The battery in my FD drains over night after charging so that I can't even start the car. I purchased a multimeter to find out what's causing the parasitic draw. I don't know the age of the battery, which is a Optima Yellowtop. The battery has discharged a few times because I forgot to turn off my boost controller.

The instruction manual that came with the multimeter instructs me to switch the multimeter dial to the "10A (or 200 mA)" position. When I test the current draw, the display shows 0.20. Is that too much power being drawn with all accessories off?

I pulled all the fuses and found that my GReddy Profec-B and Defi Gauge ECU is drawing about 0.8 together and the 10A "Room" fuse (according the Mazda Service Manual includes the dome lights, ECU, etc.) is drawing about 0.1. When both fuses are pulled, I get about 0.02 current draw.

Is 0.20 high? I google'd looking for some tutorial to understand the numbers but I can't figure it out. How much is 0.20 when the dial on the multimeter is at 10A? I'm assuming the display is showing Amps, so .20 is 200mA, which isn't very much is it since the manual says typical current draw is about 100mA. Or am I reading the display incorrectly and the draw is excessive?

Maybe my battery is just bad?

 

Can't really help you with your multimeter question, but as far as your boost controller goes, did you hook it up to the battery directly? why didn't you hook it up to something that turns off when the car turns off? Might save your future battery if this one can't be salvaged

 

If you tell me the meter you have or show me a pic I can help you out but I dont even know what your trying to read. But read for voltage and see what you get if your reading voltage there then you have an issue. And if all else fails pull the fuse and ground out that side of the fuse holder and read the wires for Ohms if you have more than .1 then you wire is bad.

 

i had the same proble, i ended up taking apart the inside of the car. i found about 10 or so wires that were grounded that were cut and didnt lead to anywhere. after i got it all cleaned up i never had a battery problem again.

 

The boost controller is hooked up to a fuse on the fuse block next to the clutch pedal. The boost controller has a on/off button, so I normally turn it off when I leave the car. I guess I should try to attach it to an accessory line.

 

This is the multimeter I purchased:

http://www.actron.com/product_detail.php?pid=16156

I'll take some pics when I get home.

 

Yes! A question that I can answer! Considering I can't seem to grasp the rest of the mechanics... I can understand a piston car and I have worked on piston cars all the time.. this rotary.. the vacuum and the scare of broken seals just frighten me..


But to answer your problem,

You have too much of an amp draw. Ideally you want a .02 Amp draw
You have a short in your dome light circuit somewhere. It should not be drawing .1 of a amp.

Your greddy profec B and defi gauge either have a poor ground and they are staying on 24/7 They should shut off after awhile. especially your defi gauge. that doesn't need to store any memory in it with a 12volt contant.

You should re check those.

Your yellow top shouldn't have a problem, however I had three yellow tops ruined in my Eclipse tsi because I kept storing it over the winter leaving the battery on and not firing it up at all.

Jack

 

OK, i unplugged the boost controller and the draw dropped down to .08. The reason the "room" light was showing .1 was because the key light was lit. It turns off 10 seconds after closing the door. With the Defi ECU and Boost controller unplugged, the draw is only .02.

So, I drove my car around for about an hour and then turned it off. I immediately tried to restart it but it wouldn't start. Battery voltage was about 10.6v. I guess now I have to test to see my alternator is bad? The car runs fine and my Power FC commander shows 13.7-13.9v when the car is running, so I'm assuming the alternator works fine. Does this mean my battery is just bad?

 

Take your battery in to any auto parts store and they can load test your battery. You're alternator is fine if you see 13.7 - 13.9 V on the PFC.

 

I am a mechanic-15years. First thing you want to do is charge the battery up on a trickle charger and do a battery load test and alternator output test. You are going to need a shop tool- Vat40, vat60, or take it to pep boys etc. If those check out then, read this-

The max draw on most cars is .050A- thats 50milliamps. Some newer cars that have many control modules allow up to .080A+. To properly check for a draw you have to turn all consumers off of course, disconnect the negative terminal on the battery and run your meter from the negatvie cable to the negative post. Make sure the black/ground lead on your meter is in the black/- spot on the meter and the red/+ is in the amp/A spot- not the ohm or voltmeter spot or you will blow the fuse in the meter. After hooking this up wait at least 15minutes to for the control modules to fall asleep. I work for Mercedes and most of our new cars take upwards of 30 minutes for the control modules to fall asleep. But older cars you can check right away. .080 is 80 milliamps and .80 is 800 milliamps, 1000mA= 1 amp. Usually computers and modules when bad draw around 100-300ma and usually anything over that like 600ma is an interior light. First check for obvious things staying on, dome lamps, interior lights-glovebox lights etc. If no obvious things are found then- Best way to isolate a draw is to pull fuses one at a time and watch the meter. If the meter reading drops right after you pull a fuse then check whats on that circuit and put the fuse back in and unplug what was on that circuit. BE careful many fuses will have several consumers on one fuse. Note: a draw of .100-.200A would take several days of the car sitting to drain a battery down on a good battery. So check the battery and charging system first and go from there. Good luck.

 

Not always. You can have an alternator that puts out good voltage but not enough amperage, so to properly test this you would need a load test tool. But 9times out of 10 you can get by with just a voltmeter test. Its that one time that will bite you in the **** though.

 

There is a spare outlet right there that switches with the ignition.

 

I replaced the battery and everything is fine now. I didn't think it was the alternator since my car only has 37k original miles and the problem started after letting the car sit for weeks. The Power FC now shows the 14.4v when the car is on, as opposed to the 13.6-13.7 I was seeing with the old battery.

I figured it was most likely the battery since I've let it accidently discharge several times over the months by leaving the boost controller on. I also let my car sit for 3-4 weeks at a time without starting it up at all. Also, the yellow top had a manufacturing sticker of 10/06, so it was less than 2 years old. Optima Yellow Tops are supposed to last much longer than 1.5 years. I had to put down $200 for a new one. I guess I'll be more vigilent and make sure no accessories are on or disconnect my battery when I let my car sit for extended periods of time.

 

For future reference, draining your lead-acid battery down shortens its life. Lead-acid batts don't like to be deeply discharged. Anyone that starts to notice battery/starting problems should find the problem asap to save heavy wear on their battery. It is also a good idea to keep car batteries fully charged when storing them long term - use a trickle charger every few months while storing.

 

would an aftermarket alarm cause more draw?

 

Most car alarms draw a very small amount of power (to monitor its sensors), but usually not enough to hurt the car battery. The battery should survive months with a car alarm armed. Even if you have to leave your car parked a long time w/ the alarm armed, risk of completely discharging your battery once is probably worth the alarm protection. Otherwise I would disconnect (or remove) my battery for long term storage. Hope that helps.