car cranks but 99% of time wont start
 

1986 FC base
ok, ive got an optima yellow top(750cca). the other day my alarm started randomly going off so i grabbed the keys real quick and disabled the alarm. i didnt think much of it and when i went to go to work the next morning it cranked for about 2 minutes collectively until i could hear the battery slowly winding down. now, it usually take a hot minute for it to start as it is but this is rediculous. if i hook another vehicle up to jump it, it for the most part will start up almost like normal. but i think i have something drawing power slowly off my battery while it sits. the optima is only about 3 months old, i dont have any crazy aux lighting. and to my knowledge all of my lights in the car are turned off. is there anyway to see if something is drawing power off my battery, cause its gotten to the point where i cant take it anywhere unless i take jumper cables and hope i can find someone willing to sit there for a few minutes to let their lil battery attempt to charge this damn optima lol. any info would help. thanks

Got a multimeter handy?

Shut all the doors and disconnect the positive batt terminal. Set meter to amps, and see what your current draw is.

On an FC, you should really never have more than 20ma parasitic draw when shut down and doors closed.

i actually do have a multimeter somewhere. do i just touch the multimeter to the positive terminal ( i have one ive just really never needed to use it......dont judge me)

Undo the positive terminal and connect the meter in series between the positive batt terminal and the positive batt cable.

You always have to have the meter in a series circuit to test current.

Disconnect pos. battery cable, put one lead from the multimeter on the battery terminal and the other on the end of the cable...you're bridging with the multimeter.

ah...makes sense now. i get off work at 3 or so so ill definetly try that when i get off work and let you guys know what the result was. thanks for the help