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1997 Toyota T100
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Discussion Starter #1 (Edited)
Well, I think I finally caught the dreaded trailer harness adapter electrical gremlin. Dang it.

I thought my dash lights weren't working the other day, but it was bright and didn't check it later. But I went to drive my T100 this weekend on a trip, and I got down the road and noticed the dash lights were definitely not working. The dimmer had no effect.

Thanks to this wonderful forum, I remembered that trailer harnesses can cause all sorts of issues. So on a hunch at the gas station, I checked to see if my taillights were working.

They weren't. :frown: So I ran in a bought some new fuses for the taillights and dash lights to rule them out. New fuses had no effect. So I checked my adapter and the plug had a lot of water in it, and knowing that can cause issues, I got under the truck at the gas station and followed the trailer harness wires hoping that I could unplug it and that would fix the issue. Well, unfortunately there was no plug, and the PO had the harness wired in using Scotchlok connectors, all wrapped in tape. Well, I pulled all the harness wires out, and my my lights still didn't work. So back home we went, since it was getting dark, and we had to switch cars.

Everything was fine not long ago, and I towed my parent's trailer recently and everything went well...the trailer lights all worked correctly. So everything was fine recently.

So the harness is unplugged, but I haven't pulled all the Scotchlok connectors off yet. That may help, which I will do in a bit.

Is there anything else I could be missing, or any other suggestions? The only lights that don't work are my dash lights, license plate lights, and my running/driving lights.

The headlights, brake lights, and blinkers all work fine.
 

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1997 Toyota T100
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Discussion Starter #2 (Edited)
Update: Pulled the Scotchlock connectors off. Lights still aren't working. I know I could have some corrosion in my main harness, but the so far the wires appear to be in good shape, and the connectors didn't have any rust in them that I could see.

What am I missing? I know I also need to tape/seal up the wires that were used for the harness, but the lights should still work once the trailer harness is disconnected if that is the issue.
 

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1995 Toyota T100
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124 Posts
Probably a blown fuse in the box under the dash on the drivers side, located on the outside wall just above the foot rest, and caused by a short in the trailer wiring or the ground.

I learned the hard way.

Leon
 

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1998 T100 SR5 2WD
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13,580 Posts
Dimmer switch unplugged or bad?

Check fer voltage at the connector prior to where the Scotchlok connectors were.
 

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1996 T100 RegCab 2WD
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385 Posts
After my electrical ordeal, I'm a big fan of checking for a faulty ground. There are two on the driver's side and one on the passenger side in the cab. Unbolt them and hit the washer with a file/sandpaper to get any buildup or corrosion off.
Good luck on this issue. I absolutely HATE electrical problems!!
 

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1997 Toyota T100
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Discussion Starter #6
Probably a blown fuse in the box under the dash on the drivers side, located on the outside wall just above the foot rest, and caused by a short in the trailer wiring or the ground.

I learned the hard way.

Leon
Dimmer switch unplugged or bad?

Check fer voltage at the connector prior to where the Scotchlok connectors were.
After my electrical ordeal, I'm a big fan of checking for a faulty ground. There are two on the driver's side and one on the passenger side in the cab. Unbolt them and hit the washer with a file/sandpaper to get any buildup or corrosion off.
Good luck on this issue. I absolutely HATE electrical problems!!

I checked and replaced the fuses in the kick panel for the dash and tail lights, but not all of them. I will give them a once over again, though.


Dimmer was working just fine until all the dash lights went out. I will check to make sure it isn't unplugged, but that doesn't mean the dimmer didn't go bad all of a sudden. Voltage check both at the wires and before sounds like my next step.


I thought about the grounds, too. I will definitely check and clean to ensure that bad grounds are ruled out.


Also, does anyone know off-hand if there may be a relay that got tripped, and would unplugging the battery for a bit do anything to possibly reset it if there?
 

