troubleshooting battery drain question

[57larry]

got a slow battery drain on a 2002 Saturn. if I disconnect a battery cable and use a test light in between to start pulling fuses to find the drain is how I troubleshoot an older car.  reading a wiring book by painless, it's stated to pull the radio and computer circuits to stop any draw from the memory section.

What fuses are in  the computer circuit? thanks

[rooster]

What fuses are in  the computer circuit? thanks

Maybe look on your fuse cover for a fuse layout diagram!

On the test light it should only be dim to hold the memory! Maybe connect a amp meter to see how much draw your getting. Make sure doors are closed and hood light disconnected when doing this.

You could run jumper wires, from your battery to the test light where you can see the light while pulling fuse's.

Any obd codes?

[57larry]

no codes

[wayne petty]

96 and newer OBD2 cars require parasitic draw testing be done slightly differently..

using a digital volt meter...

like this...



this is a battery cut off switch.. they are available for side terminal batteries also.. this can be rigged up to mount on a side terminal battery with a 3/8 bolt and washer.. and a longer 5/16 bolt thru the end of the battery cable to attach it to the end of the switch...


install your digital volt meter leads onto either side of this switch... the digital volt meter set to 15 or 20 amp scale.. and the wires in the proper ports in the meter.

with the switch connected...

start the engine ... let it run for a few minutes..  roll the drivers window down..   look at your watch.. note the time.. shut off the engine.. get out and lock the door in the same fashion you normally do so... but the window is down..

wait 7 minutes...  loosen the green knob.. so all the current draw goes thru the amp meter... OBD2 can keep some devices active for around 6 minutes...


normally this is 0.030 MilliAmps DC.. to 0.040 MilliAmps dc..


many cars have fuse box under the hood to start with...

pull one at a time.. . while noting or having a friend watch the amp meter display...


if you don't have a digital volt meter. these are like 20 bucks at HF... 37772.. i use them daily..  it has a 20 amp DC setting that comes in handy...



these are test leads that i put together.. you can create your own.. they don't come with telco test clips like this..



the first fuse to pull is the dome light fuse...

then the others one by one..

this is a tool.. usually 90 to 150 bucks... a low amp current probe... measures up to 40 amps..  but measures down to a 100th of an amp...  so you can just clamp over various wires to see which one has current flowing.. and it makes it easy to find the short...



don't forget to check the door switches... they keep the retained power relay active until a door opens and closes..

[57larry]

Wayne, that's got to be the best tech advice I have received in a long time. thanks, Larry

[wayne petty]

thanks. i do try to help...


a few things...

these are small amp testers... plug into the fuse box when you remove a fuse..  there are 2 versions.. one for ATO sized fuses and the other for the smaller fuses used on 2000 and newer cars...

http://www.harborfreight.com/20-amp-automotive-fuse-circuit-tester-67725.html

http://www.harborfreight.com/30-amp-automotive-fuse-circuit-tester-67724.html

watch the prices if you don't need them instantly.. once in a while they can be had for under 10 bucks..

you do have to move the removed fuse to the side of the connector for it to work.. or have a spare fuse in the hole.. better to use the existing fuse.. so there is no chance of an overloaded circuit..

guess what.. if you take one of the green knob battery disconnect switch.. and a fuse holder pigtail.. you could actually wire this tool up to either side of the green knob switch.. so you could have a second amp meter . to measure parasitic draws the proper way...

one could even use female quick connects and some wires..

[BFS57]

Hello;
Wayne, you always have at least one way to "skin a cat" and in this case at least a couple ways. Like I said earlier, Somehow Im thinking that the electric door convenience system is to blame for this problem. Thats the first fuse on my list!!

Bruce

[wayne petty]

Hello;
Wayne, you always have at least one way to "skin a cat" and in this case at least a couple ways. Like I said earlier, Somehow Im thinking that the electric door convenience system is to blame for this problem. Thats the first fuse on my list!!

Bruce

harbor freight has these switches.. you will have to find a battery cable and lugs to make one into two short ones..   and scrounge some banana plugs to hook to the amp meter.

don't hook the amp meter up until you have shut the engine down..  there is enough voltage drop to possibly damage the amp meter shunt or blow the fuse if its a fused version..

i use the Harbor freight 37772 multimeter as it has a 20 AMP DC setting..
and they are cheep..

[BFS57]

Hello;
I do have a battery shut off in the battery compartment. This may hasten things a bit when testing. I may have to make up some longer leads for the multimeter, because my battery is in the rear of the vehicle and fuses are in the drivers side. Fuse block is easy to get to after I take out the seat.

Bruce

[wayne petty]

lay a single jumper cable under the car on the ground.. as an extension for testing from the battery in the trunk to the front of the car..


did you have this voltage drop test.. i did not see a link for it above??


the most important test.. http://i.imgur.com/WMDprhm.jpg  not only for hot rods. but for daily drivers up thru brand new models..


http://www.allelectronics.com/make-a-store/item/tl-7/alligator-clip-test-leads/1.html

http://www.allelectronics.com/make-a-store/item/cb-225/6-cable-with-banana-plugs/1.html


then there are heavy duty double pole single throw switches like this..
http://i1207.photobucket.com/albums/bb476/waynep712/disconnectswitchwiriringwayne_zpsc5377a58.jpg