E39 528I Amplifier vs radio issue

Hi everyone... just bought a '98 528I and the back subwoofer speakers are popping. No noise coming of them. The front speakers are in tweeter mode. I have read several threads regarding radio vs Amp. Still not getting it... I went ahead and replaced my cassette with a CD player. Still having the same issue.... so I know it's not the radio. I've taken out the back speaker and had them tested... ok. Is the amplifer the only thing left that is causing this?? Maybe a channel out?? Or do I have a wiring issue? This system is DSP.

Thanks for any help.

Hi,

you've started, so you need to continue the fault finding process. Check all fuses, undo, then re-attach all connections and make sure they're seated properly. Change to a known working DSP amplifier of exactly the same model number and revision as you have, test each speaker....

cheers, Dennis!

The DSP amp is a multichannel device, with separate outputs for the various speakers. Yours may be kaput, or there is a connector problem somewhere.

Carefully examine the output connector on the amp for dirt or corrosion.

I checked all the connections and they seem to be fine. (unplugged - cleaned, then replugged) Noise is still the same. I guess the next step is to find an amp to replace. I have pulled it out and read the model number. I've seen several of these on Ebay - but I've very careful of buying there. Any other spots to buy a 'known working' amp? Don't know... maybe I can take the amp to radio installers and they could possible test? Thanks for the info so far!

Hi,

No real way of testing a second hand amp until you plug it in to a car and check for yourself! I don't think any pro installers will have the rest of the setup of the OEM modules hooked up to a test bench to test modules out i'm afraid, so it's really down to you taking chances...

Cheers, Dennis!

Its either 1 of 3 problems (assuming your sub works fine as you state)
1. preamp input to amp from radio is bad: unlikely if other speakers are working
2. Bad amp. Very possible but to have just one channel bad is a little suspicious
3. Faulty connection from amp to subwoofer: Very possible
I would test the output at the actual amp. to make sure its not a simple as #3:
-Do a quick search for E39 Amp replace/install DIY to find a wiring schematic and tap into the + & - sub output with a different length of speaker wire, possibly connected to a test speaker. It would be best if you could fully disconect the amp to sub connection, as a crossed wire or ground somewhere could also be causing your problem. If you get sound from the sub output obviously your amp is fine, and you just need to run new wire/ make new connections.

Thanks for all of your suggestions. I have pulled the left rear c Pillar off to check the antenna amplifier. I have a e39 528I, do I have a second antenna amplifier? If so where is it - behind the right rear c pillar?? thanks