Patrick1985

2006 F150 Crew Cab
I installed a led third brake light and now my cruise isn’t working. I know I need to wire in a resistor or 3 resistors(since there are 3 bulbs).... not really sure.... but I could really use someone’s expertise. Basically I need to know 1) do I need a resistor on each bulb? 2) what size resistor? Thanks in advance and if anyone has a picture of this job please share! Thanks again

2008__XL

Only on the third brake light, the center bulb. The other two lights are cargo lights.

ShirBlackspots

This should be good enough: https://www.theretrofitsource.com/mo...-resistor.html Its 40 watts, 7.5 ohms. I currently have a cheap no-name 25W resistor between the brake light wires (Its been there for the last 8 years or so), but I'm going to change it out with the one I linked.

Reminder: These do get very hot, its ok if you leave them inside the space behind the light, but it is possible that they'll warp the light fixture.

Oh, and if you are going to put LEDs in your turn signals, you'll need this: https://www.theretrofitsource.com/pr...elay-ep27.html

650NutKase

I installed the DNA Motoring LED light on mine and did not install a resistor. It's plug and play....

ShirBlackspots

I bet that DNA Motoring LED has a built in resistor, that's why it worked so well for you. But for the rest of us who buy a generic LED bulb, or LED brake light fixture for the third brake light, the no load condition that the GEM sees there, it disables cruise. Someone else said its because the cruise control module thinks you have the brake applied at all times.

2008__XL

There is no GEM module in the 2004-2008 trucks.

ShirBlackspots

Tell that to @Rnlcomp He's a retired Ford master tech.

From this thread https://www.f150forum.com/f2/disable...2017-a-448839/

2008__XL

2004 - 2008 NBS F150 don't have GEMs. They do have "Central Junction Boxes" which is really just the fusebox under the passenger side kickpanel.

Maybe he is referring to something else as the GEM. There are no photos or mentions anywhere about these trucks having a GEM. 97-03 had them.

ProjectSHO89

I'll repeat what 2008__XL said, "There is no GEM module in the 2004-2008 trucks". The referenced statement by another member is incorrect, perhaps he was thinking of the older trucks (97-03)

In any event, the monitoring of the BOO switch is done by the PCM, not an extra module on this generation of truck.

To fix the OP's problem, pick one of the following:
1. Put the incandescent bulb back in.
2. Buy and install an LED fixture or module that includes the circuitry to "pull down" the BOO signal when the pedal is not depressed. Look for a seller's statement that the LED won't disable the cruise.
3. Install a resistor in parallel that will accomplish the same thing.

It doesn't require a high-wattage resistor normally used to suppress hyperflashing (overkill), all you need to do is pull that voltage down so the PCM isn't seeing an open circuit on its input. I don't know what the input impedance of that analog input is, so it would take some experimentation to determine an appropriate resistance. My guess is anything between 1K and 4.7K would likely work.

RLXXI

Interesting, yes I was speaking on an assumption that Ford kept the GEM in lieu of the BCM which is now the norm. I left the dealer 1st qtr 04. When I was researching the next gen 09-14 I saw where the 09-10 had the GEM. I wonder why Ford would change it in favor of a different box then go right back to it for 2 years.

Perhaps it was an experiment that failed thus they went back to it. Who knows. My theory is some bright new engineer wanted to make a name for himself, lol.
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