How hot should a Becker radio get?
 

I removed the Blauphunkt AM/FM/Tape deck in my latest 1983 300SD and installed a used Becker radio that is from the same era and style vehicle. I noticed during testing that the unit got quite hot on the side facing the driver. It was hot enough after maybe 10-15 minutes that I risked a burn if I touched it. Having nothing to compare it to as my other 300SD is in the paint shop, I'm not sure if this is normal or not. I know they get warm but how warm is the question. I also noticed that the LCD display is missing a character and after 20 minutes of driving, the left side audio channel cuts out. It is probably over heating and I need to find another unit. I have a 3rd Becker but guess where it is? Yep, Maaco, on the floor of the 300SD...

That's too hot for sure.

They have incandescent bulbs for illumination so they will get mildly warm but not hot.

Unless the sun is beating down on it?

I would send it off to Ed at Becker, chances are he can repair it. Not cheap (I would plan on $150 minimum) but worth it. Becker Autosound Website

Well, to be clear, I reached under the radio where the ash tray would be. This was before I reinstalled all the other bits. The front face of the radio only gets warm but far from a concerning temp. The underside, back is concerning.

That sounds too warm. The only guess I can make (and it is a guess) is that the car's speakers do not correctly match the impedance that the radio is expecting to see. That might cause the output transistors to overheat. Over time they could be damaged.

Jeremy

Are you sure you have the wiring correct?

Was the blaupunkt you replaced it with, one that has the separate amp? I am looking for one with knobs...as the one I have lost them many moons ago...

Left channel cutting out is your clue. Unplug the left speaker wires (front and rear) and see if the overheating stops. If it does, look for shorts in your wiring.

Valid point but the radio seems to start getting hot before anything cuts out. If it was a constant short, would I not expect to always have 1 or more speakers not working?

The previous radio was a Blaupunkt Limited 1290 "High Power 2x25W." No clue if there is an amp. The Blaupunkt radio harness used the factory connectors. I connected the black female spade to the male spade next to the 4 pin connector on the Becker. The hot lead female spade was connected to the male spade on the 4 pin harness; grounds and speaker leads to their obvious connections.

It may not be a zero ohm short but a partial short or mis-wire to the left speakers. Take a resistance measurement of the left and right radio speaker connectors, they should read similarly and not less than 4 ohms. You can also take resistance measurements of the radio speaker outputs and compare left and right channels. Keep meter polarity the same. Reverse the meter lead polarity also, which will give a different reading.

Heres a diagram with the color wires for the plug

http://www.benzworld.org/forums/atta...00565341pm.jpg

Besides the plug, you should have one spade connector and that is for the antenna trigger wire...the speaker plugs are european style and no way to get those mixed up...unless they were cut.

With the fader in the center position, I measured the speaker wires behind the radio. Both were 2.1ohms.

I guess I will reinstall the Blaupunkt radio for the time being and check if the speakers are original or not. It's kind of hard to do in the front with the dash cover over part of the speaker grille. I have some Gen 2 W126 speakers that may work.

Once you remove the Becker, bench test it w a 12 V power supply and two loose car speakers.
Find out what gets warm and hot.
If you felt the heat while driving, could it have been heat up from the trans?
My 300d was like that. I put in a piece of insulation to heat shield it.

That's not a bad idea at all.

The car was not even running when I felt the radio get hot.