Filling the Coolant = Total Electrical System Freak-Out
It’s cold outside. Really cold. So imagine my annoyance that the heat in my BMW Wagen was not working well. It was barely putting any heat out.
So I Googled for some hints. There were two main possibilities returned:
- The cooling system has air in it.
- The auxiliary coolant pump is bad. Because of course there is a second, electric water pump.
Since I had drained the cooling system a while ago and apparently did not fill the system in the proper BMW way I was guessing that #1 was the correct answer, but they are both easy to check.
So yesterday afternoon I decided to take a look. I popped the hood and looked in the overflow tank. It was empty, so #1 seemed even more likely. So I filled the system up the correct way, which is as follows:
- Remove cap from overflow tank.
- Remove bleed screw from overflow tank.
- Remove bleed screw from coolant pipe by fan.
- Turn on ignition, but don’t start the car.
- Set the heat controls to 90 degrees.
- Turn on the heating fan to the lowest position. (This turns on the aux coolant pump – which I could hear promptly start running, so that proved that the problem was not #2.)
- Pour coolant into the overflow tank until it runs out of the coolant pipe bleed screw.
- Replace coolant pipe bleed screw.
- Pour coolant into the overflow tank until it runs out of the tank bleed screw.
- Replace overflow tank bleed screw.
- Fill overflow tank the rest of the way.
All went well and I added about half a gallon of coolant to the system. But that was all the coolant I had on hand, and the overflow tank wasn’t quite full. So I closed up the car and the garage and decided to drive to the parts store to get more coolant.
When I started the car, several lights were flashing on the dash in a syncopated rhythm: Battery, ABS, Brake, Traction Control. Weird.
I let the car warm up a minute, hoping that the lights would settle down, but no such luck. So I turned off the car and waited a minute, since I’ve had to “reset” the car in the past.
When I started it again, it was doing the same thing. That’s weird, how could adding coolant cause the electrical system to freak out?
I figured that maybe having the ignition on for about 5 minutes with the coolant pump running had drained the battery a bit, so maybe driving it to the parts store will charge it back up. I’d seen the dashboard lights do weird things before, so I figured maybe that would fix it.
So I headed on over to the store. This was my fatal mistake.
When the dashboard on your BMW is lit up and flashing like a demented Christmas tree you should pay attention because it’s trying to tell you something.
Driving to the store I realized that not only were the dash board lights putting on a pretty disco show but the fan for the heating system was cycling on and off. That’s weird.
Traffic was pretty bad and I was not moving at all when all of a sudden the headlights started turning off and back on. The dashboard illumination was also flashing on and off. I felt like I was at a rave! But I was also getting concerned that the car was going to die in the middle of traffic.
As soon as I could I turned the corner onto a side street and decided that maybe I should head home. But the car was really doing a disco number and the headlights were turning on and off in shorter intervals so I pulled into the Burger King parking lot and shut the car off. I figured I’d give it a few minutes to “reset” and then try and drive it home.
When I tried to start the car again it said “Un-uh, click”. Dead battery. Whee. Well, that explains some of the issue. But the fact that the car was freaking out when it was running? That sounds like a bad alternator. Damn it.
So I called Stefanie and asked for a rescue. She said sure, be there in a few minutes. Then she called me back and said “There are no Subarus here.” I knew Liz had one, and I guess Roz went somewhere and took the other one.
So I called Roz and asked for a rescue. She was done with her errands, so she came and got me. When we got home Liz was arriving, so we ate some dinner and I collected some tools and Liz and I went to see what we could see about the BMW.
The first thing was to investigate the battery. The battery is in the rear right corner of the car, so I had to pull the rear deck and undo the sub-woofer to swing it out of the way.
I put the multimeter on the battery: 10.56 volts. Well there’s your problem. Still didn’t explain why the alternator wasn’t powering the car anyway, but it’s a start. So I hooked up the jumper cables from the Subaru and had Liz run the revs up to around 1200 RPM.
I checked the battery voltage again: 13.75 volts. So the Subaru is charging it, that’s good. I let that run for about 5 minutes and then tried to start the BMW. It fired right up, no lights on the dash or anything. It was like nothing was wrong. Well, great.
I unhooked the jumper cables and then checked the voltage at the battery again: 14.43 volts. So I guess the alternator is working fine then. Great. Awesome. Put the car back together.
I drove the BMW home while Liz followed me. No issues, ran fine. Heat even worked. Hurray!
This morning I went out to drive the BMW to work. I got in and turned the key. “Un-uh. Un-uh. Click.” Dead battery. Not really a surprise there. I know that the battery has been deep cycled at least once or twice since we bought the car, and I have no idea about before that. So I drove a Subaru to work and will be picking up a battery and some more coolant on the way home.
So why was the car freaking out before?
Best guess I can come up with is that the battery voltage was low enough that even though it started the car, something in the computer system decided that the charging system wasn’t working and thus prevented the alternator from putting out any charge. I dunno.
BMWs man, they are weird.