The LED clock on my 2001 Subaru Forester stopped working over a year ago. It worked only intermittently for a few months before that; sometimes it would be illuminated sometimes not. I despaired of ever knowing the correct time while driving until I came upon this thread in the Subaru Owners forum:

It turns out the relatively common problem is a bad solder joint on the clock circuit board and is easily correctible by simply resoldering it. The above link has step by step instructions with pictures. Be sure to check all the resistor solder joints (on the "300" and "510" resistors). In my case the 510 joint that is underneath the glass was clearly cracked. I had to remove the circuit board from the black plastic case to get to it (very simple - 3 tabs). I decided to resolder all the 300 and 510 joints for insurance against future joint failures. Took about 5 minutes. And now my clock works again!!! Saved over $80 for a replacement clock! Thank you Senor Subie!