This is How to add a MDS light to your dash
This will work for the 2006 - 2008 Dodge Ram as long as you have MDS
The light will come on when the MDS is active (running on 4 cylinders)
What you will need:
- Green LED from Rat Shack 276-271
- soldering iron
- rosin core solder
- drill with 1/4" drill bit
- about 10' of wire 22 ga
- wire stripers
- wire terminal crimpers
- a 1/4" ring terminal for 22 Ga (red)
- Inline wire tap for 22 ga (red)
- pliers to sqeeze splice
- 2" of shrink tube for the 22 ga wire
- 1/4 x 1 and 1/4 bolt and nut
First thing is to find the Brown/Orange strip wire coming from the C3 connector of the PCM located on the fire wall behind the air filter. The top connector is C1 and C4 is the bottom one. The wire bundle from C3 comes over to the fender and up, which gives you good room to pull the BR/OR wire out. Using the wire tap splice in the wire your going to run.
Now run the wire along the top of the engine compartment and I ran it through the existing tie straps that hold the existing bundle.
Then I poked it through the firewall through the grommet that has the hood release cable but you can go through where ever you want.
I used a small plastic plug that is in the drivers side knee booster to mount the light in. I could pop it out with out removing the whole panel. Drill a 1/4 hole in it and you might have to ream it a bit and debur. Mount the led and then side a 1" piece of heat shrink over the wire and then solder the red led lead to the wire. Then solder a short lenght of wire to the black ground lead. Slide another heat shrink tube over that solder connection and shrink with heat, and do the same to the red wire tube. I like to use a portable butane powered soldering iron for this kind of work and as a added bonus, you have a hot exhaust from the iron to shrink the tubing. Now crimp the 1/4' terminal end on the ground wire. The 276-271 LED has a internal resistor to make the install easier. If you hook it up backward you will not hurt a thing, It just will not light up.
Reinstall the plastic panel plug and then go under the dash and attach the ground. I used a 1/4" hole in the large cast aluminum part that supports the steering column and the 1/4" nut and bolt.
You can add a small toggle switch inline to turn off the light. It doesn't matter which wire you put the switch in. Since its mounted so low it doesn't shine in my eye and the steering wheel blocks it for the most part. I have been using it for a few days and here are a few observations - MDS will kick in at a slow speed, accelerating from a stop slowly it will come in at about 10 mph and I could accelerate to highway speed without it dropping out but you better not have anybody on your bumper. At 70 mph it will still kick in but I haven't tried it at any faster speeds yet. It will come on and stay on when you are decelerating or coasting. If you have a heavy head wind it will not come on to often.