Rear Defog - No power to fuse

[john_brandon]

Been searching high and low for this. My rear defogger is not working. I checked everything (pulled rear door trim, checked for frayed wires at the top of the door, you name it) to find that when the defog is activated there is not power at the fuse under the hood. I checked the mirror heater and it gets a reading. I've pulled diagram after diagram, switched a known good relay from R3, R6 to R5, still nothing. Any suggestions?

 

[Bad Luck]

Been searching high and low for this. My rear defogger is not working. I checked everything (pulled rear door trim, checked for frayed wires at the top of the door, you name it) to find that when the defog is activated there is not power at the fuse under the hood. I checked the mirror heater and it gets a reading. I've pulled diagram after diagram, switched a known good relay from R3, R6 to R5, still nothing. Any suggestions?

What's your year and trim level?

 

[john_brandon]

2000 Limited, e-locker

 

[spartacus]

Been searching high and low for this. My rear defogger is not working. I checked everything (pulled rear door trim, checked for frayed wires at the top of the door, you name it) to find that when the defog is activated there is not power at the fuse under the hood. I checked the mirror heater and it gets a reading. I've pulled diagram after diagram, switched a known good relay from R3, R6 to R5, still nothing. Any suggestions?

You are checking for power with ignition on?

 

[spartacus]

Been searching high and low for this. My rear defogger is not working. I checked everything (pulled rear door trim, checked for frayed wires at the top of the door, you name it) to find that when the defog is activated there is not power at the fuse under the hood. I checked the mirror heater and it gets a reading. I've pulled diagram after diagram, switched a known good relay from R3, R6 to R5, still nothing. Any suggestions?

Attached is the defogger circuit. The body écu controls the defogger function when the ignition is on and the defogger switch is pushed.

 

[john_brandon]

You are checking for power with ignition on?

Yes.

 

[john_brandon]

Attached is the defogger circuit. The body écu controls the defogger function when the ignition is on and the defogger switch is pushed.

Thanks! Very helpful. With the truck running I push the center console button, it lights up and the mirror heaters are activated and working. I'm not able read the areas circled in yellow to verify relays.

I used this Toyota 4Runner (1999-2002) Fuse Diagram • FuseCheck.com to check anything related to rear defog. No problems with anything else. Door locks, rear window and wiper, horn, open door warning all work fine.

 

[Bad Luck]

Thanks! Very helpful. With the truck running I push the center console button, it lights up and the mirror heaters are activated and working. I'm not able read the areas circled in yellow to verify relays.

I used this Toyota 4Runner (1999-2002) Fuse Diagram • FuseCheck.com to check anything related to rear defog. No problems with anything else. Door locks, rear window and wiper, horn, open door warning all work fine.

What's your resistance reading between what should be the hot side of the fuse and the relay?

 

[spartacus]

Thanks! Very helpful. With the truck running I push the center console button, it lights up and the mirror heaters are activated and working. I'm not able read the areas circled in yellow to verify relays.

I used this Toyota 4Runner (1999-2002) Fuse Diagram • FuseCheck.com to check anything related to rear defog. No problems with anything else. Door locks, rear window and wiper, horn, open door warning all work fine.

Enhanced pic

 

[john_brandon]

What's your resistance reading between what should be the hot side of the fuse and the relay?

I get 13 at the R5 relay, 1 at the 15 amp rear defog fuse.

 

[john_brandon]

What's your resistance reading between what should be the hot side of the fuse and the relay?

Any ideas?

 

[Bad Luck]

Any ideas?

I get 13 at the R5 relay, 1 at the 15 amp rear defog fuse.

The readings you posted make no sense to the question I asked so I have no ideas.

 

[jbtvt]

If you mean 13 ohms that would be very high for a run of wiring, so double check that you're measuring correctly and check for corrosion on terminals. Based on what you've said with having a good relay and continuity between relay and fuse, high resistance aside, you should either have no power at female relay terminals 1 and/or 5, or no continuity on black/orange wire between relay and ecu, grounding your relay coil. It might help to watch a video explaining how relays work if you need clarification on that

 

[john_brandon]

If you mean 13 ohms that would be very high for a run of wiring, so double check that you're measuring correctly and check for corrosion on terminals. Based on what you've said with having a good relay and continuity between relay and fuse, high resistance aside, you should either have no power at female relay terminals 1 and/or 5, or no continuity on black/orange wire between relay and ecu, grounding your relay coil. It might help to watch a video explaining how relays work if you need clarification on that

The readings you posted make no sense to the question I asked so I have no ideas.

Obviously a rook at using a multimeter but I got -2.45 ohms from relay terminal 3 to fuse. That doesn't seem to make sense to me?! Below is link to a pic of the reading. I have no power at terminal 1 or 5, no continuity terminal 2/black and orange wire.


Microsoft OneDrive - Access files anywhere. Create docs with free Office Online.

 

[jbtvt]

Thought they had a transistor test selector in the middle of ohms at first glance but I guess that's 20k. Never really looked at the layout. You want to be in the lowest range you can get a reading in which should be 200 but it shouldn't be negative so not sure what's going on with that. Some of the other HF meters are decent but maybe that one is not.

Wait I just reread your first post. You have power at the mirror heater fuse? Because if that diagram is correct they come from the same relay, the only difference being a splice, possibly under the fuse box. So I don't know how you could have power at either without power at relay terminals 1 and 5, seems like you're either testing the wrong terminals or need a new meter. 1997 didn't have multiplex but didn't have heated mirrors either so that's not much help, don't know which you'd have in 00

If you actually have power at the mirror relay but not the defog relay, and that first diagram is the right one, then the problem is in the small run of wire after they split but before the fuse