I've tried to switch the lights out in my heater control panel to 3 mm LED lights but they don't light once connected. I have soldered them in, tried it with the key off and also with the truck started and nothing. Has anyone done this before? I was able to do it to my instrument panel and it worked but it was a different style light.

Just to make sure, LED'* are not connected the same way normal bulbs are installed. They need to have a resistor inline with them and are polarized.