FAQ
TL;DR: Poor FM after a non‑OEM swap usually means no 12 V to the rear‑window antenna amp. “There should be 12V on the white plug.” Fix power or a broken Fakra lead. [Elektroda, korek516, post #16830655]
Why it matters: This FAQ helps Passat B6 sedan owners quickly restore clear FM reception after installing Android/aftermarket head units.
Quick-Facts:
- Passat B6 sedan uses a rear‑window antenna amplifier that requires a 12 V feed. [Elektroda, Cinek_Barczewo, post #16830669]
- Two Fakra leads at the radio: white and beige; users reported testing only the white first. [Elektroda, brolypl, post #16830427]
- Factory VAG radios can log antenna “short to ground” or “open circuit” faults for diagnosis. [Elektroda, korek516, post #16830697]
- A common failure is a broken coax at the Fakra connector; re‑termination or replacement may be needed. [Elektroda, brolypl, post #16936088]
- On the sedan, the key amplifier is at the rear window; pillar units are typically left alone. [Elektroda, Cinek_Barczewo, post #16830472]
Quick Facts
- Passat B6 sedan uses a rear‑window antenna amplifier that requires a 12 V feed. [Elektroda, Cinek_Barczewo, post #16830669]
- Two Fakra leads at the radio: white and beige; users reported testing only the white first. [Elektroda, brolypl, post #16830427]
- Factory VAG radios can log antenna “short to ground” or “open circuit” faults for diagnosis. [Elektroda, korek516, post #16830697]
- A common failure is a broken coax at the Fakra connector; re‑termination or replacement may be needed. [Elektroda, brolypl, post #16936088]
- On the sedan, the key amplifier is at the rear window; pillar units are typically left alone. [Elektroda, Cinek_Barczewo, post #16830472]
Why does FM reception drop after installing a non‑factory radio in a Passat B6 sedan?
Most aftermarket radios don’t power the rear‑window antenna amplifier by default. The amp needs 12 V on the white Fakra line. Without that feed, sensitivity collapses and stations fade. Restore antenna power via the radio’s ANT/REM output or a powered separator. “There should be 12V on the white plug.” [Elektroda, korek516, post #16830655]
Which connector powers the antenna amplifier—white or beige?
Use the white Fakra. Community testing confirmed the white plug carries the 12 V feed to the rear‑window amplifier. If reception dies when you unplug white, you’re on the correct circuit. Confirm 12 V with a meter while the radio is on. [Elektroda, korek516, post #16830655]
How do I quickly test if the antenna amp is getting power?
3‑step How‑To: 1. Turn the radio on and select FM. 2. Measure between the white Fakra center pin and shield; expect ~12 V. 3. If 0 V, check the radio’s ANT/blue lead or separator power. [Elektroda, korek516, post #16830655]
Where is the main antenna amplifier in the B6 sedan?
It’s integrated at the rear window. The original poster accessed it there to test voltage and plugs. Focus diagnosis at this module before chasing other locations. [Elektroda, brolypl, post #16830427]
Do the pillar amplifiers matter on the sedan?
Leave the pillar units. The shared diagram guidance was to concentrate on the rear‑window antenna section for FM issues on the sedan. [Elektroda, Cinek_Barczewo, post #16830472]
Can the factory radio help diagnose antenna faults?
Yes. Reinstalling a VAG unit can surface DTCs such as short to ground or open circuit on antenna lines. That narrows wiring versus module faults. Clear, test, and re‑scan. [Elektroda, korek516, post #16830697]
I unplugged the white Fakra and reception died—what should I check next?
Check for a short or open in that cable. Inspect continuity end‑to‑end and flex the Fakra; internal breaks are common and kill signal even if the plug looks fine. [Elektroda, korek516, post #16830452]
Is 0 V at the rear amplifier normal?
No. The amplifier requires about 12 V during radio operation. 0 V indicates the head unit didn’t feed ANT power, the separator isn’t powered, or the feed is broken. Restore power first. [Elektroda, Cinek_Barczewo, post #16830669]
My Android unit “sort of” receives with a separator—why still weak?
Weak FM with a separator usually means only one antenna path is powered or the white Fakra feed is damaged. Verify the separator’s blue lead is live with radio on, then meter the white plug for 12 V. [Elektroda, brolypl, post #16830427]
How many antenna leads are behind the radio, and which to use first?
There are two Fakra leads—white and beige. Start with the white, since users observed reception changes and power expectations there during tests. [Elektroda, brolypl, post #16830427]
The coax is broken at the Fakra—repair or replace?
You can re‑terminate with a proper Fakra for the cable’s diameter, but oversized OEM coax may not fit universal plugs. Many owners replace the earned cable run to the amplifier for reliability. [Elektroda, brolypl, post #16936088]
Will a shorted antenna line damage the radio?
Factory radios flag the short and may shut antenna power, but reports focus on fault codes rather than damage. Fix wiring, then restore power and retest reception. [Elektroda, korek516, post #16830697]
What is a Fakra connector?
Fakra is an automotive RF coax connector family with keyed housings for radio/antenna modules. It maintains secure mating and consistent impedance in vehicles. [“Fakra connector”]
What tools do I need to diagnose this quickly?
Use a digital multimeter, Fakra release tools, and a powered antenna separator if your radio lacks ANT power. Measure 12 V at the white plug with the radio on. [Elektroda, korek516, post #16830655]
Any edge cases I should know about?
A hidden break inside the Fakra can pass a visual check yet open under flex, killing FM. Wiggling the lead during continuity tests often exposes this intermittent failure. [Elektroda, korek516, post #16830452]
What’s a simple fix checklist before rewiring?
Ensure the blue ANT/REM lead outputs 12 V, power the separator, confirm ~12 V at the white Fakra, and reseat connectors. If still weak, inspect and re‑terminate the Fakra. [Elektroda, brolypl, post #16830427]
