1. Your climate control could have some broken solders. However, most likely, the lightbulbs on your climate control unit are loose or about to go. To replace, remove the wood cover (2 screws on top of the radio area). You will see a couple of tiny aluminum foil covering a couple of holes. That is were the lightbulbs are. Get a couple of replacement lightbulbs from the dealer. Get a rubber hose the size of the lightbulbs. Use the rubber hose to"hook and remove" the lightbulbs. Do the opposite to install the new ones. Of course there is the pro way to do it, disassembly, removal and replacement of the lightbulbs. I did it the easy way. It works!
2. I bought mine at the dealer. The number is on the hose, though. It is not expensive.
3. I used the harness. Perfect fit. It is free if you buy a car stereo from them.
Good luck!

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J.H.
'86 300E