Parasitic Drain

I have a 01 1/2 ton in the shop that has a drain. No aftermarket equip is on it. Ive unplugged the light under the hood thinking it was it. THe drain is intermint. It has not acted up for a week until this morning.
N E help apprecitated.

audio amp sticking on?

bad alternator diode

bad alternator diode
That is what I'm thinking. I havent messed with it much yet, but i do have a good alt. for the truck that Im going to test.

THanks

USUALLY YOU can just disconect the battery lead on the alt..(the big wire)..then tap it back on the stud that you just removed it from and see if it sparks..it won't unless a diode is letting the power go back the wrong way

If you have not replaced the battery since owning the vehicle, I would suggested to replace the battery.

I've had a so called drain on one my vehicles. I've checked fuses/relays and they are all minimal. I've swapped out a same type new battery from my other vehicle and I don't have anymore drains and I can start my vehicle no problem. Knowing it was my battery, I've replaced it with a new one and I have no more problem. Old battery seems not able to recover from those small drains.

Anyway, to check for battery drains. I used a digital multimeter that can read milliamps. I disconnected the + terminal cable and attached my multi-meter between it and read my current battery drain and gradually remove fuses and note the difference and see which one is draining a lot.