FGZ

'85 4Runner, I've had a slow drain on the battery for months. It was inconsistent so I just dealt with it - be ready to jump start it if you leave it for more than a few days...sometimes. Recently it started draining the battery if I leave it for more than a few hours. So I've been disconnecting the pos terminal overnight and at work until I had some time to troubleshoot things. That's getting old and I finally have some time off.

I dove into it today, here's what I got.

Procedure:
1. Positive cable removed from battery
2. Multimeter connected to pos terminal on battery and to pos cable to look for amp draw.
3. With everything off, I'm showing about .12A draw.
4. Next, start pulling fuses to isolate the issue to a given circuit.

Findings:d
The underhood fuses made no difference, except for the giant green 40A but I assume that is some main fuse and isn't what I'm looking for.
Quick question, what is supposed to be to the right of there??



Under dash, fuse panel looks like this:



The cover says the fuses SHOULD look like this:



Let's ignore the varying fuse sizes for a sec.
Pulling the top right 15A drops the amp draw to zero, so that "STOP" circuit is where I should be focused. I think 2 other fuses dropped it by .01A each, but I'm ignoring those for now - I think it was bottom left (EFI) and maybe middle right (DOME).

FUSE SIZES - should I drop everything immediately and put all fuses back to their factory sizes? Seems like the right thing to do.


STOP CIRCUIT - where do I start? I'm not sure what culprit I'm looking for or how to test for it.
I'm showing .12A being drawn on that circuit, but I'm rusty on my multimeter so I could be using the wrong setting. I'll look into that, but that's definitely where to focus. Here is the schematic from the FSM:


Sorry that's hard to see, but it looks like the circuit is only energized when the stop light switch is closed and the EFI computer gets a signal (for cruise control I assume) and the rear lamps get lit. Sounds like that switch is the place to start, like making sure it's fully open when appropriate. Other thoughts?


Thanks,
FGZ

vital22re

iTrader: (2)

is there a trailer harness adapter installed?

FGZ

I don't think so, that's something I'll check on.

Aftermarket stuff is winch, ARB air compressor, and radio. I checked around the winch a bit before going to fuse panels, I get the same amp draw on the positive lead of the winch so I need to look at it again too

muddpigg

iTrader: (1)

X2 on trailer circuit. Mine was cut off when I got truck, but was intermittenly shorting from old cracked wires.

wyoming9

iTrader: (1)

Since you got it down to the brake light circuit Pretty simple circuit .

Has your brake light switch failed . Brake lights on all the time??

Shorted via the bracket ?

A short in this circuit should open the fuse.

Another thing could it be your battery is getting old and no longer holds a charge like it should .

I have also seen poor grounds cause this to happen something that is powered all the time grounding through the brake light circuit.

FGZ

Thanks guys.

I don't *think* the brake lights are on full time, hopefully I wouldn't overlook that. But if that switch is easy to access I'm inspecting it.

Battery is 2.5 years old, but was used when purchased. It's a gift from the PO I suppose - I've only had the truck a year. So it's not the greatest, but it holds the charge if I unplug it.

So out back I'm looking for:
-split wires
-bad grounds
-funny business around any trailer wiring.

FGZ

Also, I have always had a fast blinker. Reading through the FSM, I'm supposed to be 75-90 per minute and it will double if there is an open circuit in the rear. I'm pretty sure I'm closer to 120 flashes per minute. I wonder if I will fix 2 things at once here.

FGZ

I can't see any trailer wiring stuff present.

I had cracked/missing insulation on wires in both taillight assemblies where the PO had tapped into the wires for something now missing. Taping those back up didn't change anything though. Completely disconnecting both taillights did not change anything either, still have a drain of about .36A...up from the original .12A but maybe the recent rain changed something.

I think I'll look behind the fuse panel next then look at the switch.

grumpin

x2 on the trailer circuit. I would look up by the rear lights where the adapters hook up. My clock would dim when I hit the brakes, had to replace the one that was there. And x2 on the battery, lots of times they appear good but are not. I would definitely put the correct fuses in.

On edit: Oops! Sounds like you checked where the trailer harness would be, or more than likely was.

FGZ

I think you're right, I checked where I think it would be - all that was there was a break in the insulation where a (now cut) wire was wrapped around the exposed wire. Those insulation gaps are what I taped up, but like I said it made no change even when I unhooked both taillights completely.

Is that how trailer lights are usually wired up on an older vehicle like this? Just find the light you want and tap into it?

I haven't had any more time to troubleshoot it and the weather is only getting colder, ugh.

About the battery health - no it's not the best but as long as I leave it unhooked it turns the truck over nicely, and I don't see how a bad battery would throw a slight load over a circuit that is supposed to be closed.

grumpin

The Hoppy brand was a popular trailer hook up for all sorts of vehicles. They used those snap together connectors. Can't remember what they are called. Thats what my 4Runner had. Found a part number that works in the forums on the 4Runner but wasn't listed. But was listed for the pickups. And it connects into the lighting circuit. It is also a Hoppy brand, and there are equivalent hook ups by other brand names. Yeah, these are weird, it has to be a draw, like a stereo or clock. If it was lights you would think you could see it when its dark out. I understand your battery seems good, but wouldn't rule it out. If your battery has an internal short or something it could be the draw. Do you have another battery you could stick in there and see if you get the small amp draw? I had a battery in a 68 Chevy pickup that I thought was great, lasted a long time. It was just that the truck started so well, it never worked the battery. Had someone pull out in front of me and I hit the brakes and stabbed the clutch, it flooded the engine. Cranked for a bit and the battery just died. Not the same scenario, but I learned to test them if I could, or stick another battery in to test it. Also might test your multimeter on another car to see if its reading correctly, leads could be giving you the draw. Even if pulling fuses makes it go away. I've seen multimeters do weird things. I would think if something in the stop circuit was shorted it would blow the fuse. Sorry I'm long winded, these problems are head scratchers! Good luck!