So I was installing my new Blaupunkt Monterrey MP35 today, it went in pretty easily. Once I had the power and speaker wires connected, I had it turned on to listen to it while I finished up everything else. Then right before I was done, it quit working. This radio can play for a limited time with the car off, which is what I was doing, so its powered by the constant +12v wire. Well, after it quit working, I tested voltage at that wire and there was none. The illumination wire has 12v with the lights on and the red wire has 12v with the key on, but the constant no longer has power.

I looked at the fuse box and they all look okay, but I don't have a map of which fuse is which. Is there an in-line fuse for the constant +12v wire somewhere? I saw one on the red 12v wire for when the key is on, but not on the constant 12v wire.

Any help is appreciated...tomorrow when its stopped snowing I'll go out and mess around with it again. But if someone knows what's going on, it'll help a lot. Thanks!
-Geoff

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

I just done the same install earlier this week in my 82 300 sd with the same receiver.
I had the same problem you as you.
You have to connect the 2 brown wires that were connected to the back of the Becker. These are the chaise ground for the receiver. Connect them to the threaded post on the back of the Blaupunkt and you are good to go.

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1982 300sd

Ok, that makes sense. Only thing is the previous head unit was not the original Becker. I'lll go look for some brown wires...but if I can't find them, can I just ground the threaded post on the back of the receiver directly to the car?
Thanks again,
-Geoff

Oh, what's a chaise ground?

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

Yes, just run a ground wire from the post to a good ground on the car.
Oh, and I meant chassis ground.
Hope this gets you goin

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1982 300sd

I found my blown fuse. It is an in-line fuse for the constant +12v wire and the fuse is located under the shifter console, right next to the illumination in-line fuse. The constant 12v fuse is only 0.5 amp, and I think the red 12v line (key on voltage) is 1.5 amps. Probably the factory radio only used the constant line for the clock and memory, but this radio uses it to operate the radio when the car is off (and maybe when the car is on). I was going to put a bigger fuse in the line, but I can't find in the literature from Crutchfield or the radio manual that lists the fuse requirements. I might call one of them. But for now I'll try grounding the rear post and using another 0.5 amp fuse. At least now I don't have to pull the radio anymore

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now