2003 Z4 Stock radio stopped working

[dn03z4red]

I need help ... I have the stock radio with CD player on my 03 Z4. The stock radio sounds pretty good and so does the CD. I have the 10 speaker system with the amplifier in the battery compartment in the trunk. The problem just started ... the radio and CD plays normal only when I don't start the engine. Once I start the engine, the sounds from radio and CD cuts off. No one seems to know what is causing it. There is power to the head unit once it happens except the sound stops. Has anyone had this problem with their stock radio unit? I really wanted to retain the originality of the car and wanted to get it fixed. If anyone have any knowledge why the sound cuts off when the engine is running ... please share your ideas and thank you in advance. -- DAN

[MarcoZandrini]

Check for power at the amp when the engine is running.

[dn03z4red]

There is power at the amp when engine is running. Also I noticed, the radio even powered up when I depressed the power button and sounds great even with the ignition not turned on (without key in ignition). But same results ... once I start the car the sound cuts off but the head unit still have power.

[MarcoZandrini]

That is odd. What is the voltage at the amp with the engine running? There is a wire that runs from the head unit to the amp that carries the “turn on” signal to the amp. You should be able to find it in here:

https://bmwteka.com/wds/en/e85

[dn03z4red]

[QUOTE=MarcoZandrini;30839646]That is odd. What is the voltage at the amp with the engine running? There is a wire that runs from the head unit to the amp that carries the “turn on” signal to the amp. You should be able to find it in here:

https://bmwteka.com/wds/en/e85[the voltage is at 14.2. I even had the voltage regulator replaced but still facing same issues]

[dn03z4red]

can the voltage regulator be overridden to accept 14.2 volts or be modified? I got the amp pulled again for some more bench test. when ignition is on accessories, the voltage is somewhere around 12 and radio and cd works fine. But when ignition is on start position and engine running ... power from the amp is cut off.

[MarcoZandrini]

And you’re having no other electrical/electronic issues? Where does the power come from? Is it straight from the fuse panel? This is very odd.

[dn03z4red]

I have no other electrical issues but the radio unit cutting off and power still comes from fuse panel... had the amp pulled once again for some more bench testing ... the amp technician working on it made modifications to my amp to accept the maximum voltage @ 15 and seems to have worked. Finally this issue is fixed, and it is a very odd, but I'm glad it is working now. Now I just need to get an FM modulator so I can have bluetooth streaming since my 03 BMW head unit only have CD player and no BLUETOOTH.

[MarcoZandrini]

Be advised that the amp requires a 12VDC “turn-on” signal from the head unit. If they signal goes to 0VDC the amp turns off. Dig through this website to find the wire that carries the “turn-on” signal: https://bmwteka.com/wds/en/e87