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parasitic draw W/ killswitch installed

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Mufasa

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so basically, i bought a new used car, the previous owners told me they had a killswitch installed to solve a parasitic draw, and save some money

i've been trying to diagnose & fix it myself, but i only have online guides to go on

what i've tried, basically is hook my multimeter between the negative terminal and cable, and measured the amp draw with the killswitch turned off (so power would go through), i get a reading of about 4 amps, which is too much, and abnormal as i can't turn on light/radio etc with it hooked up this way
i'm assuming the killswitch relay isn't getting the power needed to flip, i can't hear the relay clicking when i touch the contacts too (like i would hear when i flip the killswitch)

any ideas?
 
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FOUR AMPS?? :eek:

Okay, let's start. So without the switch, how much current is being drawn?

Also you can start tracing where that switch wire leads to. Obviously something connected to it is malfunctioning in some way. You could feel around for warm spots, and or listen if it is some mechanical part, which will tell you something is staying on.

Another way requires getting someone to help you test. Connect the multimeter like you did to measure current, but only have one lead connected. If you connected a lead, you will get 4 Amps drawn. So first you test, touch the non connected lead, to confirm 4 Amps drawing. If yes continue.

Remember to just touch it long enough to verify 4 Amps being drawn.

Now you go to the fuse box, and start pulling out fuses and relays one by one, each time quickly testing the amount of current being drawn. If current draw drops noticeably, like from 4 Amps to say 3 Amps, you have one found at least one culprit. If it drops completely then, well done! otherwise keep looking until all are pulled out, or current drops to something really small.
 
If you have one Ammeter lead connected to battery negative and are probing with the other lead there is a serious risk of destroying the meter and possibly burning out a wire :eek: !! Use a bulb in series with the meter to limit current and give a visual indication of the fault.
 
Often, pulling out the fuse from the fusebox then connecting the meter in series with the empty holder will let you determine which circuits are pulling the most current then you can refer to the manual as to which fuse does what and work back from there.

You may need to wait for a couple of minutes after hooking the meter up for the readings to settle though.

4 amps is a fair amount - maybe try disconnecting your alternator first and make sure it isn't a dead diode in there drawing the current ?
 
the previous owners told me they had a killswitch installed to solve a parasitic draw, and save some money
I other words a bodge!
Add complication rather than fix the original fault.

I hope you got this car for a good (cheap) price!

JimB
 
If you have one Ammeter lead connected to battery negative and are probing with the other lead there is a serious risk of destroying the meter and possibly burning out a wire :eek: !! Use a bulb in series with the meter to limit current and give a visual indication of the fault.
haha, i think i may have already blown a fuse in it, i don't believe it's permenantly damaged though
alas i know very little about electronics, i have held hobbies with circuitry now and then, i was under the impression that a major expence would be the time it took to pull fuses and record results

as for bypassing the killswitch, i'll have a look into that tomorrow, at the moment, i'm not entirely sure i've found it, i've found a much newer looking contraption indeed hooked to the negative terminal, and also hear it clicking when it's turned on/off, but i'ts cased differently than i'd expec (appears like a large motor/metal cyllinder casing), anyhow i'll have a look into it tomorrow, and upload some pictures
 
Also you can start tracing where that switch wire leads to. Obviously something connected to it is malfunctioning in some way. You could feel around for warm spots, and or listen if it is some mechanical part, which will tell you something is staying on.
i should tell you, the killswitch does seem to be working perfectly fine when it's not in series with the multimeter, i'm sure i just did something wrong, anyway, i'll try more stuff tomorrow
 
With that kind of current draw, I would theory disconnect the dome circuit so the interior lights don't come on and re-verify.

Another place to check that won't show up on a normal check is to disconnect the alternator. At least the battery terminal and the plug going through the firewall. (Be careful).

Then, I would re-connect the battery cables. My theory is, that you should be able to measure the voltage drop across the fuse using the two visible tabs on the fuse. An auto-range meter would help. The ones that read 12 V across the fuse don;t worry about. The ones that read mV ACROSS the fuse I would. Pull that one and see if the draw at the battery drops.

