Radio power drain 1983 Mercedes 300D

[ron59b]

1983 Mercedes 300D, 286,000 miles

I purchased my car a couple of years ago and it did not have a radio. I purchased an after market radio and installed it myself. The radio I purchased has AM/FM/CD Player. I have twice had problems with the main power line causing an electrical drain on the battery.

The first time I actually took the car to the shop and had them discover my problem. The second time I discovered the problem myself. I have connected the main power line to two different sources for power. The last time I used a hot wire that was ran from the fuse box directly to the radio. Each time, once the wire was disconnected the electrical drain was non-existent.

I would like to know if anyone could recommend the proper HOT wire to use as a main and continuous power supply for the radio, which will not put a drain on my battery. Remember I am a DIY person and may not completely understand an answer that is too technical.

[cphilip]

The constant hot line should ONLY be drawing enough to keep the memory in the radio. All else should be drawing from the Keyed hot wire when its functioning. If your charging is sufficient, you should not be losing enough from the memory of the radio alone to cause problems (Unless it sat for months or something like that) so I suspect you have some other draw as well, or more likely an insufficient charging system going on. It is perfectly normal for a radio with some memory function to be drawing a tiny bit of power. If its so much that it deadens your battery then either the battery is not getting charged enough or the radio has some defect I would think. The Radio should have a constant hot and a keyed hot as well. And only work from the Keyed hot but yet keep its memory by the Constant hot.

No matter what you do, there has to be a drain if you want that radio to retain its memory settings and stations and clock (if it has one) but it would be very tiny draw. Something else is wrong if its causing a dead battery fairly quickly.

It should not matter where you get the hot lead for the radio. If the radio is drawing enough to kill the battery I would suspect a problem with the radio itself or a "soft" ground someplace in the wiring. If you are convinced the wiring is not shorting out, I would just replace the radio.

[ron59b]

Could you better explain "soft ground", I think that may be my problem. The first time i had it in the shop, I got it back and ran a separate ground wire to a screw in th e console. Can you recommend a better connection to use for ground?

What is the best type of wiring ot use for a ground?

Ron