Recently, my car battery began to experience a significant electric drain. The battery could be in the 12.5V range when I parked the car, but it would be around 9.5V the next day. Fortunately, I keep extremely good care of my car, so it was actually able to start with that little bit of power (I was impressed!).
Of course, I didn’t want to ignore the drain at that point. I ordered a solar panel, thinking that I could wire it in, and it would keep the battery charged after I had taken care of the drain (so I wouldn’t even have to drive it every week or two, if I didn’t want to). I hooked up the adapter near the driver’s side kick panel, which was quite easy. Then, onto the hard part: dealing with the drain.
My turbo timer was acting up (it would work, but the screen sometimes didn’t turn on), so I removed it and also rerouted the boost controller. I took that opportunity to check for any obvious problems. I suspected that one of my butt connectors might have come off, but I found that every single addition/change to the wiring that I have done in my car was still good. That meant I needed a more methodical approach.
My next bet was that a relay was stuck shorted, so I pulled every relay in the car and checked each one. The “flasher” relay is going bad, but it’s not the source of the electric drain (I did order a replacement for it anyway). Without any obvious signs, I decided I would remove every fuse, checking the circuits one by one and leaving all fuses out. I came across the high current fuses and made one mistake: I assumed that they all pulled out just like every other fuse. Wrong! Two of the five are screwed in.
The picture shows the “sub box” that holds these fuses. I had to remove this box from the main fuse box to get to the screws. Well, I guess I should point out that I didn’t do this the first time. I pulled on one of these two fuses and it came out, but the metal broke inside the little plastic box, and it left the two leads behind. The other one actually shattered in my hand. Most of the pieces flew all over the place, but a nice chunk went into my thumb. I pulled it out quickly and went back to work, moving some relays to make room for the fuses.
When the relays start to feel sticky, I noticed that my thumb was bleeding quite a bit. Oops. I took a break for the day, and my buddy Eric played taxi the next day, so I could pick up some fuse replacements. I pulled the extra high current section of the fuse box out and removed the screws to pull out the remaining leads from the two fuses I broke and replace them with the new ones.
Long story short, I’ve found out that the ECU-B circuit is using as much power as all other electronics in the car put together. Unfortunately, that circuit supplies power to both the air bag and ABS, two things I’d rather not mess with, so I put it off until tomorrow. I disconnected the ECU-B fuse and connected the solar panel. I could actually “see” it trickle-charging the batter via my multimeter, which was a good sign. We’ll see how tomorrow goes….
Ian,
Please be careful with all this. I know that you are but still… things happen.
When I was very small, I once was showered with gasoline. I was standing under a very large storage tank. They were not expecting gas to come out when they made some change. But gas came out, lots of gas came out, and I was right under it.
When I was older (maybe about twelve), I grabbed a live wire and got a severe shock.
Well, I lived through several things. Maybe they are responsible for my brain’s not doing things the way “ordinary” folk do.
Robert
Yeah, I only checked a few things today. I’m at the point of becoming frustrated. It could be the ABS ECU (which is under the dash), something in the air bag system, or some random thing that doesn’t make sense at this point. I really don’t want to mess with the air bag ECU or any of part of that system, but it’s looking more and more like I’ll have to. I’ve already managed to store an air bag fault code in the ECU that is a serious pain to clear. I tried without success for half an hour. I think I’ll wait until I have everything else figured out before trying again. Otherwise I’ll probably end up setting off the code again.
It sounds like you’ve been through some crazy things. I figure every experience makes us who we are, good and bad. Besides, ordinary isn’t as fun.
Hi Ian!
Just wanted to give you some feedback:
1) I’m really happy I found your blog! It has the right amount of geekyness to interest me, but simple enough for me to understand. It has saved my brain from melting due to boredom.
2) It seems you have isolated the drain to that one circuit? I apologize if I misunderstand, but at least on my car (Mitsu Galant) that circuit is 80A, and way too large to cause slight decrease in voltage overnight. It would dry the battery out in less than an hour.
I had the same problem as you. I went over the small fuses with an amperemeter to see which ones were closed circuits, and found that the only one was the aftermarket alarm/central locking. Replacing the controller board fixed the problem.
And, one more thing: Be careful with the airbags. Those things don’t inflate. They blow up. As in detonate.
1) Thanks! I try to mix in a variety of things, so that I’m not too heavy in one direction (too geeky, crazy art guy, etc.). It seems that a lot of people prefer blogs on a single topic though.
2) Well, I isolated the primary drain to one circuit. I noticed today that the battery was pretty weak after 2-3 days since I last drove it (and I left that fuse disconnected after I parked the car, so that circuit didn’t do it). I’m starting to think I ought to have the battery tested even though it is less than a year old. Of course, it also snowed four inches last night, so that doesn’t help with battery power.
Where did you get the 80A figure? If you’re just reading the fuse, that’s the current that it will (or should) burn up at. The circuit itself should never draw anywhere near that much. While a car is off, most will only pull X milliamps. The exact amount depends on the car (an old car just keeps the clock and radio supplied with power, so it will draw 10-20 mA; newer cars often have computers that keep supplied with power and can draw ten times that). If the circuit were pulling that much power, the battery would probably be unable to start the car within an hour, and possibly too dead to even charge by the next day! As far as when the car is running, I would still suspect that circuit to draw much less than 80 amps. In fact, the alternator in my car only generates 100amps (and many produce less), so if a single circuit drew 80% of the power, there’d be trouble! Usually a fuse rated much higher than the normal current draw is used because many systems draw a lot more power when initially started/connected before balancing out (due to capacitors and other components).
My immediate thought with the drain was that it would be something aftermarket (radio, amp, boost controller, etc.), but nothing I have added is connected to the circuit that is causing the big drain. It’s interesting that you mention the alarm though because I hadn’t really thought about that. I’ll have to check to see which circuit(s) the people who installed it connected it to… as soon as the snow goes away, haha. Thanks for the idea!
Yeah, I haven’t wanted the airbag to shoot my head through the back window or t-tops, leaving my body behind, so I’ve avoided really messing with it at this point. I have the “Big Green Book” (repair manual), which has all the “correct” procedures and circuit diagrams, so I’ll definitely be following that word-by-word or diagram-by-diagram if I end up having to deal with the airbag. It’s certainly going to be at the bottom of my list of things to check though!