Fuse issues on vauxhall 1.0 2002 reg

Question edited for maker. Guessing you are in South Africa? Please always include FULL 'year make model' as the first three words in a question.

There are 3 Headlight relays hidden in the dash.

Opel (Vauxhall) Vivaro A (1G) - fuse and relay

https://fuseandrelay.com > opel > vivaro Location of electronic units - Let's highlight the fuse responsible for the cigarette lighter. Opel vivaro. The design of the boxes and the number of ...
‎Location of electronic units · ‎Passenger compartment · ‎Fuse box · ‎Relay box

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Your code 21 is just telling you that your left sidelight is out. The shaking and juddering is a different issue and needs a pro grade scan tool computer to see which sensor needs replacing.
21 Failure of left sidelight.

Vauxhall Astra Fault Codes - - Driving Test Tips

https://www.drivingtesttips.biz > fault-codes
Vauxhall Astra Fault Codes List ; 21, Failure of left sidelight. ; 22, Failure of right sidelight. ; 23, Failure of reversing light. ; 24, Failure of number plate ...

There does not appear to be a dedicated fuse for the reverse light but it possibly shares the fuse for the cigarette lighter. It is fuse 29, (20 Amp), in the fuse box in the engine bay.
Try this website to show where each fuse is. **NOTE** ALWAYS replace a fuse with one of the same rating.
https://fusesdiagram.com/opel-vauxhall/fuses-and-relay-opel-vauxhall-corsa-d.html

Try instrument panel fuse 17, AuxiliaryPower Rear. ...The instrument panel fuse block is located on the passenger side panel of the center console. To access the fuses, open the fuse panel door from the passenger side by pulling it out.

Michael: You may be having two separate problems. One owner says fuse # 20 operates the cigarette lighter. Usually when your car will not go in reverse, there is a problem with the transmission.

a fuse number 24,,,
The following specifications are for the Ford Contour and Mercury Mystique manufactured throughout 1995-2000.
Fuses Rating Color Circuit Engine bay fuse box 1 80 Black Power supply to main fuse box 2 60 Yellow Radiator fan 3 60 Yellow ABS 4 20 Yellow Daytime running lights 5 30 Light green Fog lamp 6 30 Light green Not used 7 30 Light green ABS 8 30 Light green Air pump 9 20 Light bue PCM module 10 20 Light bue Ignition switch 11 3 Violet PCM memory 12 15 Light bue Horn & hazard flasher 13 15 Light bue Oxygen sensor 14 15 Light bue Fuel pump 15 10 Red Right-hand low beam Passenger compartment fuse box 16 10 Red Left-hand low beam 17 10 Red Right-hand high beam 18 10 Red Left-hand high beam 19 7.5 Brown Heated door mirrors 20 10 Black Windshield wipers 21 30 Light green Electric windows 22 7.5 Brown ABS 23 15 Light bue Reverse lights 24 15 Light bue Brake lights 25 20 Yellow Door locks 26 20 Yellow Main light 27 15 Light bue Cigarette lighter 28 30 Light green Power seats 29 30 Light green Heated rear window 30 7.5 Brown Engine management 31 7.5 Brown Instrument pannel lights 32 7.5 Brown Radio 33 7.5 Brown Front and rear sidelights (left) 34 7.5 Brown Interior lighting & clock 35 7.5 Brown Front and rear sidelights (right) 36 30 Light green Air bag 37 30 Light green Heated blower 38 Unused Relays Color Circuit Location Engine bay fuse box R1 Green Daytime running lights (Canada) R2 Black Radiator fan (high speed) R3 Blue AC cut-out R4 Brown AC clutch R5 Dark green Radiator fan (low speed) R6 Yellow Starter R7 Brown Horns R8 Brown Fuel pump R9 White Low beam headlights R10 White High beam headlights R11 Brown PCM power supply Passenger compartment fuse box R12 White Interior and courtesy lights R13 Yellow Heated rear window R14 Yellow Heated blower R15 Green Windshield wiper motor R16 Black Ignition R17 Unused R18 Black One touch window switch Driver's door R19 Blue Cruise control cut-off Central fuse box bracket R20 Unused R21 Unused R22 White Fog lights Interface module bracket R23 Black Turn signals Steering column R24 White Left-hand flasher Door lock module bracket R25 White Right-hand flasher Door lock module bracket R26 Unused Bulbs / Lights Wattage Type Low beam headlamp 55 9006 Halogen High beam headlamp 55 9005 Halogen Parking / Side light 5 2357A Wedge Front turn signal 21 2357A Bayonet Rear turn signal 21 1157 Bayonet Tail light 21 1157 Bayonet Stop light 21 1157 Bayonet High mount stop light 5 2723 Bayonet Fog/Driving light 55 893 Halogen License plate 5 6418 Festoon Reverse light 21 1156 Bayonet Front sidemarker 5 2357A Wedge Glove box Map light 5 64111 Wedge Dome light 10 6411 Feston Step/Courtesy light Trunk/Cargo area Engine compartment 10 89 Wedge Instrument-general Automatic trans indicator

Pull each fuser out if the fuse box lid doesn't show a cig on the fuse lid and see if it's blown. Replace the blown fuse. If all the fuses look good trace the lighter back to the inline fuser and replace.

It`s the reverse light switch under the bonnet had to replace it on my 16v t reg corsa costs about 8-£10 and comes off easily because it`s just a bolt with electricals leading to the back lighting. This happens on every Corsa. Let me guess Your Heater control lights and fan swich lights have gone too on the interior. Any problem corsa related, been there done it.

The 1997 SL2 has a fuse for the cigarette lighter in a panel that is next to where the left foot of a passenger would be. The panel just pops off - held on by velcro.