Golf MK4 immobiliser issues

[hannah363]

Hi guys i have a weird issue with my golf, i noticed that if i left the car running and say radio on it died after 10mins and had to get a jump start? i put it down to too much left running on my car , then i noticed that if i leave keys in not turned on but just so radio comes on it takes 5 mins and dies, it also does this if my iphone charger is pluged in, the other day i was out of the car for 15 mins left lights on! duh and car was dead when i came back! Brand new bosh battery new satrer moter last september, had battery and alternator checked this week and cant find anything, the only thing i can now think is that it may be the immoboliser as i have had issues with front and back drivers side doors and it only opens three doors from passengers side, i also have a black box fitted which is around the time things went on the car, proberly just coinsidence ? if it is the immobiliser guys i haveno idea at all, give me nuts and bolts but not electric any help as always is greatly appreciated. thanks