Fuse and relay box diagram Opel/Vauxhall Astra G Fuse box diagram (Astra G since 2001). fuses and relays are coded as follows. R1 . R2. Horn relay. R3. Headlamp high beam relay. R4. Rear screen wiper relay. R5. Door mirror heater relay. R6. Fuse and relay box in the engine compartment Astra G. located. fuse box diagram. early models. late models.