FJ62 battery draw diagnosis...normal or not?

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Skniper

Skniper

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Suffice it to say I'm no electrical genius, bear with my simpleton ass. I've been reading a bunch of "battery drain" threads looking for answers to what I suspect is a parasitic battery draw my fj62 has had for a loooong time.

I set my digital multi meter to DC mA, disconnected the positive battery cable and jumped the meter between the pos battery post and pos cable. I got a consistent reading of 0.16 mA (first pic).

Reconnected battery cable.

Pulled every fuse one by one and jumped fuse terminals with meter. All read 0(zero)mA, with two exceptions. The 15A EFI fuse in the lower left corner of fuse bank gave me 0.15 mA...further reading in the threads indicates this fuse is always hot and controlled by the EFI relay by air cleaner. Had my daughter switch the ignition key back and forth and I could feel the EFI relay cycling on and off, so it appears to be ok.

The other exception was the usual culprit Dome fuse (manual lists it controlling "Interior light, luggage compartment light, inspection light socket, clock, key reminder buzzer") It also rang up 0.16 mA(second pic). This fuse as I understand should be "hot" too since it runs the clock. But how hot is too hot?

I pulled both EFI and Dome fuses and rechecked the battery cable, got about 0.08 mA with both out. Not sure what that means.

So, are these two fuse draws reading too much?...or within normal ranges?? Is there another way to check draw with the meter?....any thoughts or suggestions to look elsewhere much appreciated.

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No electrical expert here either, but there are 1000 milliamps in 1 amp, so .16 mA is an extremely small draw (16/100000 of an amp). I would say there is not a problem here.
 
Apparently your duplicate post on this last night was deleted. I posted on that one last night. As already mentioned, you measured 0.00016 amps. That's not a parasitic draw, and likely lower than the self-discharge rate of the battery. Your methodology at the battery was okay, but jumping between the disconnected negative cable and the negative battery post is safer for the meter. A short to ground while connected to pos like you did will pop the fuse in the meter, or fry the meter if there's no fuse. (The meter is likely rated at 10 or 20 amps max and the battery is capable of 600 amps +) The numbers derived are the same, though. I'd keep the meter connected at the battery while pulling fuses instead of testing at the fuse box like you described.

You should see less than about 50 mA, and if you see zero, check the meter connections because you should see some draw. On more modern luxury rides, there will be some systems that remain powered up for a specified time after the key is off.

What symptoms are you seeing that lead you to suspect a parasitic draw?
 
When you set your MultiMeter to measure current (Amperes) and get a reading as you did, then the circuit you are measuring is complete, and current is flowing.

So then the question is, under the conditions which you took the measurement, would you expect:
1) the circuit to be complete
2) the value of the current you measure to be on the order of magnitude you would expect to be flowing through the circuit (the 'draw' of the 'load')

In the case of the 'Dome' light circuit, when you took the measurement, was the Dome light in the vehicle cabin illuminated? If so, I presume the driver's side door was open, which would close the switch that in turn illuminates the Dome light (if the switch at the dome light itself was also closed).
If so, then the answer to question 1 would be yes, you would expect to measure a current on that circuit under those conditions.

Then the next question would be, is the value of the current that you measured on par with what you expect the Dome light bulb (the load) to be drawing?
The power that a load (electrical component/device) draws (demands) is measured in Watts (W).

W = I x V

where I is current (in Amperes) and V is volts (in Volts)

This circuit is a 12V DC (direct current) circuit - since it runs off the vehicle's battery, which is 12V DC

If the wee Dome light bulb is rated to draw 2 mW (milli Watts or 2 x 10^-3 Watts), then the current you would expect to measure flowing through that circuit when it the bulb is illuminated is:

I = W/V or I = (2 x 10^-3 W)/(12 V) = 1.67 x 10^-4 A = .167 x 10^-3 A = .167 mA

which is what you measured.

So, when you took the measurement on the Dome light circuit:
1) was the Dome light illuminated?
2) is the bulb on the Dome light rated at 2 mW (should be stamped on one of the metal contacts of the bulb itself)?

And, if you retake the measurement of the Dome light circuit, but with the doors closed (so the bulb is not illuminated), what the value of your measurement (in mA)???

With respect to the other circuit where you measured a current, I think you called it the EFI, I was not able to find this component/circuit on the wiring diagram in the "Landcruiser chassis-body-84-90 Repair Manual.pdf".
Is your FJ62 stock? What motor is in there? Can you post an image of the circuit from the wiring diagram or name other components that are on that circuit?
 
If the wee Dome light bulb is rated to draw 2 mW (milli Watts or 2 x 10^-3 Watts), then the current you would expect to measure flowing through that circuit when it the bulb is illuminated is:

I = W/V or I = (2 x 10^-3 W)/(12 V) = 1.67 x 10^-4 A = .167 x 10^-3 A = .167 mA
Click to expand...

The problem with this math is that dome lights draw more than 2mW. The stock bulb is around 6 Watts, so it would draw 500mW. Even a LED replacement draws around 35mW.
 
Cruzerman said:
The problem with this math is that dome lights draw more than 2mW. The stock bulb is around 6 Watts, so it would draw 500mW. Even a LED replacement draws around 35mW.
Click to expand...

Correct, well, actually the math is right, it is the assumption that the bulb, when illuminated, draws 2mW that is wrong. That is why I was wondering whether the circuit was complete (in other words, drawing current through it to illuminate the bulb) when he took the measurement.

