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08-03-2010, 10:11 PM | #1 |
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Problems finding battery draw
So my battery is dying if I let my car sit more than a day. I'm trying to use a multimeter to determine where my draw is by hooking up leads in series on the positive side of the battery (have tried the negative too). Meter reads .16 milliamps. I have tried removing all of the fuses with no change in amperage so I know I am doing something wrong.
Seems like all the how to's show the cars electronics are running fine with current routed through a multimeter, but when I hook it up no accessories or lights work, even the door open light goes out. I have spun the dial on the multimeter trying all the other settings to see if I am on the wrong one, but I'm pretty sure I'm on the right setting. Battery is a month old, and when the car is running there is a rise in voltage between battery leads leading me to assume the alternator is charging ok. What am I doing wrong?
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08-03-2010, 10:27 PM | #2 |
Trust no one
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Most multimeters with a current range have a separate jack for the positive lead to measure current. Have you moved it to that jack or is it still in the volt/ohms jack?
Also once you get it working, to avoid drawing too much current for the meter to handle this test should only be done with the doors closed, key out and everything turned off. |
08-03-2010, 10:40 PM | #3 |
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What is the charging rate with load on it?
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08-04-2010, 12:04 AM | #4 | |
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Quote:
Here is the multimeter I am using: http://www.oreillyauto.com/site/c/de...ord=multimeter I have the positive lead in the right jack that has the mA logo on it. It looks like this one has two negative jacks, one fused, one not fused. But I am definitely no expert. Should the door open indicator or dome light work when the multimeter is hooked up correctly? I'll have to check the charging voltage again and post up, I read somewhere that the alternator would have a diode problem and be draining the battery. This is on an 06 STi motor BTW. |
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08-04-2010, 01:28 AM | #5 |
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So far it sounds like you are testing it alright.
Now, even with a failing diode on the alternator, it doesn't explain why it would take a whole day to have a dead battery. Especially since you are only seeing a 0.12 mA draw (which is quite low by the way). So far I think it may be the battery. Drive for a while until your battery is charged up (a 2 hour trip should be sufficient). Then turn off your car and turn on your headlamps for about 3 min to remove a surface charge on your battery. Turn off your lights and test the voltage on your battery. For a good battery, it should be between >12.7 to 12.5 volts. Anything lower than 12.2 volts means your battery will be going out soon. |
08-04-2010, 08:33 AM | #6 | |
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Quote:
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08-04-2010, 09:02 AM | #7 |
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No that's not normal. A properly connected and functioning ammeter has extremely low resistance between the leads and should not significantly affect the circuit being tested. There should be a fuse for the ma scale, check to see if that is blown. If something tried to draw too much current through the battery while the meter was connected it may have popped the fuse. Usually the high-current (10A) range will be unfused, you can try that to see if the meter itself is the issue. And as I stated be sure to have the doors closed and key out when doing this test.
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08-04-2010, 09:57 AM | #8 | |
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Quote:
So I started out with a cheap Radio Shack multimeter, which did blow the fuse inside evertime I hooked it up and switched the channel to mA (after this none of the channels on it funcitoned), but the new multimeter I got, does not seem to be blowing a fuse because all of the functions still work after being hooked up. I think I tried the high current range as well, but can't remember. I'll try again today and post up. |
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08-04-2010, 11:31 AM | #9 |
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When you start looking for a current drain problem you would be wise to place the red probe into the left side 10A position since you don't know how much current is being drawn. When using that function you need to place the dial selection to the yellow 10A position. This could save you from blowing fuses in the meter. Most meters will only allow 2 amps to be measured in the normal right side position and vehicle systems can easily go higher than that if you happen to leave something on by mistake. In either current position the meter is basically like adding piece of wire in series with the power lead if things are working correctly so very little voltage will be dropped across the meter and most applies to the load.
Normal current draw should be around 15 to 25 milliamps when systems are in the sleep mode. Here is a link for you to check out that may be of help to you. http://www.aa1car.com/library/battery_runs_down.htm Having a good meter to make tests with is a great thing to have in your toolbox. You will wonder how you ever got by without it. A simple test light probe is another great thing to have also. Good choice on the meter from Equus. Last edited by Cougar4; 08-04-2010 at 11:37 AM. |
08-04-2010, 01:19 PM | #10 | ||||
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-------------------------------------------------------------------------- -Set your multimeter up for testing current (at least 10 amps). My multimeter can test 10amps continuously and 20amps for no more than 10 seconds. -Unhook your negative terminal on your car. -Clip the neg probe of your multimeter to the neg terminal. DO NOT touch the positive probe to anything yet. -Test the amperage quickly by touching your pos probe to neg battery post to complete the circuit (if it is over 10 amps swiftly back your probe off). Note the amperage. -You'll now start systematically test the amperage with pulled fuse(s) from your fuse box. Start with fuses that are greater than the amperage that is being drawn. (eg if you saw 12.33 amps pull the 15, 20, 25 30 amp fuses and skip the 2.5 and 5 amp fuses). Pull the smaller fuses last, in case there is more than 1 offending area of the electrical system. -Pull your first fuse, test by probing the neg post, back probe off post, pull next fuse, repeat test. -Once you find a pulled fuse that drops the current, then that is at least one of the trouble areas that is causing your draw. *if the initial test for current draw is less than 10 amps and your multimeter is fused for 10 amps, then you can just hook up your other probe to the neg post and test by pulling fuses. |
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08-04-2010, 02:21 PM | #11 |
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Dudes.
