Hi, the vehicle in question is a Disco '98 TDi 300 auto.

The problem is that the door mounted sub woofer and amplifier is not working at all.

Checked that it's wired up - it is as far as I can see.

Checked every fuse on the car, no problems found.

It has a radio cassette head unit but no CD changer.

Anyone got any ideas please?

Cheers
Dave[/align]

 

I am asuming that you are using an aftermarket deck? If so you will have to do an amp integration, which is basically just a special wiring harness, in order to get power to the sub and amp. Check to make sure that you have the REM output from you deck pluged into the factory amp's REM input. The REM is the wire that tells the amp to turn on with the deck, and its usually a blue wire with a white stripe. If you have done all this then the next step is to use atest light to make sure you have power to the rem wire from your deck and also to the amp.If you had power there, then nextcheck for power from the amp to the speakers. One of the two spots that I have told you to check is bad. It will either be a bad connection at the wiring harness or a bad amp. BUT if you have power to everything I have listed above then you may have a bad subwoofer, some amps have sensors built in that won't let power to the sub if it is blown or bad.So if there is power to the sub then the sub is bad. If this doesn't help you please let me know and I will be happy to go into more technical detail to pinpoint your problem as best I can! If by chance you are using an aftermarket deck and wiring harnes make sure that the two REM wires from the new harness are twisted together as one wire, then wire it in as normal. So it would be all 4 wires together as one. If you don't do this you won't get a complete circuit.

 

If by chance you are using the factory deck then you need to test for power from your deck to the amp and for power from your amp to your subwoofer. If there is power to the amp but none leaving it then your amp is bad or has a bad fuse on it. If the amp has power to it and from it then your subwoofer is bad. Basically to shorten it up just check that all connections that should have power, have it. A bad connection is allways something to check for first when troubleshooting, just use a simple testing light!