Fuse pull test by electrical dummy (1 Viewer)

[lxj1]

I think I have a parasitic draw that has drained my battery. I have a cheap multimeter from Harbor Freight and my knowledge of electricals is worth just as much.

I could use some hand holding to do the fuse pull test. I’m an electrical dummy so please don’t laugh!

Am I doing this first part correctly to see if the amperage is in normal range?

 

[Malleus]

If the negative (Black) multimeter lead is on the positive battery lead, no. Once you pull one or the other batter terminal leads from the battery, there is no longer a circuit.

For what it's worth, it's a good practice to always pull the negative lead, that way you completely eliminate the risk of electrical shock. If the negative lead is connected to the battery, and you touch the unconnected positive battery post and also touch the truck, you complete the circuit and are then a part of the wiring harness.

Think of the "circuit" as a "circle"; if it isn't closed, it's not a circle. Same for the circuit; you have to have a closed loop.

 

[Malleus]

I'd first check the alternator. If you can't remove it, at least check the voltage across the battery terminals while the engine is running. You should get 14 or more volts DC. If you have aftermarket accessories installed, you should look there first. If not, I doubt you have a parasitic draw (although it's not impossible); it's more likely a bad alternator. Any auto parts store can check the alternator for you, but it has to be off the truck.

 

[Malleus]

There is also a very good troubleshooting section in the FSM.

 

[yngmrostrvile]

If you are looking for a draw you are correct. Just make sure your key is not in the ignition and no doors are open. Give the modules 30 minutes to "go to sleep" then start pulling fuses slowly while monitoring your meter. Once your meter hits 0mah plug back in your fuses and start unplugging components on that circuit. Just make sure you give time for the modules to time out, key not in the ignition, and doors arent open..again.

 

[DBULL]

I may be wrong but isn’t that the setting for testing capacitors?

 

[jerryb]

it's to test 9 volt and 1.5 volt batteries. I did just go look.
it also looks like the red lead is in the com port.
OP black to com port, red to middle 200mA port, if that's what it says. I'm not sure. dial to 200m DCA

 

[yngmrostrvile]

Yeah, sorry the multi meter is set wrong. Red plugged to 10A along with multimeter.

 

[DTCsk8er]

As the others already said.. wrong port for the test lead.. and in wrong setting. I have one of these HF units, and it's pretty damn good in a bind. I keep it in the tool bag when I dont want to lug my Fluke around.

I've never measured my cruiser, but on other vehicles I've owned I see pretty much nothing (<30mA or 0.030A) of draw with everything off and the car sitting for a while. Make sure you dont judge things off the first value you see when you hook the leads up.. gotta let things settle.

Also, for basic circuit debug, you could check static current, and if it is high, begin by pulling a fuse out, noting current difference in current, then putting it back in.. keep going through each circuit until you find the culprit. You could also hook the test leads in substitute for the fuse, and read current right at the fuse box..

 

[lxj1]

OP black to com port, red to middle 200mA port, if that's what it says. I'm not sure. dial to 200m DCA

Here’s a more complete pic. Hopefully the meter is set up correctly now.

I read somewhere I should detach the negative cable and place the leads between that cable and the battery post. Assuming that’s correct I’m supposed to see less than 50mA but obviously I messed up somewhere.

Still feeling like an electrical moron so please take it one step at a time!

 

[lxj1]

I think I figured it out how to use the multimeter for current. This shows 560 milliamps which is too high when the car is cooled down, keys are out and no lights are on, correct?

 

[jerryb]

Not of it's not asleep. I was thinking it should be mid 40, don't quote me. I'd go do it and check mine but I don't want to take off the post. I'm not sure where the FSM says the number either, or if it does. Mid fives is probably fine.

 

[lxj1]

I was thinking it should be mid 40, don't quote me… Mid fives is probably fine.

According to this forum it seems the draw when asleep should be less than 50mA but mine is at 560mA.

Here were my steps:

1. Let car sleep overnight.
2. Leave key far away since I read here that having it nearby can wake up the car.
3. Checked all accessories were off including auto headlights.
4. Pulled each fuse from fuse box under hood. Amps did not drop.
5. Shut door latch and clamped down open door sensor.
6. Pulled each fuse from kick panel fuse box. Amps did not drop.

A few other things that may be worth mentioning:

• Did not pull the two bigger fuses on the positive battery terminal since they were on tight.
• Coolant gauge stopped working recently.
• CD cartridge in the middle console does not eject. I read here that a faulty one can be a cause.
• The HF multimeter in my last photo is a new one so hopefully that reduces the possibility of a faulty one.

What now?!

