01-19-2022, 06:21 PM
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#1
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Junior Member
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Join Date: Sep 2015
Location: Johnson City, TN
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Junior Member
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Location: Johnson City, TN
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Rear Defog - No power to fuse
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?
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01-19-2022, 06:29 PM
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#2
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Senior Member
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Join Date: Feb 2019
Location: Hot Springs, AR
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Real Name: Patrick
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Senior Member
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Quote:
Originally Posted by 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?
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What's your year and trim level?
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2000 SR5 V6 Manual 4WD https://www.toyota-4runner.org/3rd-g...biography.html
2000 Limited V6 Auto E-Locker Sold 3/2022
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01-19-2022, 06:44 PM
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#3
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Junior Member
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Join Date: Sep 2015
Location: Johnson City, TN
Posts: 21
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Junior Member
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Location: Johnson City, TN
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2000 Limited, e-locker
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01-19-2022, 08:14 PM
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#4
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Senior Member
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Join Date: Mar 2010
Location: denver
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Quote:
Originally Posted by 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?
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You are checking for power with ignition on?
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01-19-2022, 08:34 PM
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#5
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Join Date: Mar 2010
Location: denver
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Quote:
Originally Posted by 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?
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Attached is the defogger circuit. The body écu controls the defogger function when the ignition is on and the defogger switch is pushed.
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01-20-2022, 08:10 AM
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#6
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Junior Member
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Join Date: Sep 2015
Location: Johnson City, TN
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Quote:
Originally Posted by spartacus
You are checking for power with ignition on?
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Yes.
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01-20-2022, 12:01 PM
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#7
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Quote:
Originally Posted by spartacus
Attached is the defogger circuit. The body écu controls the defogger function when the ignition is on and the defogger switch is pushed.
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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.
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01-20-2022, 12:52 PM
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#8
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Senior Member
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Join Date: Feb 2019
Location: Hot Springs, AR
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Quote:
Originally Posted by john_brandon
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.
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What's your resistance reading between what should be the hot side of the fuse and the relay?
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01-20-2022, 01:05 PM
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#9
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Join Date: Mar 2010
Location: denver
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Quote:
Originally Posted by john_brandon
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.
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Enhanced pic
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01-20-2022, 03:23 PM
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#10
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Quote:
Originally Posted by Bad Luck
What's your resistance reading between what should be the hot side of the fuse and the relay?
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I get 13 at the R5 relay, 1 at the 15 amp rear defog fuse.
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01-26-2022, 10:35 AM
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#11
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Quote:
Originally Posted by Bad Luck
What's your resistance reading between what should be the hot side of the fuse and the relay?
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Any ideas?
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01-26-2022, 10:43 AM
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#12
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Senior Member
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Join Date: Feb 2019
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Real Name: Patrick
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Senior Member
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Quote:
Originally Posted by john_brandon
Any ideas?
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Quote:
Originally Posted by john_brandon
I get 13 at the R5 relay, 1 at the 15 amp rear defog fuse.
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The readings you posted make no sense to the question I asked so I have no ideas.
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01-26-2022, 12:45 PM
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#13
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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
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01-28-2022, 02:49 PM
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#14
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Quote:
Originally Posted by 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
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Quote:
Originally Posted by Bad Luck
The readings you posted make no sense to the question I asked so I have no ideas.
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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.
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01-28-2022, 06:03 PM
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#15
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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
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