Engine bay Earth connections (sticky?)

I had electrical problems - they've all (touch wood) gone away, as a result of cleaning up earths and electrical connections in the engine compartment. I hope the following will be instructive for anyone else with similar gremlins.

Problems (not an exhaustive list)

• Malfunctioning headlights (dipped and main beam reversed)
• Instrument lights malfunctioning (temp light on/off intermittently, almost all dash illumination switched off if headlights switched on)
• MFA malfunctioning (went dead if headlights switched on, plus generally underperforming  - no sensible MPG figures)
• Engine reluctant to start (solenoid operated with audible click, but starter refused to operate in four out of every five attempts).
• Slow windscreen wipers

Solutions and results

• Cleaned and reconnected the engine bulkhead earth strap and brown earth wire to valve cover

 RESULT - Headlights and instrument lights worked, MFA improved, but other problems still present

• Cleaned up ALL main electrical connections as follows;

Removed battery and disassembled battery connectors, cleaning off grease, wire brushing off any rust/oxide deposits back to clean metal for ALL connectors (main +ve and -ve and other connectors).

Cleaned all spade terminals on engine and ancillaries;

• Oil pressure sensor on side of engine (DX code)
• Oil temp sensor on oil cooler
• Oil pressure sensor (number two) on oil cooler
• Water temp sensor on outlet flange
• Spade terminals (x2) on Solenoid

Replaced spade connectors and cleaned up loom to alternator

• Disconnect alternator, open up connector on loom to access grubby spade terminals inside, cut off and replace, making sure to leave enough spare wire to reach alternator. Clean up spade terminals on alternator and check brush length. Reconnect.

Cleaned main terminal on solenoid

• removed nut, wire brushed contacts back to bare metal - re-assembled

Cleaned main earth lead

• Disconnect earth lead from battery, remove battery,
• lift coolant reservoir out of mounting without disconnecting,
• disconnect intake trunking and valve cover connection from airflow sensor unit, undo clip at back on bottom of sensor unit and lift to access the two bolts underneath which connect the main earth lead to chassis and to engine mount plate (you will need a long socket extension plus universal joint to access these, plus a healthy dose of patience). Undo these bolts, remove earth lead and wire brush clean ALL connections on lead, on mountnig plate and on chassis (small plastic wire brushes sold in ?1 shops ideal).

Re-assemble

RESULT

• Engine spins like a jet turbine on EVERY turn of the key, and starts reliably every time.
• Lights work perfectly
• Wipers faster
• MFA has remembered that it's supposed to measure MPG, gives oil temp, no buzzing in cockpit.

Summary - If you've got gremlins, CLEAN EARTHS FIRST! Even if you've grown accustomed to quite enjoying the uncertainty, will it/wont it start?, and you've perfected the "I don't care if my golf isn't reliable, I like it" rebuff to smug owners of new cars, you may well discover the reliable golf that rolled off the production line 20+ years ago lurking underneath its temperamental alter ego.

AliCabrio