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Okay so I am getting ready to install exhaust brake switch. I want to connect it so that it turns on tow haul also. 1 switch turns it all on. So I have dpdt rocker switch. What I am lacking is info on tow haul activation. I have looked an not quite found what I am looking for. Is the tow haul activated by a momentary button? Or does it latch some where else in the program/bcm. If I connect a button in parallel so it is on all the time will cause a problem. Also switch i have has led light w/ 100ohm in line. Will that cause an issue in series with this? I could do it with a relay also but if the coil of the relay is in series with exhaust brake wires will that cause a problem? I have heard an led will what about a coil from a relay?
 

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Is the exhaust brake switch for activating the factory turbo brake? If so, that has an alternate shift schedule for the transmission as well that will be activated when you turn on the exhaust brake. The Tow/Haul switch is a momentary switch to the BCM and would need a non-continuous circuit (DPDT wouldn't work for that). The exhaust brake shift calibration is decent and keeping it separate gives you three calibrations to chose from while driving.

I believe one of the prior write-ups on the factory exhaust brake mentioned a problem with led switches, but I am not certain. Using the switch to activate the relay is the better route.
 

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I'm curious as to whether you ever sorted this out? I'm not quite as concerned about the TH switch...but I'd really like to install a proper ON/OFF switch on the exhaust brake. I activate the exhaust brake every time I start the truck and it would be so much easier if I could just have a rocker switch that I could leave in the ON position all the time, but still be able to turn it off if needed.
Does anybody know the wiring schematic or even just the color of the wires in the loom behind the switch block?
Mine is a 2012 LML 2500HD and there are 4 switches along the bottom of the center console (brake pedal height adjust...traction control etc...rear proximity sensor OFF...and the exhaust brake.
I was wondering, if I knew what the two (?) wire colors are for the exhaust brake switch, I may be able to just splice-in 2 extra wires to a simple SPST switch and leave the factory wiring as it already is.
Regards from Australia,
Roachie
 
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