Rear defrost fuse keeps popping...

[Bijan]

I have tried to find a short in my 2002 4Runner. If I turn the truck off, insert a new fuse in my “defog” slot under the hood, turn the key on, and press my defrost button - the fuse will blow instantly.

I pulled off the rear cargo panel to test the continuity and plugs for the rear window. All connections seem good.

I pulled off the rubber boot that’s in the hinge of the door. I found 5 frayed wires. Re-wired those. Fuse still blows.

I unplugged the two connectors from the rear window. Fuse still blows.

Thoughts on where to look next? Driver door jamb? Dash switch? :noidea:

 

[spartacus]

I have tried to find a short in my 2002 4Runner. If I turn the truck off, insert a new fuse in my “defog” slot under the hood, turn the key on, and press my defrost button - the fuse will blow instantly.

I pulled off the rear cargo panel to test the continuity and plugs for the rear window. All connections seem good.

I pulled off the rubber boot that’s in the hinge of the door. I found 5 frayed wires. Re-wired those. Fuse still blows.

I unplugged the two connectors from the rear window. Fuse still blows.

Thoughts on where to look next? Driver door jamb


If the switch circuit had a short then it will blow the fuse to the body ecu. the only way to detect short to ground in the black power wire is to check resistance from the fuse to the rear window and at all the connections inbetween. The defogger in the glass itself can also be a culprit but extremely rare.
Do you have access to the wiring diagram? if not I will post them when I get home this afternoon.

 

[TheDurk]

[MENTION=50279]spartacus[/MENTION] speaketh truth.

http://www.teamtoyota4x4.org/archivio/1996%20to%202002%20Toyota%204Runner%20Repair%20and%20Wiring%20Manuals/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/systemci/053rwdmh.pdf


Your mission is to open the BS1 connector inside the hatch on the left side. If it still blows the fuse. then work forward checking the black wire from that connector through the gate, the harness, and to the connector in the roof. (If you get there, open that one to see if you missed the fault or if it is further forward.) If no blow, fault is in the liftgate between the connector and the window. If you really can't find it, redneck fix is run a new wire alongside the old one.

BS1 is a two-row 10-pin dark grey wire-to-wire connector in the lower left hand corner of the liftgate.

 

[baja1]

the parasitic draw on my 2000 ended up being the rear window defogger....I didn't even know I had one!:shrug:

 

[Bijan]

[MENTION=50279]spartacus[/MENTION] speaketh truth.

http://www.teamtoyota4x4.org/archivio/1996%20to%202002%20Toyota%204Runner%20Repair%20and%20Wiring%20Manuals/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/systemci/053rwdmh.pdf


Your mission is to open the BS1 connector inside the hatch on the left side. If it still blows the fuse. then work forward checking the black wire from that connector through the gate, the harness, and to the connector in the roof. (If you get there, open that one to see if you missed the fault or if it is further forward.) If no blow, fault is in the liftgate between the connector and the window. If you really can't find it, redneck fix is run a new wire alongside the old one.

BS1 is a two-row 10-pin dark grey wire-to-wire connector in the lower left hand corner of the liftgate.

Thanks. Quick last question - is the Body ECU and BCM the same thing?
Located under the dash board fuse panel?

 

[TheDurk]

Thanks. Quick last question - is the Body ECU and BCM the same thing?
Located under the dash board fuse panel?

What's a BCM? If that is supposed to be Body Control Module, then BCM is the wrong name for the same thing. There is no Body Control Module in Toyotaspeak. There is only an Engine Control Module by the Glove box. See page 30.

http://www.teamtoyota4x4.org/archivio/1996%20to%202002%20Toyota%204Runner%20Repair%20and%20Wiring%20Manuals/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/electric/parts.pdf