UK Car Repair: renault laguna wont start, alternator belt, renault laguna

Question
QUESTION: hi guys hope you can help. i've just had mt alternator belt replaced on a renault laguna 1900 deisel on an x plate. now it wont start. it'll turn over but not fire up??? any toughts please. thank you.  kevin

ANSWER: If it turns over I doubt it is anything to do with the alternator, UNLESS something was inadvertantly disconnected so check all of the wiring. Does the car have any kind of glow plug indicator and is it functioning?

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QUESTION: thanks for responding so quick. the car is still at the garage so cant check. i was wondering if it was something to do with immobilising system?? is there a code to reset?
it snapped on the motorway. i lost the power steering but it still drove ok. it's a xje high spec talkind car. the first i knew was the voice saying hte battery wasn't being charged. so when i was  safe to do so i turned the engine off and tried to restart to no avail. RAC man said it should still start even without a belt but it wouldn't. he seemed baffled that's why i was wondering if it was something to do with immobilising system and whether there is a reset??   many thanks   kevin


Answer
If the battery dropped below 12 volts it would most likely trigger the security system. Try resetting with the regular key by locking then holding for a few seconds then unlocking and holding. Try it a couple of times, otherwise you need to access the on-board computer. why would the battery go dead so fast? and what caused the belt to break, was it just aged or was something putting an extra load on it?