Unofficialbmw.com

Arne · Joined: 10 Jan 2003 Posts: 1454 Location: Oregon

Hey guys (and gals), I'm back for a question. The factory head unit (CD33?) in my '96 328i has started having problems on FM only. Sometimes it works, and sometimes it doesn't. Often it will start working after everything gets good and warm, and once that happens it will work normally for as long as it stays warm. The problem only affects FM, not AM, CD changer or weatherband. I suspect a bad solder joint somewhere, but can't decide whether it is likely to be in the radio itself, or the Diversity antenna. Anyone had a similar problem?
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Arne
The BMWs are all gone, driving Porsche and Audi now.

PJK

While it is acting up remove the radio from the dash and disconnect the antenna cable. That is the larger black one. Take a piece of #20 wire about 30" long and strip one end. Insert it into the antenna socket. If the FM works, suspect the antenna system.

Phil

BRuckdeschel · Joined: 16 Aug 2001 Posts: 45 Location: Canfield, OH

Arne,

Have you figured it out yet? Mine started doing the same thing this summer with an aftermarket Alpine. This may help you in trouble shooting other areas besides internal to the radio.

Brian
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1992 325is - Conforti CAI, ANSA exhaust, Jim Conforti chip, BavAuto lowering springs, Bilsteins, 16" BMW sport double spoke wheels

88_325is · Joined: 25 Sep 2005 Posts: 105 Location: TX

Arne · Joined: 10 Jan 2003 Posts: 1454 Location: Oregon

No, haven't gotten around to looking at it yet - too busy playing with the 240Z. But I am leaning towards the antenna a little, as when it cuts out (abruptly, not fading) the stereo indication goes also. There are times when it's getting ready to go, that the signal gets extremely static-filled. So I'm pretty sure that the reception of the signal cuts out.

On the other hand, AM and weatherband reception is unaffected, it works perfectly at all times. So I'm not sure if there is a separate FM circuit in the Diversity antenna unit. If not, it pretty much has to be in the head unit itself.
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Arne
The BMWs are all gone, driving Porsche and Audi now.

PJK · Posted: Fri Nov 18, 2005 1:20 pm Post subject:

The AM antenna is seperate and it has its own amplifier in the box located in the driver's side rear pillar. The outputs of the AM amplifier and the FM amplifiers are combined in a diplexer before the output connector.

Phil

Arne · Joined: 10 Jan 2003 Posts: 1454 Location: Oregon

Been a long time since I've been here, but I thought I'd stop by to ask a question - since I now strongly believe that this issue is the antenna module in the rear near the window, anyone have any good recommendations where to find an affordable replacement unit? Used would be OK I guess, if I was pretty certain it was still good.
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Arne
The BMWs are all gone, driving Porsche and Audi now.

PJK · Posted: Wed Jan 24, 2007 7:21 pm Post subject:

Before you replace the antenna electronics I would suggest that you perform the simple test which I described.

It may be easier to perform the test if you use and adapter from the OEM antenna connecter to Motorola connector.

Phil

lesl2 · Joined: 27 Nov 2004 Posts: 499 Location: California

Hey Arne, welcome back. I had the same problem before. I cured it by spraying electrical contact cleaner on all the connectors/sockets to the antenna amplifier. If you need a used one. This place has them:
http://www.data.bmrparts.com/bmwparts/1316.html
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1997 M3 Auto Sedan
1999 M3 Manual Coupe
2002 530i Premium/Sport Package

Beemer3181s · Joined: 15 Jun 2003 Posts: 209 Location: UK

I've got a similar problem... My FM reception fades considerably when the rear screen demister is on. I'm guessing its because the rear screen heater matrix and the antenna are so close to each other on the rear screen.
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PJK · Posted: Wed Jan 31, 2007 1:39 pm Post subject:

In US cars and I would guess UK cars as well the screen heater and the FM antenna are more than just close, they are one and the same. In the boxes mounted in the roof pillar are diplexers to islolate the DC for the heater from the RF signal from the FM antenna. I would suspect a problem in the antenna boxes with the symptom you describe.

Arne · Joined: 10 Jan 2003 Posts: 1454 Location: Oregon

I stopped by the forum here to do some research as I prepare to sell my father's E30, and thought that I should perhaps close out this thread.

Yes, I still own my 328i, and I no longer have FM issues. The problem was not the antenna modules, but was the tuner in the factory head unit (the original Alpine C33 w/weather band). I diagnosed this by swapping in a different C33 from a co-worker's '97 328i. That worked perfectly, so I bought and installed a used C43, all is now fine.
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Arne
The BMWs are all gone, driving Porsche and Audi now.

PJK · Posted: Fri Apr 30, 2010 2:17 am Post subject:

You could have had this sorted out in Nov. 2005 had you followed my suggestion.

Phil