As you are planning a long distance trip I strongly recommend you ensure your RR has the correct, larger sized battery. Stealerships and used car lots always put the cheapest battery they can find and even used ones just to get a car off their lot. If the battery is the correct size and at least 800 CCA or more charge it off line, i.e. with the terminals disconnected. While they are, touch and hold them together for 10 - 20 seconds. This will ground and drain lingering bus error codes so that when you reconnect the battery the bus modules will know nothing and have to relearn as you drive. A process that takes about 30 - 50 miles of driving. Corrupted codes get passed around the bus contaminating the logic in modules that shouldn't care. By starting with a blank page and a well charged battery any errors codes will be new and relevant.
After I'd dried out my soaked electronics and installed the LR factory 'plastic mackintosh' over them, a cheap bit of plastic to keep the water leaking in from draining through the GPS DVR, stereo amplifier (Man, you should have heard the loud banging from the speakers the day the rains came in) I'm glad to say everything still worked. I sprayed all the electrical contacts with DeOxit followed by WD40 after it had dried out. Spray all the fuses too. Don't be shy with it. Since I did all the above, and ensure my battery is maintained above 13V, my bus error codes have all gone away.
BTW, the main source for the water that drains down into the left rear corner electronics stack is nearly always the sun roof drains. They become clogged where the pipes come out of the rain accumulation trough. the fronts are easy to clear using a length of Cat 5 network cable. Be gentle to avoid pushing the flexible pipe of the drain spigot defeating the purpose for it's existence. Don't be tempted to use an air gun. That is guaranteed to blow the pipes off. The biggest problem are the two rear drains. It is challenging to access them so they often remain clogged or get pushed off the spigot when someone uses a long stick to rod the drains
Most sunroofs will leak a little which is why they come with drains attached. Water that enters accumulates in the sun roof frame troughs and is supposed to leave via the drains, the front when braking and the rear when accelerating. Mine was so bad that one morning I came out, got in the car and drove off down my street. It had been raining heavily all night but was dry then. As I accelerated I heard water gushing back above the headliner. I pulled over and quickly removed the access panel in the left rear to see water draining down over the LR 'plastic mac' I'd installed.
Our cars are great cars. I still get a lot of admiring comments despite their age. Most people, myself included still think our generation of RR are the best looking they have made to date. So it's worth putting the effort in to keep them running. I'm hoping the guy at Classic RVs in the UK comes through with his planned EV conversion. I'm ready!
Oh, and try to avoid turning on the demister fan, screen heater, seat heater(s), steering wheel heater, heated mirrors, radio, GPS, heated rear window, windsheild wipers front and rear, etc., etc.while the engine is just idling after cranking the engine to life. You would be amazed at how low the available voltage can drop until you get out on the highway. Those poor little can bus modules get starved of juice and their poor little CMOS memories just make mistakes, dropping bits left right and center. And we expect them to never make a mistake while we deprive them of the power then need to get their work done.
