View Full Version : Current Drain '85 4Runner

02-24-2007, 11:04 PM
I'm running out of places to check and I was wondering if anyone had any suggestions. Here's what I have done:

I'm having trouble starting my truck every week and so I checked what the current flow was through the battery when the ignition was shut off. I've been told that it should be 25-50mA. I found that the current drain was > 13A! So to trouble shoot this I pulled each fuse (engine compartment, driver's side, & passenger's side) and checked the current leak (except for one, see later note). I pulled the alternator cables and the starter. No change. I even pulled the heater, power window, and tail light relays, just in case they were bad. Nope.

The 80A fuse in the engine compartment is stuck. If I could pull that I could further isolate the problem, but I am afraid of breaking it. Checking the schematics, there are two "busses" that go directory from the battery and downstream of the 80A fuse. With a bit of sleuthing, I came up with two possible areas to check: the main and cold mixture relays. I can't find either of those relays in the FSM. I may have yanked them as a matter of course, but can anyone tell me where to find them?

It's probably an old wire, probably exposed to the elements, but hopefully not in a bundle. Can anyone suggest any other things to check? Thanks.

the Other Matt

02-25-2007, 11:34 AM
Last time I had a drain problem in my Toy it was in the left tail light area. there was a bundle of wires and some became exposed due to rubbing. I do not know how much draw I had but after sitting for two three days the battery would be dead.

I cleaned the area up and covered the exposed wired and voila no more drain. I do not envy your situation, I HATE electrical work any kind. :mad:

Good luck to you, if you need to compare something let me know, I can check my truck. 90% of the wiring should be stock if not more.

02-25-2007, 12:24 PM
Thanks Tom,

It's an odd problem. I don't usually have a problem with electrical issues, but they way they put these trucks together is a nightmare. I did have a problem some time ago with the tail lights. One of the previous owners had done the poorest job I have ever seen in wiring up a trailer pigtail. I yanked that out at the last Cruise Moab in order to get the tail lights working again. (There were also the remnants of at least three alarm systems!)

You've got me thinking. Is the lead to the tail lights a hot which is grounded by the pedal (or the headlight)? Then a resistive short might actually effect it. I need to review the schematics. Also, I should recheck the tail lights themselves.

Thanks for the idea. I still need to figure out how to remove the stuck 80A fuse.

the Other Matt

02-25-2007, 03:58 PM
Like I said I am like water reacting with electricity so you don't want me to speculate on your questions.

I just know what was wrong with mine.

Your 4Runner sounds like my old one, I had three alarm systems in that thing before it got stolen:mad: Yours isn't red is it:thumb:

02-25-2007, 07:19 PM
White, not red. Whew. I examined the tail lights and measured the current flow with them disconnected. The brake light had around 0.3 Volts across it. Tracing it forward, I discovered a possible resistive short. When I taped that up, it cleared up that problem. I still measure a bit of current from the battery. I wonder what the time constant is for charging up the radio, clock, & computer, and so on. Thanks for the suggestion anyway. Let's see if this does the trick.

the Other Matt