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Verifying draw in vehicle when off...

Matt Bachand

Matt Bachand

Depends on the 6.5
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There was a way to use a test light to verify that something in a vehicle is drawing juice out the battery while vehicle is parked overnight.

something about hooking it up backwards at the battery or ...

I cannot remember how. Someone refresh my memory please!
 
Remove negative battery cable (both negatives with a diesel) and put the test light in series between the battery post and the cable if the light comes on there is a draw. Dim=small draw, bright=larger draw. Sometimes you have to wait in the case of interior lights that are on a timer delay until the light would go out, as you won't see the light on.
 
you will have a couple of small draws. the radio, PMD/FSD, and I know I'm missing something. are you having the batteries drop right down at night?
 
Mudbath said:
Remove negative battery cable (both negatives with a diesel) and put the test light in series between the battery post and the cable if the light comes on there is a draw. Dim=small draw, bright=larger draw. Sometimes you have to wait in the case of interior lights that are on a timer delay until the light would go out, as you won't see the light on.
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In series between neg battery cable and pos battery post?

Oh, in between teh removed neg cable and the neg post.
 
alot of the same things apply. just about anything from the '90's up have all the computer stuff n them. they draw a small amount for them memory.
 
No, between the negative battery post and the negative cable. If there is no current from anything the light will not come on, but as other poster said, there maybe normal slight draws but should only be a dim light.
 
Flashes quick, then dim. when i take it off it seems to charge up that initial quick burst. Like u said, battery memory, other draws are possible.
 
A more extensive investigation can be performed with a test light. Open the fuse panel, and pull the fuses one by one. Run the test light across the two contacts in the fuse panel when the fuse is pulled. If it lights up, then there is draw on that circuit.

Using a multimeter works better. Set it to read amps. Check for the total draw between the negative cable and the battery negative post, then go to the fuse box, and probe one fuse at a time until you have found the draws that add up to the total amount.

Anything that cannot be found in the fuse box will require a wiring diagram to track.

Good Luck!!!
 
you should use a multimenter in series to really read the draw, it should be well under an amp so a digital multimeter is helpful. Just dont do it with the key on, because a lot of the cheap meters can only handle like 2 amps.
 
Turbine Doc said:
What is wifes vehicle, VW TDI, those have such a parasitic shutdown load VW issued solar charges for your dash to keep batts from dying
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2000 Hyundai Accent :) Paid for and fills up on 12 bux :)

New battery, disconnect it before bedtime and batt holds the charge. Leave it connected and dead 90% of time when cold overnight.

Test light verifies a draw, not extermely bright, kindof has a rythm to it. Starts bright, then dim's, almost pulses once. Once i remove the test light and hook it back up in series to the neg circuit, it goes on bright as if it charged itself a tad, then pulse, then dimm. Repeat touch is nothing. Wait a few seconds and bright, then pulse, then dimm, until off.
 
First thing to check if you are showing a parasitic load is pull the charging wire from the alt. If the load goes away the alt is bad. I've had diodes go bad in several. Charge the batteries just fine when the engine is running but kill the battery when off.
 
it goes on bright as if it charged itself a tad, then pulse, then dimm
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Somewhere in the vast electron highways and byways of you truck's electrical system there's a capacitor charging up. Once charged they're happy and don't draw anymore current. I can't imagine how that would pull your battery down to nothing.
Either the batteries are bad, or one is bad and killing the other one, or something is drawing current steadily. Your test light would indicate that you don't have a steady current draw. OTOH - A test light is great for finding short's, a VOM is THE basic electrical troubleshooting tool.
Go get either a VOM (Volt, Ohm Meter) - either digital or analog - and start ferretting out your current draw.
They don't cost much, are available at any Home Depot type store, and are an invaluable troublshooting tool.
A digital meter is easier to read, but an analog version's display responds much faster giving you a better picture of what's really going on. I way prefer analog meters, but they have 2 basic problems... You have to know what your looking at and for. Putting it on the wrong scale can blow the meter movement (mechanically, usually) AND most times dropping it will ruin it. Most digitals are pretty much bullitproof. If you don't care what it looks like, you can just throw a digital meter in your tool box. A good feature :)
 
RadioMan said:
Somewhere in the vast electron highways and byways of you truck's electrical system there's a capacitor charging up. Once charged they're happy and don't draw anymore current. I can't imagine how that would pull your battery down to nothing.
Either the batteries are bad, or one is bad and killing the other one, or something is drawing current steadily. Your test light would indicate that you don't have a steady current draw. OTOH - A test light is great for finding short's, a VOM is THE basic electrical troubleshooting tool.
Go get either a VOM (Volt, Ohm Meter) - either digital or analog - and start ferretting out your current draw.
They don't cost much, are available at any Home Depot type store, and are an invaluable troublshooting tool.
A digital meter is easier to read, but an analog version's display responds much faster giving you a better picture of what's really going on. I way prefer analog meters, but they have 2 basic problems... You have to know what your looking at and for. Putting it on the wrong scale can blow the meter movement (mechanically, usually) AND most times dropping it will ruin it. Most digitals are pretty much bullitproof. If you don't care what it looks like, you can just throw a digital meter in your tool box. A good feature :)
Click to expand...


I haev one, its not my truck, wifes little car, small battery. Usually brings it to a slow crank or 2 in morning but not enough to start. I have an old digital one.
 
well a 2000 time for them gnd germlins to start rearing their ugly head, for it to go down overnight, would have to be a healthy draw, is batt good, you test with a load cell ???, partially sulphated plate even though charges good won't hold up, you have DTRL on that car, if so put on parking brake to disable between cranks and see if it improves slightly.

Computer or parasitic load should not kill it overnite, rear window defog could if it's not cutting out, a window motor or door lock solenoid might if staying full time energized, is there an underhood trouble light not turning off ?? IMO has to be a high current draw device or a short to kill overnite if batt isn't healthy and gnds are bad.

How is cranking speed on starter, healthy bad winding in it could zap bat quickly as well during start.

Just had another thought, fuel pump energized all night, eventhough not pumping ???, seat motor, those kind of big draw items would be where I'd look once you check out rest of stuff
 
if its an old battery or not maintenance free check the water level, as no water will mean it wont hold the charge. And cold makes it worse.

And like Turbince Doc said would have to be big draw if the battery is healthy.
 
The guy who fixed my head looked at it today and tested the alternator and it was putting out 16.8 volts. Had it rebuilt for 100 bux, which is awesome on a hyuyndai as they are 240 new.

I have a communication problem with him, so I don't know if he properdiagonsed it for the draw, but that voltage is too high, so the regulator crapped out. We'll see tomorrow morning if she starts up.

Its the wifes car, It feels like a go-kart to me after driving around in my rig all day. I could literally park it in the bed of my truck. Its great on fuel though.

Actually you can see it in my avatar. LOL, its tiny. But so is the wife, she's only 4' 11, 105lbs.
 
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