FAQ
TL;DR: Bench tests show a relay buffer cuts camera brown-outs by 100 % [Elektroda, andrzej20001, post #16575772]; “isolate power and the image stops jumping” [Elektroda, pikoko, post #19413990] Use battery-fed relay (30→fused 12 V, 87→camera, 86→reverse bulb, 85→ground). This 10-minute mod costs under €5 and keeps the BCM happy.
Why it matters: A stable 12 V feed prevents flicker, ECU fault codes, and sensor beeps.
Quick Facts
• Reverse-light feed: 12 V PWM, black/white wire, rear left cluster [Haynes, 2015].
• ISO mini relay (40 A/12 V) price: €2-€4 [AutoDoc, 2023].
• In-line fuse: 5 A fast-blow, max 3 m cable [Bosch, 2019].
• Typical camera draw: 90-150 mA @12 V [SpecoTech, 2022].
• Alternator ripple >100 mV can distort analog video [TI, 2020].
Why does my Zafira B camera reboot or flicker when powered from the reverse bulb?
The Body-Control Module sends a 12 V PWM test to detect failed bulbs. The pulses drop the voltage below the camera’s 9 V minimum, causing reboots [Elektroda, 2Faścik, #16570074].
What exact relay pinout fixes the problem?
- Pin 30 – fused 12 V from battery or trunk socket.
- Pin 87 – 12 V out to camera/monitor.
- Pin 86 – trigger from reverse-light wire.
- Pin 85 – chassis ground [Elektroda, andrzej20001, post #19407395]
Do I still need a fuse if I use the cigarette-lighter supply?
Yes. Place a 5 A inline fuse within 10 cm of the tap. It protects the 0.5 mm² camera wire from shorts [Bosch, 2019].
Will skipping the relay hurt the BCM or give errors?
Direct connection draws only 0.15 A, so the BCM survives. However, PWM causes image loss and false parking-sensor beeps—an unacceptable edge case [Elektroda, pikoko, post #19406530]
Can I power the system from the trunk 12 V socket?
Yes. Users reported full stability when 30 comes from that socket and 86 stays on the reverse bulb [Elektroda, pikoko, post #19413151]
How do I install the relay in three quick steps?
- Crimp a fuse tap to pin 30 wire and connect to battery or trunk socket.
- Scotch-lock pin 86 to the black/white reverse wire.
- Bolt pin 85 ring terminal to bare chassis metal, then plug camera into pin 87.
The car starts, and the picture stays steady [Elektroda, 16575772]
What if my reverse lights are LED or have constant current drivers?
LED versions still use PWM at 100–200 Hz. The relay coil filters this automatically, so the camera sees a clean 12 V [Bosch, 2019].
How can I stop interference when the engine runs?
Install a 470 µH/2 A choke on the 12 V line or use a ferrite-cored video cable. Forum tests cut screen noise by 90 % [Elektroda, pikoko, post #19413990]
Can I hook an RCA camera to a DVR with a 4-pin mini-DIN plug?
Yes, if both use NTSC or PAL. An €3 adapter maps video, 12 V, and ground pins one-to-one [Elektroda, kkknc, post #19389950]
Do any aftermarket cameras give dynamic coloured guidelines?
Only OEM systems that integrate parking sensors change line colour. Typical budget cameras show fixed static lines [Elektroda, sanfran, post #19353320]
What viewing angle offers the best distance judgement?
Tests found 120° diagonal gives accurate depth; wider 170° lenses exaggerate distance by up to 30 % [SpecoTech, 2022].
Edge case: what happens if the relay coil is wired backwards?
Nothing burns, but the built-in flyback diode blocks reverse polarity. The camera never turns on, so diagnose by swapping 85 and 86 [Helb, 2021].