 

[medtro]

Deleted

 

[jerryb]

you're right, according to your pic of the meter and reading it's .5 amp. SO. I guess i'd do it multiple times over a day to make sure I get sort of the same reading. Normally I switch to another meter and verify.
If you want to get really crazy remove the radio, amp and NAV-DVD and lookup where the cd changer fuse is if you have one. Remove those and try again. I've almost never put volt meter leads across fuse box slots. I do know there are parasitic draw threads that are worth reading in the 100 section.



If you buy cheap volt meters it's good to have a few. I'm sort of like that. I have 4 cheapies at the moment and they're always rotating + one in the truck.
Current favorite for what your doing and me personally checking continuity on harnesses is one that's auto ranging with function buttons.

 

[CorporalClegg]

According to this forum it seems the draw when asleep should be less than 50mA but mine is at 560mA.

Here were my steps:

1. Let car sleep overnight.
2. Leave key far away since I read here that having it nearby can wake up the car.
3. Checked all accessories were off including auto headlights.
4. Pulled each fuse from fuse box under hood. Amps did not drop.
5. Shut door latch and clamped down open door sensor.
6. Pulled each fuse from kick panel fuse box. Amps did not drop.

A few other things that may be worth mentioning:

• Did not pull the two bigger fuses on the positive battery terminal since they were on tight.
• Coolant gauge stopped working recently.
• CD cartridge in the middle console does not eject. I read here that a faulty one can be a cause.
• The HF multimeter in my last photo is a new one so hopefully that reduces the possibility of a faulty one.

What now?!

The next step would be to connect the battery back and measure the voltage drop across every fuse. Just put the two leads across the top of the fuse and record the millivolt reading. Use this chart to determine the amount of draw.

You'll want to open all the doors required for accessing fuse panels and use a screwdriver or something to close all the latches, hood included if there's a door ajar switch. Let the car sit for 25 - 60 minutes (usually) so the modules go to sleep before you start taking readings.

(A trusty meter is necessary you'll be looking for anything over 1 mV so accuracy is key here.)

 

[lxj1]

The next step would be to connect the battery back and measure the voltage drop across every fuse. Just put the two leads across the top of the fuse and record the millivolt reading… A trusty meter is necessary you'll be looking for anything over 1 mV so accuracy is key here.

Thank you, @CorporalClegg.

For my education, can you or someone expand on why this step would help me identify the parasitic circuit when my previous step (measuring current in-line while pulling fuses) did not?

The concept seems the same to me so I’m obviously missing something!

 

[CorporalClegg]

Thank you, @CorporalClegg.

For my education, can you or someone expand on why this step would help me identify the parasitic circuit when my previous step (measuring current in-line while pulling fuses) did not?

The concept seems the same to me so I’m obviously missing someThis can cause modules to wake up during your test or worse cause a bad component in a group of parts on the circuit to stop doing whatever is doing that is drawing current.

This way you're looking for a circuit with excessive current draw just the same as fuse removal test while keeping all circuits complete.
Half amp is a pretty good draw, you could next test or substitute the Battery. Also need to confirm the starter and alternator, Those will be on large fuses I usually pull the charging wire from the fuse box or off the components themselves (careful not to short them to ground).
Don't over look the door switches, they usually short and give you door ajar warnings. Removing thoe switches from ground to eliminate them from the circuits. Be sure you've checked every fuse.

 

[lxj1]

Fuse pull and volt drop approach isn’t helping me progress in identifying the parasitic draw.

I noticed recently that the front passenger door lock was not working sometimes. I’ve read the threads hear about the door actuator possibly causing a parasitic draw. I decided to focus on that by pulling the fuses for the door lock circuit.

This website told me the location of the fuses for the power door locks:

Fuse Box Diagram Lexus LX 470 (J100; 1998-2002)

Fuse box diagrams (location and assignment of electrical fuses) Lexus LX470 (J100; 1998, 1999, 2000, 2001, 2002).

fuse-box.info

So I pulled fuse number 19 circled here from the engine bay fuse box:

And fuse number 32 from the interior kick panel fuse box:

I waited a few minutes in case it needed time but the in-line current draw remained high at about 500 milliamps. Does this confirm the door lock is not the source of the parasitic draw?

Next thing I may check is the coolant temp sensor since my gauge is stuck at the bottom. Is it possible the coolant temp sensor could be the source of the parasitic draw?

 

[Mike NXP]

I might have missed it, but what makes you think you have a draw? Start with the basics and make sure your battery and charging system are operating properly.

What is your battery voltage after you shut down the motor?

How about 12-24 hours later?

With the engine running, what voltage are you getting at the battery?