The wiper motor isn't coming on, but shorting to the motor shows it works fine. I pulled the fuse for the wiper and the fuse for 4x4 right below it. I don't have a good wiring diagram.

| 1 | 2 |   Wiper fuse
| 3 | 4 |   4x4 fuse

With the wiper switch on high, reading from battery negative to: 1=~.5v, 2=floating, 3=~12v, 4=~12mv. Reading from battery positive to: 1=~11.5v, 2=floating 3=~12mv, 4=~12v

I think that indicates to me that the ground side of the lower fuse is #4, while the ground side of the wiper fuse is #1? And I would think then that I have a break in the circuit somewhere between the battery and #2? Would the steering column switch account for the .5 v drop? And then what would that make the .4v from 1 to 4?

I really want to test by just shoving a jumper wire between 3 and 1, but I want a second opinion before I fry something.

  • I don't think you'd have a specific ground from the fuse panel. If you pull a fuse, there are two sides. One side is going to be coming from the power source (whether switched or always on), while the other side is going out to the device it is powering. (This may be different for the lights, but not sure.) Each device will be grounded at its location or through a secondary ground wire coming from the device. The fuse box is a pass through for power with the fusible link put in place to kill that power incase of a short. Commented May 3, 2022 at 12:01
  • That's part of my question. The simple diagram I have seems to show that the fuse panel is before the switch, so power coming in whether it's one big line powering the entire fuse panel, or one per fuse, and then one "ground" out of the panel to whatever is next in line (which I guess would be multi-function switch [MFS] and then wiper motor and then ground). I would think that even with the MFS off, I would be able to get +12 from whichever side of the wiper fuse is + to the negative side of the 4x4 switch, but I'm not.
    – user34314
    Commented May 3, 2022 at 17:35
  • Was the power turned on via ignition? If this is switched power, you wouldn't see it there with the ignition switch in the off position. Might pick up power from ACC position (wiper might, but I doubt 4x4 would). Commented May 3, 2022 at 18:21
  • Power was on and the MFS was in high. I even tested the rear wiper to be sure, and it worked (although I can't find the fuse for it at all?) I also retested the -11.5 I'm getting, and that doesn't change with the switch on or off, so I must be wrong about that being the line to the switch.
    – user34314
    Commented May 4, 2022 at 9:28

2 Answers 2


Check the wiper relay output, in addition to any obvious signs of wiring damage. Here's the wiring diagram for the '99 4Runner.enter image description here

I haven't looked at how it's built myself but if there are no pin numbers and it's drawn as one block - chances are the relay is built in. Check the voltage on the pin 17 of the switch as that's the main power. Then check the voltage at the fuse (take it out, one end should be at 12V when the ignition is at ACC position, against a proven ground point). If there isn't 12V there - run a wire (with a fuse) from the battery to that fuse to see if the wiper motor is operating now. If it does - it's the power to the fuse that's damaged. If it doesn't - have to keep looking, tracing all the points after the fuse.

  • 1
    By the wiring diagram, the wiper relay is only used for intermittent mode, not the high or low setting. The diagram will be useful however.
    – HandyHowie
    Commented May 4, 2022 at 6:41
  • It's definitely better than I've got, but i'm having a hard time tying it to the physical in my mind (I'm trying my best not to take the dash and fuse panel apart yet). What is the gray box in the middle? Just a junction? What's 3a? And are the numbers pin numbers? Is the b-y wire going into the fuse panel one big wire for everything, or just one wire going to those two fuses? (And actually just one fuse in america, right?)
    – user34314
    Commented May 4, 2022 at 9:50
  • It looks like for an american 4runner, assuming the central 4-way thing is just a junction, that power will flow through the fuse and into the relay regardless of the position of the wiper switch. Would this account for me seeing 11.5 volts between 4x4 fuse positive and wiper fuse assumed negative regardless of what position the wiper switch is in? Maybe grounding through the relay with minimal current or something even when the relay is "off"?
    – user34314
    Commented May 4, 2022 at 20:01
  • The small numbers by each connection are the pin numbers on the corresponding connector. I would assume B-Y wire is common power to a lot of stuff in the fuse box. @HandyHowie is correct, looks like the motor is operated by the swich directly if not in intermittent mode, so start by checking the outputs there.
    – EᑎOT
    Commented May 4, 2022 at 22:39
  • Yeah, and looks like "Connector 3A at the junction block near the steering column tube under the dash".
    – EᑎOT
    Commented May 4, 2022 at 22:43

Ultimately, this ended up being the issue. The fuses in the panel are arranged as if the sticker on the door is correct when the door is installed. lines indicate incorrect reversed fuses.  This is NOT how they are supposed to be installed<lines indicate incorrect reversed fuses. This is NOT how they are supposed to be installed>

And it seems to make sense based on number of fuses and is only off by the top left fuse being 20A instead of 30A. I can't make it out well enough right now, but I'm betting the big "fusible link" or whatever it is is 30A, and that the 20A is either not really active, or is something else, like the fuse I haven't been able to find for the rear wiper.

Regardless, I found out when I tried to start the car with the "wiper" fuse out that the 20A wiper fuse is actually the position for the starter relay. The 7.5A fuse is in the actual wiper fuse position and was blown. I guess that explains why the starter kicked in when I shorted the fuse during testing. (My wife said this all started when she was cleaning the ice off her windshield. She said she moved it by hand and thought she broke something, but I bet that she had the wipers on; I bet that the 7.5A fuse is enough when the motor is free, but not when the wiper blades are frozen down.)

I verified that the wiper, starter, and stop fuses are all reversed, and I imagine everything else in there is reversed as well. I swapped the lower four fuses, replaced the blown 7.5, and everything's good to go. Now I just need to swap all of the others around.

  • This is likely a lid from either the Japanese version (Surf) or some other Toyota vehicle alltogether.
    – EᑎOT
    Commented May 17, 2022 at 23:31
  • Maybe. I figure it's more likely that it's just a bad diagram (putting the 30A fusible link in the same grid), the fuses are SUPPOSED to be installed in the same order as the diagram when you're looking at it, and someone just got confused and installed all of the fuses backward at some point in the past. That doesn't explain that extra 20A, though. I pulled it out, and it's not the rear wiper. I didn't check whether it really has any power, though.
    – user34314
    Commented May 18, 2022 at 3:15
  • I took a look at the diagram on my '99 4Runner and yes, you appear to be correct. I have exactly the same diagram on my North American 4Runner.
    – EᑎOT
    Commented May 19, 2022 at 16:49

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