I have a 1999 Discovery Td5 Series II and a few days ago the immobiliser (or at least I'm guessing that is the cause) seems to have developed an "issue", i.e. the doors open via the remote fob (2 button version) as normal, the immibiliser light on dash stops flashing, all ignition lights as...

Thanks slob, will give it a try - have also read somewhere on www that it could be that thermostat is stuck (open)?

I'm a complete novice but would appreciate some guidance. Internal heating on my Disco Td5 seems to fluctuate? Left it on max heat, but after few minutes starts to blow cool air, then back to really warm for a while? Engine temp seems to remain normal, although fan seems to remain on for longer...