Awesome info. I'll be checking all this out after work. Also, cougar: I need to put the positive probe in the 10A position? |
08-04-2010, 04:09 PM | #12 |
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08-04-2010, 11:19 PM | #13 |
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Found it! Thanks to everyone's advice. Hooked up multimeter on 10A lead, current was between .534-.520A. Started pulling fuses in main box. Third fuse (defroster) removed and it went down to .014A.
I recently did a total STi swap into my 02 wrx wiring and all, and ever since my wipers, radio, and compass would run with keys out of ignition. Removing this fuse solved this issue also. Also, I swapped to auto HVAC and the defroster light does not turn on when the button is pushed(I know light works from doing HVAC diagnosis mode), but I can hear the relay under the dash. Could a bad switch be causing all of this? |
08-05-2010, 01:57 AM | #14 |
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Glad you found the problem. Now its time to solve the problem.
Now 500mA seems a bit too low for defrosters to run, so your defrosters aren't really on per se. In fact, what I find strange is that the Radio Shack multimeter blew a fuse from a current less than 1amp. Something else is going on here. I can't really tell you where to go from here since many things could have happened during the swap. If it were me I'd trace the wire but maybe others will have a better insight on the matter. Does the defroster come on at all? With the fuse in, can the defrosters be turned on while the car is on and/or off? Sounds like the electrical is a bit of a mess. Just to let you know, the electrical components tied to that fuse may not be the only source of the problem. Since the electrical was worked on, there may be other sources of the problem. If you don't mind the tedium, try test pulling other fuses while you leave the defroster fuse in. |
08-05-2010, 10:19 AM | #15 |
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As far as I know, the defroster has not worked since I did the swap and will not turn on at all (I can hear relay when I push button, but light does not turn on). There are only two wires going to the defroster, and they are hooked up right. I'm beginning to think that this is related to having a bad ac control module. I've been having ac issues as well (and I have double checked every wire associated with the ac for correct routing and continuity). There was no "custom" wiring, I followed the FSM exactly.
Edit: The radio shack multimeter had two channels to measure mA, 25 and 250. Reading the back of the multimeter, says the fuse is only rated to 315mA. Last edited by BMXspears; 08-05-2010 at 10:26 AM. |
08-05-2010, 11:20 AM | #16 |
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LOL, that is one crappy multimeter.
Alright, things are making more sense now. - ~500mA parasitic draw - Defroster fuse tied to problem - Defroster has not functioned since swap - Relay clicks when switch is depressed For some reason, your defroster switch is not tied to the ACC or ON key position (500mA parasitic draw). At 500mA you might have one or more mini backlight illumination bulbs on. Go test the relay. Make sure that when you pass 12v through the trigger that the power supply prongs have continuity...but also check that there is NO continuity when no 12v trigger is present. Check the defroster relay socket. See if the power source sockets have 12v when the car is ON (but not running). I'll assume you know how to check for this. If the power source shows 12v, jumper this to the socket that leads to the defroster, be careful not to tie it to the ground socket of the trigger, this will blow a fuse. See if the defrosters are on (glass should warm up). This should keep you busy for a bit. Henry |
08-05-2010, 12:43 PM | #17 | |
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Quote:
first issue is, and idea which relay is the defogger relay? Is this one of the relays on the back of the fuse box? I'm pretty sure it is not one the the relays in the block on the side. |
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08-05-2010, 01:01 PM | #18 | |
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Quote:
I'd just opt out and find another switch to test or just buy a new one (if it IS a relay/timer module). Good luck! |
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08-05-2010, 01:20 PM | #19 | |
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Quote:
Here's a link to the schematic I see 3 relays in this schematic... Last edited by Mulder; 08-05-2010 at 03:04 PM. Reason: link to copyrighted content removed |
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08-05-2010, 03:05 PM | #20 |
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Sorry we don't permit linking to sites where the manuals are posted, as they are copyrighted by Subaru and any public distribution is unauthorized.
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08-05-2010, 05:19 PM | #21 |
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08-05-2010, 05:26 PM | #22 |
Trust no one
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There is only one relay, in the under-dash fuse/relay box. It is controlled through the switch and the integrated module.
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08-05-2010, 07:21 PM | #23 |
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If the relay is under the dash and you still can't find it try to locate it by sound first [you mentioned you hear the relay click]. Then narrow it down by feeling the click of the relay switch jumping. Confirm it by using the multimeter.
You can feel free to test the relay and its respective socket. Before getting under there, find the wire right before it goes to your defroster. Use your multimeter and probe the wire or the harness closest to it and see if voltage is sent through when the switch is turned on. Just note it for future reference. Report back with findings. |
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