Hello all,

Until yesterday, the truck has been fairly flawless.

I went to start it, and the battery was completely dead. As the battery was a few years old, I thought at first that it might just need replacing, so, as I had a trip to the dump to make with an already loaded up truck, I took a battery out of one of my other cars and made the trip.

In the meantime, I charged the Toyota's battery, and it took a charge without issue. So, the next day, I went to drive the truck down to the garage to swap the batteries back over, and the temporary battery was now completely dead!!!

So, as there is nothing obvious that I have left on (ie. lights), I assume I must have a parasitic drain.

How should I start to track this down? One other note, that could be entirely coincidental, is that the horn, which has not worked in quite some time, started working on the first day of the battery drain.

Thanks for any tips or ideas on how to trace the drain. Is it possible that a critter might have chewed on some wires in the engine compartment to cause this???

Julian

 

It's possible that the wiring harness is sitting on your steering column and that has caused some wear based on some stories I read.

Here's how I tested my truck's harness for shorts:

Disconnect the battery and remove it for everything that follows
Open fusebox behind the battery tray
Snag a multimeter and set it to the 200 ohm range
Connect negative multimeter to negative battery cable (again, battery is out)
Connect positive multimeter cable to the positive battery cable

What is your resistance measurement? It should not be anything. Anything in the 3-30 ohm range could be your drain. .1-1ohms would be a darn near short.

Removing the 80A fuse link will let you even further isolate the issue. You press the tab behind it towards the firewall and push it down and out. It's a lot easier with the box out, but that is an optional step.

With that 80A fuse removed and totally disconnected, taking an ohm reading from your positive battery terminal will show if the drain is in your starter wire or starter.

Taking an ohm measurement from the ring terminal on the large white wire that connects to the 10mm stud on the back of the 80A fuse to ground will allow you to test if your alternator or it's wiring has an internal drain. I will suggest that a partially shorted field winding in the alternator could be the cause of your symptoms. That's easy to test for: disconnect the white wire from the top stud on the alternator and then check ohms from the engine block to the top stud with range set to 200k. It should be in the 10's of thousands. If it shows something in the 3-30 ohms range, it's time to change it out before fuses start popping.

Taking an ohm measurement from the ring terminal on the smaller white wire that connects to the 10mm stud on the back of the 80A fuse to ground will allow you to test if your drain is in the cabin or engine harness. You can further isolate an issue in those harnesses by removing the fuses in the driver's kick panel one at a time and noting when the ohm measurement disappears.

Taking an ohm measurement from the red/blue and red/green wires that hook to the front 8mm studs on the 80A fuse to ground will allow you to test your lighting circuits for the drain.

Hopefully this helps. I can probably be more specific if you can isolate which part of the wiring the drain is in. I learned a lot on here this week!

And on a "weird problems" note, I've read about of a few folks who had oil that leaked down into the reverse switches on their transmissions causing drains and ultimately blown fuses. Heck, I lost a few open frame starters on a Ranger to a leaky valve cover in my youth...

 

Thanks for all of the insight. I will try this on my next day off (not till Sunday!) and report back.

Thanks again!
Julian

 

I pulled out the multimeter today, and connected it to the battery (in series with the negative terminal). So, the positive truck terminal was connected to the battery; the COM wire from the mult meter connected to the negative truck cable (disconnected from the battery) and the RED mult meter wire connected to the negative battery terminal. wff---I forgot about the alternative way listed in the comment above---sorry! I will have to, now rereading the comment, perform the test on the 80A fuse and alternator too as mentioned.

For now.....

With nothing turned on, the reading was 7.8 mA draw. I then, one at a time, pulled the fuses from the kick panel area of the drivers side floor.

None affected the draw except for the DOME LIGHT fuse.....that dropped it to a 3.2 mA draw. This fuse (upon checking things out) appears to at least control the door buzzer, the clock, and the dome light. The radio appears to be on another circuit.

Then, I pulled, one at a time, fuses from in the engine compartment. The HAZARD HORN fuse further reduced the draw to a total of 2 mA.

So, any thoughts on where I should go from here? What should be a normal draw when the truck is off (base model, only a factory digital clock and then the car stereo/clock I would imagine should be pulling power when the truck is off)??

Thanks for any thoughts,
Julian

 

That’s very little parasitic draw. I wouldn’t expect any problem there. Maybe your battery is just beat. Mine is about 30 mA draw if i remember correctly, due to the sense lines to a couple power amps.

 

It would take weeks to drain a good, charged battery at a 5 or 10 milliampere draw.

 

Honestly, I too thought that. But it killed both the battery in my truck in 1 day, and then, when I swapped the battery out of another car simply to go run an errand, it had killed that one too in a day when I went to start it up! Both batteries took full charges fine after being depleted.. Both are working fine (well, when I need the truck and it has to sit, I have been quickly disconnecting that battery).

I wonder if I have misread the mA and it is actually amps? Both voltmeters I used read the same (1 cheapo from HF and 1 older quality one from Snap on), but I am not a pro either at using them!

Julian

 

fwiw, here is a circuit diagram for a hazard horn fuse, not sure if it's exactly like yours: https://www.yotatech.com/forums/f199...l#post52242207

 

Thanks all for posting.

I decided to connect the battery for half a day to see what happened. Almost no change in voltage.....same for letting it stay connected over 24 hours. I have been driving it since with no issue. Not sure what caused this anomaly, but it seems to be fine.

Julian

 

All has been fine for a few weeks, and then this morning, the battery was dead again. The truck only sat for 3 days! This is bizarre, as it makes no sense.

I am charging the battery as I write this, and then will see what draw I get again using the multimeter.

Not sure how it can be fine for weeks, and then return again after only a 3 day rest (and there have been several of those over the weeks).

Julian