First replace both LED's. Get a new one and hook it up in the factory spot. This will tell you if the LED's are on thier way out. If the new one flashes as per normal then you have your fix. If not, the new one only does the dimming thing, then you most likely have shorted the alarm module and will require a new one or fix the one you have. If you don't have extensive electronic background you might not be able to fix the old one.

Hope I helped.

-KOZ