My ‘04 E60 was having some trouble. I am not sure if they are connected, but they did happened sequentially. It staerted the day before yesterday.

First of all the ac blower was giving off strange noise. It sounds like the motor bearing was giving out. The sound got worse if the blower speed was increased. When I looked through the center vent hole I can see water dripped very slow.

On my way home suddenly the very low coolant level warning came out, eventhough I just topped off expansion tank. So I decided to drive back home. The car drove back home without any incident.

At home I checked the coolant expansion tank and found that it was leaking. The day after I ordered a new tank and today I replaced the tank. No problem in that.

After I replaced the tank and refill the coolant fluid I wanted to turn on the engine to run engine on idle to circulate the coolant and see if I need ot add more coolant into the tank. When I wanted to start the engine I just relaized that all of the electricals are dead, and there is only the fan symbol in the blower setting dial that was on, and it was on with red glow.
I checked the battery and found that there’s only about 3,5V left in the battery.

My thought is that the blower motor might be shorted either to the bearing gave up and it overheated, or the water drip that I saw cause the motor to be shorted. Because the motor was shorted it drained the battery.

Could that be what happened, or could it be something else? How can you tell?

In this case where the battery is drained like this, is it wise to try to jump-start the car?

And then, when jump-starting the car, is it safe to connect the jumper cable directly into the battery in the trunk? I asked because my car was parked head-in first in my garage and there is no room to park the donor car next to it.

Need advice, please.