electrical drain from head unit

[Rev Run D]

Had a power drain in my car - battery lasts only 3 days before dying. Took it to the shop to diagnose - they found a drain from the head unit. How do I go about figuring where the drain might be coming from and fix it? electrical stuff ain't my thang.

[Vincenze]

Check it visually for burned parts.
If you connect it to +12V, then you can check with your fingers if any part is hot.

There are E30 headunits on eBay, Facebook marketplace. You can swap the components.

[Rev Run D]

to add: It's an aftermarket headunit, and everything seems to be working fine other than the drain.

[Vincenze]

You can buy a cheap multimeter, disconnect the - (negative) cable from the battery, turn the multimeter knob to 10A, and check the amperage between the - battery terminal and the - cable.

Then, you can remove the fuses one after another, and check which fuse is responsible for the drain.

Then, remove the headunit and check the amperage. The antenna can also be a problem.

[zwill23]

It sounds like someone just set up the head unit w/o switched power. Pull it out of the dash and check the wiring, even for someone who isn't electrically savvy it should be pretty simple to diagnose. Look up the head unit wiring diagram and compare the wiring to an E30 wiring diagram for either base or premium sound depending on what your car has.

You got this!

[Gregs///M]

Drains from the head unit, even aftermarket are extremely rare. Another much more common drain is the SI board inside the cluster which is on the same fuse as the radio. So its very possible the shop that did the troubleshooting mistakenly thought it was the HU, when it can be the SI board. Be sure your SI board is properly refurbished and it will get rid of this issue. Try disconnecting the cluster and watch the drain go away. Or if you remove the HU and the drain is still there, bet its the SI board.