My BMW E36 Radio Keeps Turning Off and Asking for Code - Even After I Enter It

[E36Ron]

I love my 1996 E36 cabriolet with standard business radio and 6-CD changer in the trunk.

After 16 years of ownership and loving (and expensive) maintenance of the car, the radio has started acting up:

1. I push the volume button to turn it on, and it asks me for the 5-digit code, as if it had been disconnected from power.

2. I have the code, and I enter it. The radio comes to life, with all memorized stations intact, and plays fine.

3. After about 10 to 15 seconds, the radio shuts off, and the screen goes blank.

4. Pushing the button again does not immediately start it, I might have to wait another 10+seconds.

5. Then the cycle repeats -- enter code, radio is on for 10 to 15 seconds, then shuts off. Once in a long while, it will stay on for the duration of that particular trip, but then the problem will start all over again upon the next ignition cycle. (Sometimes it will come right on, then shut off and repeat.)

This is a tricky problem to pose to Google with any hope of getting a useful answer. Ditto Perplexity, suggesting rarity of the issue and no answers. The couple of forums where someone did pose this question as far back as 2008 or 2009 ended with no answers, and I haven't found anything more recent.

I have inspected the back of the radio, and everything looks clean, tight and new, with a big plug on the left, and another single heavy wire and small round plug over to the right. The question is, is the problem inside the radio head, or is it in the module from which power is fed to the radio in run and accessory mode?

This doesn't feel like any kind of fuse behavior, although I will check the radio fuse and update this post.

But meanwhile, does anyone have any ideas re the cause?

-- E36Ron

[82eye]

sounds like the memory circuit breaking down. they all get old and fail eventually. requires professional electronics intervention. it works on stored voltage and input/output signal. after time the radio can't hold on to the voltage and bricks itself.

[E36Ron]

Any recommendations as to professional repair for these?

[82eye]

Any recommendations as to professional repair for these?

maybe call german audio tech. parts for a lot of 90's electronic stuff are no longer available.

[E36Ron]

maybe call german audio tech. parts for a lot of 90's electronic stuff are no longer available.

Thanks for the suggestion! Looked into German Auto Tech on the west coast, found they are unreachable by phone, and have developed a rather poor rep in this forum. Nevertheless I emailed them.

Another option I found was Factory Car Stereo Repair Inc in Ft Myers, FL, www.carstereohelp.com, to whom I am reaching out, will report back.

Meanwhile, checked all fuses, including the one at the back under the locking connector, all good.

Regarding your explanation above, "sounds like the memory circuit breaking down. they all get old and fail eventually" can you be a bit more specific?

Conceptually, which memory circuit, and how is it supposed to work in this case?

-- E36Ron

[gc325is]

There are three power lines to your radio. One is a constant 12 for memory retention and one with the fuse in the back for radio power that only is powered when the key inserted. the other has available power for the light display illumination. If pin 9 has power all the time your radio internal may be damaged, mainly the memory retention circuit or even a capacitor or corroded line trace. What radio do you have? is it the hard to find CD or the common tape deck that may be gotten for $100

[Qfbohc83]

I had the same thing happening. It was a fuse. Took a while to figure out since it seemed to have power.

[E36Ron]

gc325is:

The pinout on the 1996 car is slightly different than that you kindly provided for the 1995 car, due to the addition of an I-Bus connection and a speedo input to automatically increase volume at higher road speeds. (!)

However, power appears on Pin 9, Hot at All Times, Pin 5, Hot in Acc, Run and Start, Pin 13, switched illumination, and Pin 15 is still Ground.

Interestingly, the voltage with engine running at Pin 5 (ignition switch) is a full 0.16v lower than that at Pin 9 (constant voltage).

Also, when the radio cuts out, the on-off switch remains inoperative for a variable period of time, after which it returns the code request. I'm trying to figure out which power supply line enables the on-off switch, and which maintains the history of the code across an ignition switch recycle.

Would those be Pins 5 and 9, respectively? In that case, the fuse behind Pin 5 might be suspect, even though it looks perfectly fine. This might also account for the reduced voltage on that line.

I also examined the innards of the radio, and it looks brand new, clean, with no apparent capacitor leakage or PCB deterioration, so I am leaning towards some sort of intermittent fuse problem, unlikely as that may seem. Next step will be to replace F44, the Pin 5 fuse.

-- E36Ron

PS, Qfbohc83:

You wouldn't happen to remember which fuse it was?