alright since none of the a-holes over at jeeps unlimited wanna help me i was hoping one of you friendly audi fans might give me some adviceeven though its not audi related. i got a grand cherokee laredo not to long ago and the previous owner said that the alarm would sometimes drain the battery... anyone have any ideas on what would cause this? thanks

 

Any type of short circuit in the alarm system could cause a battery drain. Unfortunately that kind of problem is a real pain to trace because all the wiring is built into the car's harnesses (I'm assuming we're talking about a factory alarm system here), and you were told that it could sometimes cause it. Intermittent electrical problems can be a real bear to track down (I'm an electrical engineer and do it for a living - believe me, it's a pain sometimes lol). Have you had this happen to you since you got the car, or is it just info passed along and you haven't yet seen it happen? If it hasn't happened to you yet, it's going to be almost impossible to track down. You could go to www.alldata.com and buy a year's subscription to the info on that particular car and use their troubleshooting flowcharts and information to try and trace the problem though - they've probably got resistance and voltage readings for the majority of the sensors on the car, and you may find one that's out of whack by taking some measurements and comparing them to the listed, expected values.

 

yeah it is the factory alarm system andno it hasnt happened to me yet but id rather figure out what it is before it does happen (if at all possible) im in an automotive elctronics class in school right now and have access to shops so hopefully i can bring it in one day when i get it up to ohio and we can figure it out. i just wanted to see if anyone here had any ideas so thanks man

 

anything is possible, but usually, an alarm will draw just a little bit of voltage when the car is armed. i will look up 'acceptable' voltage draw at work tomorrow, i think its like 10ma (which is on the high side) also, check stupid things like the glove box light, maybe the 'pin' isn't shutting off the light. same with door/ hatch lock assy's (providing that the switch is built into them) or maybe the battery is boaderline ( i have seem a few intermittant batery problems) electrical probs can be a PITA, good luck....oh yea, if it has a aftermarket radio thats 'hard wired' (so it can come on without the key) that will suck a battery dead in no time, like a few days. just a few thoughts........

 

I had the same problem in my Lincoln Towncar. I just put a killswitch on the battery

 

I agree with skills here but add the hood alarm switch which is also a common fail because its in the weather and rusts the contacts ( corroded contactswhen shorted toground become permanently live ) as you probably already know and that causes a large drain on the battery

 

alright thanks guys ill have to check some things out next weekend and maybe i can get a littlle more detail on what exactly is going on.