I'd still like to see a comparison of measurements taken with the door open (circuit complete - bulb illuminated) and door closed (circuit open - bulb not illuminated). I think there are also other components behind that fuse on the circuit.
 
Slow left-

Thx, all good food for thought and tips to check stuff. Can't give you any solid answers on retesting the dome as I'm away from the truck for a few days.

Back to the symptoms leading to this...for numerous years I've suspected this truck is a battery killer. That said it has also, off and on, over the years been a second or 3rd vehicle or DD. So it will sit for extended periods at times...i.e. the worst thing for a battery.
Back when Optima batteries were developing a bad rap I went through about three red tops at random intervals. Optima quality problem? Coincidence?...dunno.

On my second DieHard Platinum grp 65. First one was 5 weeks past warranty, dude at Sears gave me a new one no questions. Bam!
Alternator has been replaced with OEM as needed a couple years ago. All ground straps replaced with a beefy set from Urban Land Cruisers several years ago.
The only after market stuff is a pioneer head unit & speakers and a qeniuine 3FE List Wayne Tangen headlight harness.

Also considering running a direct wire from alt to battery.

Based on the little draw I'm seeing through the fuses, I may just be chasing ghosts. Probably just need to drive the damn thing more often, eh? Good learning experience chasing this stuff down though.
 
Alright. Yeah, if you can retest the Dome light circuit and take current measurements with the Dome light illuminated and not. Like Cruzerman notes, you would expect to see a measurement of 500 mA when illuminated if the Dome light is drawing 6W (if the rating on the bulb is stamped 12V 6W).

That said, I'm thinking it might not be as simple as measuring currents at the fusebox in order to identify stray current leaks. Because, as I mentioned above, when you test the circuit by measuring current, you must understand the circuit to expect to read a current flowing at that specific point where you are measuring for it and under the conditions of the circuit which you are measuring.

For example, you mentioned that you only measured current on two circuits. But if, on one of the circuits that didn't read a current at the fusebox, if you should expect to see a current but there was a short in front of it (between the + battery and the fusebox), then your reading of 0 current at the fusebox would actually indicate that there is indeed a stray current...a short in front of the fusebox.

I'll try to come up with a better way of explaining it, but essentially, you're going to have to be very thorough and measure each circuit under different conditions (switches open/closed) and at various points (before and after switches/components) starting from the grounds of each component and working back towards the battery in order to identify components or wires that might be 'leaking.'
 
Long story short here I'd be suspect of your head unit (CD player) or a cold joint solder or a dodgy fusible link.
Your meter wouldn't really have the resolution to read what you're looking for and I doubt between the lead resistance and the connection to the source you are getting anything worthwhile looking at.

The 60 series in reality is a big hunk of conductive steel with negative switching going right the way through it so at any point in time positive leakage to negative potential is pretty likely and as wire insulation breaks down and aftermarket electrical gear is introduced you will undoubtedly get vampirism.

Realistically if this is happening over a period of weeks there is not much that can be done. Maybe try pulling the accessories fuses in the cab while it's not being driven and see what's happening there.

You've made some really good first steps for someone who says they know nothing about sparks.
 
Throw a heavy duty switch on one of the battery cables, when it is going to sit for an extended time, shut it off. Or just pull the neg. cable.
 
Has this problem ever been resolved?
 
I have a buddy that has a '90 62 that has had the same slow parasitic drain problem for years. He has never been able to fix/find it, nor the shop he took it to. To add insult to injury, Toyota's engineers gave the 62 a double whammy.. when the battery is disconnected entirely from the system, aka big battery switch, the ECU loses it's volatile memory (regarding driver habits) and has to re-learn them all over again (takes a week or so) during which time the engine runs less efficiently than before.... At least that is what he told me... and Toyota told him.... after banging his head over the issue for a long time.. I don't have first hand experience with the 62, so this is all second hand. (I have a 60).
 
Sounds a bit scary that he never was able to fix the problem. I hope I can tackle mine
 
Not so scary. Lots of cars of different makes have this "feature", to put it nicely. It is a fact of life for many modern cars. Just web-search "parasitic battery drain" 197,000 hits... ugg.
Along with my 60, I have an older Subaru & it has the same parasitic battery drain problem .. a few mA constant drain that eventually kills the battery if the car is not driven for a while. I have not been able to eliminate it, short of a big battery switch, which causes other issues.

The Subaru dealer's official recommendation was "You need to drive the car more often." An independent mechanic I took it to gave me the same recommendation. The only way I have been able to deal with the issue is....... drive the car more often... or hook it up to a trickle charger.

If the slow leak can not be fixed, and the car is kept outdoors, a workable solution that will keep the battery from discharging is a dash sized solar panel.

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Or this (if there is power)
trickle-charger.webp
 
all of the recommendations sound good to me but my truck's batteries discharge in a matter of hours. Anything above 10 hrs will weaken the batteries to the point where the 2h cranks only once or maybe twice. Hopefully I will be able to fix it
 
Tried to find the same solution to the same problem with no result, ending up just putting on the trickle charge every 3 - 4 weeks.
 
A lot of the time this is just the battery dying after it's been run flat one too many times but it would hurt to check your glow plugs out along with the buss that connects all the plugs, sometimes the insulator on the back plug can start to break down to earth and create a leakage path.

Also check fusible links and the conditions around the battery incl. water levels / specific gravity and terminal and connector condition and cleanliness.
 
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