00 4RUNNER 4X4 3.4L

The fuse (15a) to the rear window defogger keeps blowing out everytime i put in a new fuse by turning on the defogger. Any ideas?.....

 

you have a short somewhere in the wiring that it causing it to ground out.
Fuse is doing it's job by blowing. I think someone on this forum had a similar issue and his truck burned up.

Start at the console and than at the rear of the truck, after 15 years a wire may have become worn or a connection is loose.

 

Thank u sure will check it out this weekend.

 

A good place to start because it's super quick, easy and common is the wiring under the rubber boot between the hatch and the body. It's on an off chance, be hard to ground out there, I suppose, though multiple wires often break.

 

X2 on this.

 

i'LL check it out when i get a chance this weekend...its irritating when the rear window is foggy or icy smh

 

Bump...

So I checked behind the middle console, checked the rear hatch for the two wires both are connected and checked the wires no fray at all. Put another fuse in press the switch bam! blew the 15a fuse again. Im beginning to think its the defogger switch itself. Is it so??? lmk what u guys think.

 

It could be but I would think a short in the hatch is more likely.

 

Actually, there is zero chance the switch is the culprit. If that switch circuit shorts to ground, it will blow a fuse that supplies the Body ECU, not the 15A DEFOG fuse which is NOT part of the button circuit. The 15A DEFOG fuse blowing means you have a short to ground in the black wire from the fuse to the rear window, or a defect internal to the glass itself. End of story, and the switch is not part of it. See attached.

Pick one end of that black wire, and measure resistance to ground at each connection along its length, heading towards the other end.

Me, I agree the liftgate harness at the flex is the most likely point of failure. Make sure you check just INSIDE both the hatch and body. Second is a loose black hot wire inside the liftgate.

 

Sorry for resurrecting this thread, but I had the exact same issue and found this thread. I also have resolved the issue and wanted to share.

I found the typical wire breakage and exposed wires at the top of the hatch door and fixed three wires there, but fuses were still blowing as soon as I turned on the rear defroster.

I finally got to testing continuity on the wires from the defroster tabs back to the rear control box connectors and low and behold found the two wires were shorting to each other. I ended up pulling the wires off of several mount points (major pita!) and out of the door in order to troubleshoot. I found two places where the brittle insulation had cracked and the exposed wires were touching. It looks like cycling the back window up and down over the years along with the wire insulation aging and getting brittle caused the wires to crack where they bend and cause shorts. After fixing the wire, watched the wires as I put the window up and down and figured out where to best zip tie the wires back in place and still allow the wire to travel with the window without hanging up or bending sharply.

Anyway, I hope this helps anyone else that has had to deal with this frustration.