help dimming my LED's

[tonkaman]

ok so i dont know a lot about LED's but here is my problem. i have a 1990 K1500 Chevy pickup i have recently changed out all the lights in my gauges to LED's and they will not dim, i know these lights are dimmable cause ive seen them do it. when i first got the lights i only installed 2 of them and left the other 5 lights as incandecents, the 2 leds dimmed until i changed out the other 5 to led, now none of them dim. i was told if i put at least one regular light back in the circuit the leds would dim, so i did that and still no dimming. what can i do, they are hooked up to the stock dimmer switch in my truck obviously.

these are the lights i installed http://www.superbrightleds.com/cgi-bin/store/index.cgi?action=DispPage&Page2Disp=%2Fspecs%2FWLED-xHP5.htm