FAQ
TL;DR: To restore W211 under‑radio storage with an Android unit, you need an approx. 2‑second pulse—"gives an impulse of about 2 seconds and reverses polarity"—driving the motor via the factory button. [Elektroda, CameR, post #20038551]
Why it matters: It lets you keep the stock button and smooth open/close without the OEM head unit.
Quick Facts
- The compartment is the CD changer bay; the OEM radio triggers the mechanism after a button press. [Elektroda, tazz130, post #17281686]
- After an Android swap, the storage stops opening, while other front‑panel functions still work. [Elektroda, CameR, post #17276349]
- OEM‑like behavior needs a momentary‑button controller that alternates polarity and runs ~2 seconds per press. [Elektroda, CameR, post #20038551]
- An AVT current‑sensing kit was noted; it stops the motor when current rises at end‑of‑travel. [Elektroda, jdubowski, post #17286073]
- A DIY using two NE555 blocks (toggle + polarity control) was reported working. [Elektroda, janosiksik, post #20388809]
What is the W211 under‑radio storage and how is it controlled?
It is the CD changer compartment. In factory setups, the original radio controls the opening mechanism after it receives the front‑panel button press. With the OEM head unit present, the radio issues the command and the motor runs to open or close. [Elektroda, tazz130, post #17281686]
Why doesn’t my storage open after installing an Android radio?
Because the OEM head unit provided the control logic. After the Android swap, the storage no longer receives the open/close command, even though other panel functions still work. The original radio opened the box normally; with the non‑original radio it does not. [Elektroda, CameR, post #17276349]
Can I drive the mechanism with a simple switch and relays?
Yes. A basic solution reverses motor polarity using a rocker switch and relays, just like an electric window motor. This toggles direction to open or close the compartment. It is a straightforward polarity‑reversal driver for the DC motor. [Elektroda, CameR, post #17286044]
How can I keep the factory button and mimic OEM behavior?
Use a controller that, on each button press, reverses polarity and powers the motor for about two seconds. As one expert noted, it should "give an impulse of about 2 seconds and reverse the polarity" for alternate open/close cycles. This preserves one‑button operation. [Elektroda, CameR, post #20038551]
Is there an AVT module that auto‑stops the motor at end‑travel?
Yes, a referenced AVT kit cuts power when the motor current rises beyond a set threshold. "The drive shuts off when it detects a rise in motor current above the set threshold." That behavior acts like an automatic end‑stop without limit switches. [Elektroda, jdubowski, post #17286073]
Do you have a link to the AVT kit mentioned?
No link was provided later in the thread. The poster noted they would have had it in 2018, implying it was once available but not linked in 2022. Search terms were not shared in‑thread. [Elektroda, jdubowski, post #20038261]
Can I build a working controller with NE555 timers?
Yes. A member reports success using a 555‑based button stage plus simple polarity control on another 555. He confirmed, “I built it and it works.” This approach replicates the toggle and timed drive without the OEM radio. [Elektroda, janosiksik, post #20388809]
What pulse length should I configure for the motor run?
Set an approximate two‑second motor pulse per button press. That duration gives enough time to open or close without overdriving. The same guidance was stated for achieving alternate open/close with one factory button press. [Elektroda, CameR, post #20038551]
My motor runs on the bench, but with the box it hides then does nothing. What’s wrong?
This symptom suggests the assembly reaches a stop and the system no longer drives the motor, or there’s added mechanical resistance. Verify smooth travel of the compartment, check guide rails, and re‑test with brief timed pulses. The report matches “it hides and then nothing.” [Elektroda, dawidszymanski92, post #20391780]
Where can I get the wiring diagram (WIS) for the panel and module?
The thread did not provide WIS diagrams. A contributor lacked WIS access and therefore had no module or cassette schematics to share. You’ll need WIS or equivalent service documentation to obtain official wiring. [Elektroda, tazz130, post #17281686]
How do I wire an OEM‑like controller using the factory button?
- Use the panel’s momentary button to toggle a latch stage.
- On each press, output a ~2‑second motor pulse.
- Alternate polarity each cycle using relays, so the box opens and then closes on the next press.
This preserves one‑button operation. [Elektroda, CameR, post #20038551]
Do the other front‑panel buttons still work after a head‑unit swap?
Yes. The emergency, heated seat, and similar buttons remain functional after the radio change in the reported case. Only the storage open/close behavior was lost with the non‑original head unit. [Elektroda, CameR, post #17276349]
Can I repurpose a window‑motor style controller here?
Yes. The needed function is identical to reversing a 12 V DC window motor. A polarity‑reversal driver controlled by a button will open and close the storage reliably when timed correctly. [Elektroda, CameR, post #17286044]
