i have a 2001 disco 2 and a few months ago something started draining the battery. I thought it might have been the aftermarket radio but its been disconnected for a while now to rule that out.

Is this a common issue with the d2? the radio was installed years ago with no problems, and then suddenly something just started draining the battery. We have tried multiple batteries as well.

 

Check your battery terminals and make certain they're getting a good connection. The alternator might test out fine, but if it can't properly keep the battery conditioned it'll lead to a short battery life/charge.

Use a meter and measure the voltage at the battery with the key off. Should be 12.5 or higher. Then with it running it shouldn't be lower than 13.2-13.4v, if it is your alternator isn't putting out enough output to keep the system topped off. I had a Valeo Alternator on an 04 only have 10.9 output and it never tripped the battery light.

 

another issue is if you had air suspension and it was converted to coils and then not turned off and the switches pulled could drain it by constantly running the pump