ELECTRICAL GREMLINS..........
I suppose you expect it really, being linked in the past to Lucas (Prince of Darkness....) the Landy was never going to be an electric work of art. Although things go wrong intermittently the bonus is its all pretty simple. I'm an electrical imbecile and if I can fix it anyone can.
Most common problem : turn one thing on and something else happens!
With me this was the lights, when I flashed them the wipers worked. Essentially I cured practically every electrical niggle by several small jobs. These were:
CLEAN THE CONNECTIONS. Pull out every connector bullet, clean it and reassemble ensuring a good connection is had. I also had some petroleum grease that I reassembled with.
CLEAN THE EARTHS. Even add new ones if needed. I found my earth strap from the battery to the chassis was not only cut/worn but where it was bolted down there was a mass of rust underneath almost preventing the connection. After I cleaned this up I notices that all of the lights on the motor were noticeably brighter! I also ran a second earth from the chassis to the engine block as there was not one present on my car. For lights you will find bunches of black wire screwed to the bodywork dotted around the vehicle. Unscrew them (if you can, I drilled some out) then clean where there going to go and reassemble tight.
CLEAN FUSES/RELAYS. Sound a little odd, but I have seen a few 13 year old fuses that defy belief. I threw a couple away that were very furred up to say the least.
CHECK FITTINGS. Lights were the worse for this again. Some of the indicator fittings were so bad I ordered a full new set of the smaller lights. This cost me about £30 and has probably saved me a lot of time tracing faults. Switches as well. Here you can see my light switch that had been re-soldered by a previous owner. The heat of the solder melted the plastic and the connection stud had sunk inside where the connector touched it. This had the effect that if you wiggled the switch the lights would flick on and off. Replacement was £15.
If your really serious and your keeping the vehicle for a while you could look towards fitting an earth bar somewhere and routing all earths back to one spot. Not as difficult as you would think and would be an excellent long term solution. As far as I know boats and some kit cars (fibreglass body) work on this system.
A common moan from Landy owners is the lights are crap. It's possibly worth remembering that even if you fit mucho-costo new lamps and your wiring and earths are still in poor condition, your fancy lamps will not perform as well as they should. Fix the basics before spending money on upgrades....