I know there's loads of threads on here about immobiliser problems and its not that I haven't bothered looking but the symptoms of mine are a bit puzzling....

Ok the car's a 1996 W210 300 diesel.

Went to the car for the first time in a while today, put a good high battery in, closed the doors, pressed the button on the keyfob to lock the doors - it did, putting on the flashing red light in the mirror. Then I pressed the button again and it opened the doors, putting on one green light in the mirror. Got in and put the key in the ignition turned it to position 3 to heat the glow plugs and then it put both red and green lights on together (flashing alternately) and also put all the indicators (hazards) on. The engine turned for ages but it just wouldn't fire. Tried doing all sorts of things with the keyfob for about 10 mins to no avail - refused to fire up (definitely immobilised). Then the hazard lights stopped flashing, I locked the door with the fob and the red and green lights both started flashing simultaneously, opened them again (lights still flashing), turned the key (lights still flashing) and I tried to start the car but this time it was trying to fire, which it did eventually after turning for about 20 seconds. Let it run for a few minutes, switched it off and immediately turned the key again and it started!

Left the car for about 5 mins, came back and it wouldn't start again aaaargh! I've tried everything for about 2 hours now. Disconnect battery for 10 secs and all sorts of time intervals, messing with the keyfob etc etc and it does the same thing every time.....once battery re-connected it will flash red light only when locking, put the hazards all on, green light only when opening, when you turn the key to on position the green and red lights flash alternately. Then eventually after a few mins the hazards will stop and then no matter what you do its green and red flashing together all the time.

I'm at my wit's end....what annoying me the most is that it did start once and never again after that - at least if it had never fired it wouldn't be as mystifying.

Sorry about the long read but I thought it best to explain everything in detail!!

Can anyone help???

 

i cant tell you much, but the lights flashing red and green on the mirror mean the remote batteries are weak. usually. in your case maybe not.
dont know about the lights flashing on the IR sensor on the door. how long was the car sitting...it is a diesel maybe you got gummed up?

sounds like an alarm issue maybe?