For a few years now, the 330d’s rear right speaker hasn’t been working. As I sit in the front, I chose not to let that bother me. However recently, both front and rear left speakers cut in and out a few times, and then stopped working altogether. This left the front right and the sub, which was enough to prompt me in to action. I know the screen at the front is a fairly dumb terminal, and that the audio gear is all in the boot:

I traced the problem to the item described above as “Radio/Car Amp”. It’s a Becker BM54, and a short trawl of the internet quickly revealed that the amplifier’s output stages are a fairly weak link. Replacement units seem to cost several hundred pounds. Hmm.

There were some eBay sellers willing to effect a repair for a couple of hundred quid, mentioning reflowing solder joints. While consulting various forums though I saw a recommendation that caught my eye. It seems that Cartronics, a firm based just a few miles up the road from me who did a decent job of installing a Thatcham approved immobiliser in my second E30 M3, offer a warrantied repair for similar money. They claimed their repair involved entirely replacing the amplifier’s output stages to both ensure this wouldn’t happen again and provide a superior sound. I concluded that while the £210 they were asking was a bit rich compared with the cost of a standard head unit, the sound quality certainly couldn’t get any worse, and they were at least a devil I knew.

I dropped the unit off late on Saturday, and they called lunchtime today (Tuesday) to say it was ready. I understand they also provide a service by mail. This evening I’ve verified the repair, and also concluded that the sound quality certainly isn’t any worse.

So, if your BMW (or Range Rover) speakers are cutting out, locate your amplifier module and get it sorted. While mine is a B54, it replaced the B24 which also suffered in a similar matter, and I noted Cartronics had a couple of those also in for repair at the same time. In e46-land, to remove the module, start by lifting up the boot floor:

Remove your rude-boy sub, tow hook and spare wheel cover. Then using a 10mm socket release the two black plastic nuts and open the flap to the comms deck. I found a 3/8 extension a useful prop to hold the flap up.

There’s a big black block connector that can be unclipped. Before going too much further though I’d trace that to the nearby (and just out of shot below) black connector and make sure all the pins in that are firmly home – I’ve lost sound before due to those working loose.

In the above picture I’ve got two unused white connectors. The lower left one is from the old CD changer – my rather primitive iPod kit actually replaces that in the black block connector. The loose white connector at the top by the TV module is the old A/V connector – my DVD player has replaced that. So, remove the black block connector, the aerial (on the left) and the 8mm nut, and whip out the unit.

Send it off to repair, and it should come back with one of these stuck on it.

Plug it in and off you chug down the road. Boom-tish, boom-tish, etc. :)