2000 320 clk--outside temp light is out...how do I replace it?

check the operation of the light module.

there should have a fuse layout or description in the fuse compartment near or under the light switch.

pull out the instrument cluster by using the dash removal hooks. can be bought from mercedes dealer on any tool dealer like snapon or mac. all u do is to insert the hooks on either side of the instrument cluster usually on yhe lower sides and u will feel the hooks grab th instrument cluster. carefully pull the cluster out and disconnect the plug. you might have to have the steering wheel in the extended position to slide out the clucter. once you have the cluster out replace the bulb directly behind.

its a warning that the light is stuck on
it could be caused by the earth or grounding is faulty may just need to remove bulb 7 put it bak in it may fix it & the warning should dissapear

You can buy a replacement ambient air temp sensor at an auto parts store for about $10. Its as simple to change as a light bulb and can be found behind your front bumper at the base of the radiator.

does your car have parktronic-possibly a parktronic sensor. if not more than likely an outside temp. sensor. probably plugs into your tow hook cover on the front bumper. If there is a light bulb in the socket the only one that comes to mind is your side marker lamp. the lens pops out and the bulb socket pushes in and turns to secure the socket

these displays ared l.c.d. displays and what happens is over time the vacuum pack on the crystal element ruptures and get air in the tube and that part of the display is ruined permanently.I'm not sure if your saying that there are pieces missing or if the whole display is blank. If there are peices missing the only way to fix it is to repkace the instrument cluster. If they are blank it is very likley it is either the backlighting bulb or the dimmer switch. If you take a blanket and cover your display and can see the display very dimmly try replacing your back lighting bulbs- hopefully it is just your backlighting because the clusters are about 1,000 dollars and have to be special ordered with your mileage engraved in the new unit.

behind the control panel

They can check the battery and the charging system for starters. Fully charged battery,clean cables. then do a load test on the battery. If it didn't pass the test replace it and check the charging system.
Charging system easy to check , Put voltmeter on battery terminals and monitor vehicle's voltage with and wthout accessories on. should be between 13.5 to 14.5v . Before condemning alternator inspect wiring behind alternator ...if corroded replace then retest.
If voltage is with range then the problem is in the power distribution compartment/ relay, or either is a ground all those items share.