Remember that there may be multiple fuse blocks in the car. One car of mine had at least four and one was inaccessible without removing the panel.

If those tests fail, I would carefully check the owners manual to verify that you removed the right size fuse and I would remove 1/2 of the fuses. If it's still present, remove the other half. I would not normally say to do this, but it verifies that it could be somewhere else.

If it's in the first half, then insert 1/2 of those. So you keep bisecting until you find the right fuse. It will take a lot less measurements. 32 fuses would take about 7 measurements, not 32.
 
4 Amps does seem to be a lot at first glance, but it depends upon how new and 'feature-packed' the vehicle is.
Q - What exactly is the year, make and model of vehicle?
Another factor, associated with the vehicle age/features, depends upon the time at which the parasitic current draw is taken.
As more and more electronic control units began to be introduced into vehicles, the standby current draw obviously increased. Automotive technology has advanced quite a lot over the years, bringing bus systems into the mix and control units practically monitoring/supplying power to almost everything on a vehicle. IIRC, a high end 7 series (E65) BMW had around 70 different Electronic Control Units distributed all around the vehicle, each with it's own power supply. At the moment of connecting the battery, each ECU would be fully awake and consuming current. (This would be the same condition when initially checking the parasitic draw)
When the individual systems sense that they are no longer required to be in operation, such as there being an absence of ignition/accessory power feed, they shut down to a 'sleep' mode. The whole process, for a complete shutdown of non-essential systems, can take up to/exceed 30 mins on some vehicles.
The current consumption can be observed to drop gradually during that time, due to load-shedding, then a more-accurate reading can be taken once the reading stabilises.

As noted in previous posts, if the vehicle is an older, more basic model, try disconnecting the alternator first and measuring the drain Vs when the alternator is connected.
 
4 Amps does seem to be a lot at first glance, but it depends upon how new and 'feature-packed' the vehicle is.
I can't believe any fault-free vehicle would have an intended standby current of 4A. That would drain the battery in a day!
The whole process, for a complete shutdown of non-essential systems, can take up to/exceed 30 mins on some vehicles.
Wow, that's worse than Windoze :)
 
I don't believe the 30 minute thing, but do believe the "few minutes" because of all of the warnings splattered throughout the service manual for disconnecting the air bag system until at least 5 minutes have elapsed. That, I think, is nothing but the capacitance discharging slowly. You also don;t want to start the car with an air bag system disconnected. I think the wires are orange.
 
Perhaps I should have been a little clearer...
When first re-connecting the battery/taking a parasitic measurement, 4 Amps can be expected on some vehicles with a large number of ECU's.
Obviously, the current drain drops off as modules begin to shut down, but 'a few minutes' is not enough these days!
The lengthy wait time is also a PITA when diagnosing drains on those types of vehicle.
Don't believe how long is required?
Have a look at the links below:
**broken link removed**
http://www.aa1car.com/library/battery_runs_down.htm
http://www.jagrepair.com/images/AutoRepairPhotos/Current Testing.pdf

Those are just a few examples. Note the Jaguar wait time of 45 minutes!!
 
hi guys, back again, i'm fairly sure the current draw was just some safety feature of the killswitch, i should have some updates later, but i'm dealing with another car thing atm
 
Hello Mufasa!

I'm assessing you a ten yard penalty for failure to reconnect with all the members who labored over keyboards back in February in an effort to resolve your dilemma!

I noticed my buddy, K.I.S.S. weighed in and I can attest that he gets cranky in situations like this .

All seriousness aside, what was the resolution?

Was listening to Click n Clack on NPR recently and I believe I heard them comment that a late model car, sitting for more than 2 weeks will reward it's returning owner with a flat battery.

@ 4 amps, you would appear to have a major issue, unless that number declines with time, as others have noted.

So, what's up?

Best wishes.
 
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