Radio loses memory sometimes when starting

[John Winn]

Good Morning..I have a 1984 300SD and when I first got it I noticed that sometimes when I would start it, the radio would turn itself off(original Becker) and I would have to turn it back on. I recently put in a JVC stereo and it does the same thing, exept this one the computer inside gets confused and I have to push reset. It doesn't always do it but about 10 percent. When I turn the key to "on" and are waiting for the glow plugs it is fine..Go to start, then back to run, nothing. I have to get my ballpoint pen out and push the reset button on the radio. I know it isn't an ignition switch problem because the AC is running and I can reset the radio..It is like the Memory wire is losing voltage when cranking. Any ideas??Thanks! John

[stevebfl]

I can tell you a story that might shed light on your problem.

It might not as most electronics have gotten smarter in the years since this experience.

We sell Blaupunkt (and Becker) radios. About ten years ago we had a new installation do exactly as you describe. We put in another radio and it happened again. I'm not sure what we did next on this car but we soon had three cars running around with this same model radio and same problem and we were getting tired of changing the radios. And then... the battery failed on the first car, then the second, and then the third.

It was really cool, they had built a radio that (if we had realized sooner) exactly predicted battery failures be resetting the memory at the exact low voltage each of these cars had occur due to their poor batteries. In these cases that was about 8.5v.

It was interesting at the time and taught a lesson that becomes more important with each electronic device. Many control units loose their memories if disconnected from the battery and many only need to be disconnected down to below 9v.

Most new radios have to go much lower in voltage than that which will start a car but I have seen many a diesel drop battery voltage to near 8v and still start easily.

[Arthur Dalton]

Your starter may also be getting down on the brushes creating larger than norm battery current draw on start. This coupled with a weak battery will drop the voltage enough
to trip the radio low voltage circuit.
A battery draw test should be done.