First things to check for in Flaky Electrics.

One of the first things to check for in keeping your electrics from being flaky are but not limited to the Following.
Bad Grounds/Earths connections.
Battery to frame to engine main cables checked for resistance/voltage drop.
New Battery ends will not make up for Green, dark brown, Corroded unshielded cables.
Solid brown wires left hanging, Tarnished, Corroded terminal connections on the Engine/Frame.

Keep your rain drains clean and clear, re-route wires/vacuum lines out of them, including the Windshield/Windscreen washer line that was usually run up the right rain drain.








Install a rain tray water diverter and a debris guard for the hood vents to prevent crud/leaves from plugging the Rain Drains, which are behind the strut towers.

Factory Debris guard.



Clean all attachment Studs, Nuts, Screws clean and shiny, as well as the body/engine part they attach to.

Verify that your Main Positive Cables are good as that will allow higher Current/Voltage to the Battery and starters, alternators, and motors working.

Cables are the last thing we look at usually, as I am as guilty as anyone else to get Snake bit by them. In My early in my experience with electrics, Shark bit.
Gotta Love Lucas in the 50's 60's and 70's British Leylands that I drove and early Dubs.

Antenna replacements that didn't have a drip stop loop that allowed water to travel on to the Fuse panel.  "Windshield Rust" between the Seal and the glass that allow Water migration in to the fuse box.

Antenna Drip Stop.


Re-seat all fuses occasionally no matter how hard they can be to get to. The fuse never blew, but the holder got FRIED. This is for the AC on my 93.




Seal any and all grommets or replace them and Cables that enter the Cabin from the rain tray and behind the Shock mount areas.

Verify clean all connectors as you work about your car, as  taking them apart or off and reconnecting/inserting then will cause cleaning the connections, and possibly push connectors out causing a intermittant or open connection which can confuse most every one, use a small screw driver to make sure all pins in all connectors re-seat fully.

Why:


Here are some helpful things on the Cabriolets that I have found over the years.

Quick Ground Test
https://www.volkswagenownersclub.com/threads/brianos-quick-grounds-test.134637/?post_id=765374#post-765374

Cluster Grounds
https://www.volkswagenownersclub.com/threads/improving-your-cluster-connections-and-ground.24949/?post_id=753377#post-753377

Parasitic battery drain
https://www.volkswagenownersclub.com/threads/battery-parasitic-drain-diagnosis.128646/?post_id=752813#post-752813

Ground Effects
https://www.vwvortex.com/threads/ground-effects-and-the-repair-of-your-car.5284503/

Alternator tune up
https://www.volkswagenownersclub.com/threads/mk1-bosch-posted-alternator-tune-up.135143/

Relay your headlamps
https://www.volkswagenownersclub.com/threads/relaying-your-head-lights.32215/

Heat soak starter fix.
https://www.cabby-info.com/files/ignition/InstallingHot-startRelay.pdf

Relaying your Head Lamps and your Starter are quick ways to off load Jigh Current draw through your ignition switches, and head light switch making them last longer and not Burn out.