I ordered both resistor values just to be sure I had the correct one.
Here's a shot of the components just to give you an idea of the scale.
Next, bend the leads on the new resistor and snip them off short. Attach the part as ahown here using a small quantity of high quality, low lead solder. The milky appearance on the board is the result of the heat in close proximity to the gel sealant.
Once the new resistor is installed, re-connect the IDM to the trucks harness, re-attach the battery cables and start the truck to test the operation.
Here's the IDM re-installed for testing:
After a successful test, use some appropriate sealant ((Ford) F5TZ-19G204-AB (5oz, 1/2 caulk tube), (Wacker) T-442 or (International) 1830858C1 is recommended) and replace the IDM cover. I took the extra step of clamping the IDM between blocks of wood for 24 hours to ensure that the sealant was completely cured.
Finally re-install the components in their proper locations, replace the fender liner and re-attach the wiring harness holders.
Dyno results and driving impressions will be added at a later time. Please post any additions or corrections and I'll incorporate them into the article.