Battery drainage 1980 528i (resolved)

[Joe Boston]

I know there are many gremlins with the 528i. I just recently purchase this car that has been sitting for over 10 years. When I received the car it had a battery that didn't hold a charge, and just recently purchased a new battery.
I would start and drive the car almost every day and didn't realize I had a draw on the battery. But i went on vacation and came back after 10 day to find the battery dead. That's when I started to looking for items that can draw the battery. I have a new hazard switch, checked the rear lid and removed the bulb, did the same in the glove box. Charged the battery and again battery dead after 3 days.
After recharging the battery again and staring the vehicle the starter remained engaged after the car started. Immediately I turn the vehicle off, but the radio and digital clock still had power, along with he blinkers.
So i thought it would be the ignition switch. So I removed the lower panel to access the ignition switch plug and removed it from the block, and the radio and clock and blinkers still had power.. not until i turn the blinkers on that everything shut off. ( at this point very puzzling)
After searching this forum I couldn't find any similar gremlin..So i performed did the amp test and found that the pink relay in the photo


does anyone know what function this relay has? I went thru the wiring diagram and couldn't figure it out. Once i disconnected the relay the draw went down to less than 1 amp.
I have ordered a new ignition switch, in the mean time need to figure this draw ...
if anyone has any insight.
thanks
https://www.flickr.com/photos/147243459 ... ed-public/

[Lock]

On my '79, those two external to the fuse box relays are for the high and low speed operation of the radiator-mounted aux fan. I forget which is which, but simple circuit, one is triggered by the 90C temp sensor in the radiator and the AC compressor, and the other one runs from the 99C temp sensor. At least one is mounted on the radiator just by the compressor. I use that one as a radiator drain plug.
You can figure out which is which by running a wire across the contact pins (NOT the coil pins) of the relay socket. The fan will either run slowly or fast if it's working. Or maybe not at all.
But they shouldn't be energized when the battery is connected. You probably have a wiring short in the fan or AC circuit, or the temp sensor is faulty.

[Joe Boston]

after reviewing your post, I was able locate it on the wiring diagram.
stage I relay is connect to fan motor and then connect to Stage II relay.
I changed the relay (I believe the PO had replaced it with the wrong relay), and noticed the draw dropped drammaticlly.. Still need to change the ignition switch ..
thank you for the info

[Lock]

Good catch. Looking closely at your picture I notice that relay is for an Audi. I guess just because it fits, doesn't mean it's right!

[Joe Boston]

for anyone that is having the same kind of issues.
the battery drainage was due to a relay that was for the stage I of the aux fan for the a/c. PO had put the wrong relay, it was for a later car with ABS.
The other issue i was having, after shutting down the engine and turning the key in position 1 the radio and blinker along with wiper still had power. This was caused by a faulty (new) Hazard switch..

[T.Hanson]

Thank you for your posting the detailed information. I had a serious battery draw I traced to corroded alternator wires, enough to keep the multimeter happy for fast starts after two or three days between drives.
In the event the multimeter gets picky, shows less than the best new battery 13.2 (?) I appreciate the tutorial on the relays, with photos, things to check.
Looking at one wiring diagram can make me catatonic.