Troubleshooting the Classic Auto Sound Becker tribute radio

I installed the Classic Auto Sound Becker tribute radio in my 250SE a couple of years ago.   The W111 series are supposed to have a slimline radio instead of a DIN size.   Unfortunately, a previous owner cut my dashboard to DIN size.   This meant putting the correct radio for the year was now practically impossible.   Instead of putting a 70s Becker instead, I went with this tribute radio which is based on a Retrosound radio with an actual Becker faceplate.

I’ve been happy with the radio in the car, and would recommend it to anyone who had their dashboard modified like this.    Recently, I’ve been seeing some strange behavior on the radio and it was getting less and less usable.   Classic Auto Sound, the company who sold it to me have been very helpful trying to trace what is going on.

The problems first started when on a long drive, the radio would stop responding to the buttons or knobs.   It would just keep doing what it was already doing.   In that case, it was playing off the USB key.    It would also sometimes not turn off properly when I turned off the ignition switch and removed the key.    At first this happened only on long drives, but in the last couple of months I couldn’t even power the radio on at all.   It would always be just stuck in the clock mode.   It would be like that even with the key off.

Classic Auto Sound suggested it might be the left knob shaft failing.   The suggested removing the radio, and connecting the plug from the right knob into the left side of the radio.    I did that, and all of a sudden I could turn the radio on and off again.    Based on that Classic Auto Sound sent me a knew shaft at no cost to me.   That’s great service considering the radio is a couple of years old now.

It’s pretty easy to swap out one of the shafts – I had it done in about 15 minutes.   I took the car on a short drive, and everything was well.       A couple of days later, I took the car on the MBCNSW July Night Drive.    The meeting point is about an hour and ten minutes away from where I live.   About 45-50 minutes into the drive, I noticed the radio stopped responding to inputs from the knobs.   I was using the bluetooth function, so I could still change tracks from my phone.   Normally you can use the radio knobs to do this.   I was also unable to change the volume.

While we were waiting for the final cars to arrive, I disconnected the battery and reconnected it.    The radio was fine again.   However, on the actual drive, it was a much shorter time before it stopped working again.   The drive was about an hour and 20 minutes and during that time, I had radio through my phone, but I could not just the knobs.    I didn’t bother disconnecting the battery while we got a snack at McDonalds at the end of the drive, I just paused the music with my phone.   The radio stayed on pause the whole time I was in McDonalds (about 20 mins).  It then played the entire way back, again through my phone with the buttons doing nothing.   Once I got back, it took disconnecting the battery to turn it off.

I emailed Classic Auto Sound again and asked if they had any more ideas.   It was suggested that I check if I have the yellow (constant power) and red (switched power) lines correct.   I checked those, and they were.  Voltage was 0nly present on the red wire with the key on, and was always present for the yellow wire, with the battery connected.

Once confirmed, It was suggested that I check the behavior of the switched power, as the radio isn’t supposed to work without it.   In order to be able to do that on a long drive, I’ve rigged up a voltage indicator to the switched power source.    It was less than $10 at Jaycar.    I’ll now be able to watch what happens on a drive when the radio is working fine, and if there is any difference when it is not.

The little voltage meter comes out from behind the dash, so I can see it on top of the transmission tunnel.   Next step is another longer drive in the car to see what is happening.