Just wondering if anyone know if you can hook your gauges up so when you dim your dash your gauges dim as ? and I've got cobalt gauges,

im pretty sure for the illumination power you dont just use a 12V line, you splice into the power for say the traction control button or the cigarette lighter globe socket as that's a power source which drops with the dash light dimming.

Even though that will dim the lighting, it will still be brighter than the dash lighting, so you can to install a variable Pot which lets you turn a little screw and it will drop the brightness level (depending on how much you turn it).

Someone please correct me if im wrong

Does any one know what wire to splice on the traction control button ?

I too have recently had cobalt gauges installed, and have been puzzling over the dimming problem.

In short, it seems Ford has a rather weird way of dimming dash lights. At least I assume all the dash lights dim the same, I've only been focussing on the bulb socket behind the cigarette lighter.

Having read the PDF manuals & confirming with a multimeter, the following applies:

The lights are not dimmed by varying the positive voltage fed to them, but by raising the earth potential on the negative side using Pulse Width Modulation. This means that when the dash lights are at their dimmest, the "Earth" wire is actually reading +8.45V, with respect to earth.

As a result, a normal bulb would be dim, since it has +12V on one side, and +8.45V on the other, hence the bulb only has 3.55V across it, which = dim.

When the dash lights are brightest, the "Earth" wire reads +0.265V, creating almost 12V potential difference across the bulb, which = bright. Naturally the other two dimmer settings are in between these - you get the idea.

This doesn't help us though, since we only get one wire to feed a positive voltage into the gauges, the other side of which is grounded, as you'd expect.

So if you hook up the +12V wire from your cigarette lighter to the gauge illumination input, it doesn't dim at all. If you hook up the "Earth" wire, the gauges dim, but opposite to the dash lights. Bugger.

So, I'm in the process of building a simple transistor circuit to get the dimming happening how it should. So far it looks like using 4 components (NPN Transistor + 3 resistors) and costs less than $5 to build, providing you have some wire & solder kicking around somewhere.

I should point out that I haven't actually built or tested it yet, that's a job for tomorrow. But it works, in theory. I hope.

As for the traction control button illumination, I'm pretty sure I checked it & it was the same as the cig. lighter bulb. However I plan on getting my +12V when-the-lights-are-on supply from there, since the cig lighter bulb does other weird stuff like come on with the interior lights when you unlock, and stays on for a minute or so (or until you lock) after shutting down the engine. Use the cig. lighter bulb wire for cool factor if you like night-lights.

Watch this space....

tapped to the cigarette lighter harness is a small plug with two wires attached. take your dimming signal from those. I found that to be the easiest

81CJH if what your saying is true then how has everyone else been using the signal from the traction control switch or the ciggy lighter bulb in the past to successfully dim their gauges?

Let us know how the circuit you make up works. maybe you could put a variable pot in there too so you can adjust the overall signal at the start of your circuit as ive been told the brightness of the cobalt gauges are brighter than the dash gauges.

Taking power from the ciggie light worked for me, putting a rheostat (variable resistor) in series to dim the lights. I have notice that if I try to dim it to much the boost gauge light dims quicker than the other two, it might have a different value LED in it but I am not sure.

Taking power from the ciggie light worked for me, putting a rheostat (variable resistor) in series to dim the lights. I have notice that if I try to dim it to much the boost gauge light dims quicker than the other two, it might have a different value LED in it but I am not sure.

Can I ask how you hooked up your rheostat? Which wires where etc.

I'm still hanging on to a glimmer of hope that I've missed something really obvious.

Sorry about the crap pics, the GF's camera battery has died so I am reduced to using the camera phone.

As you can see the Black/Ground is connedted to the blue/red wire of the Cig Lite and the Red is connected to the Blue/white.

I ran the red wire to the traction control hole so I could access the POT/Rheostat when I removed the Trac Control Button.

Edited September 22, 200719 yr by seventytwo

Can I ask where did you get the POT/Rheostat from and what's it rating ?