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1998 T100 SR5 2WD
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13,580 Posts
Looking over my EWD...guess what I find that powers instrument cluster lights as well as the license plate lights? The Tail Light Relay! ;)

It should be located behind the driver's side kick panel right off the fuse panel. It looks like it should be the round relay that located above the 15A Tail light fuse. It will have 3 lugs on the relay compared to the 4 lugs on the other relays. ;)

I don't think unplugging the battery will do anything to reset it. It might be worth yer time to unplug the relay, push it back in to see it will fix it or not. ;)
 

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1998 T100 SR5 2WD
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13,580 Posts
Here's the part number...
85916N RELAY, TAIL LAMP
90987-01003 1 $52.90

 

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1997 Toyota T100
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Discussion Starter #9
Awesome! Bam you are the man. Thanks so much for the info...it gives me something else to check. Maybe I just knocked it loose (hopefully).


Thanks again!
 

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1997 Toyota T100
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Discussion Starter #10
FIXED:


Well, I have to eat a little crow here. In my haste at the gas station the other night, I actually replaced the stoplight fuse, not the taillight fuse. I was in such a hurry to get back on the road and get to the beach for the weekend with the kayaks, I made a dumb mistake and mis-read the fuse panel labels.


So as I looked at the relay Bam noted last night, I decided to give the fuses a once over again. Well, guess which fuse was blown...yup, the taillight fuse.


Replaced it, and all was working well again. Dash lights, taillights, etc.


So just FYI - if you're in a hurry, take a deep breath and slowly go over what you're working on to make sure you're actually doing it correctly. Unlike me.


So to recap, the taillight fuse in the kick panel of a 1997 T100 4WD manual trans actually controls the taillights, the dash lights, the license plate lights, and the lights-on buzzer. It's a 15A fuse.


Thankfully it was a dumb mistake. All I have to do now is seal up the factory wire harness where the trailer harness had been spliced in. Then I'll need a new trailer harness.


Can anyone recommend a good one that plugs into something as opposed to needing to be spliced in?
 

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1998 T100 SR5 2WD
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I had a Hoppy branded one on my truck until the controller gave out. So I cut out the original controller and wired in a U-haul one. It still plugs into the wiring harness. :D
 

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Wire it in via solder and heat shrink. WHen not is use fab a mount so its upside down and OPEN (not with a cover on it like many have). Just leave it upside down and maybe dab a little electrical grease in there to fend corrosion.
 

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1997 Toyota T100
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Discussion Starter #14
I had a Hoppy branded one on my truck until the controller gave out. So I cut out the original controller and wired in a U-haul one. It still plugs into the wiring harness. :D

Thanks Bam, I'll take a look.

:grin::grin::grin::grin::grin:
Haha, yep.


Wire it in via solder and heat shrink. WHen not is use fab a mount so its upside down and OPEN (not with a cover on it like many have). Just leave it upside down and maybe dab a little electrical grease in there to fend corrosion.

Good idea if I can't find a plug-n-play unit to use.


Thanks!
 

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KS
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FIXED:


Well, I have to eat a little crow here. In my haste at the gas station the other night, I actually replaced the stoplight fuse, not the taillight fuse. I was in such a hurry to get back on the road and get to the beach for the weekend with the kayaks, I made a dumb mistake and mis-read the fuse panel labels.


So as I looked at the relay Bam noted last night, I decided to give the fuses a once over again. Well, guess which fuse was blown...yup, the taillight fuse.


Replaced it, and all was working well again. Dash lights, taillights, etc.


So just FYI - if you're in a hurry, take a deep breath and slowly go over what you're working on to make sure you're actually doing it correctly. Unlike me.


So to recap, the taillight fuse in the kick panel of a 1997 T100 4WD manual trans actually controls the taillights, the dash lights, the license plate lights, and the lights-on buzzer. It's a 15A fuse.


Thankfully it was a dumb mistake. All I have to do now is seal up the factory wire harness where the trailer harness had been spliced in. Then I'll need a new trailer harness.


Can anyone recommend a good one that plugs into something as opposed to needing to be spliced in?
Nice work SC! I too have come across this;) Thanks for posting up the results and how you fixed it. Electrical problems call always be fun...
 

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1997 Toyota T100
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Discussion Starter #16
Nice work SC! I too have come across this;) Thanks for posting up the results and how you fixed it. Electrical problems call always be fun...


Yeah...all but the most basic electrical stuff has always been hard for me. I'm just glad it was something simple (and dumb on my part) as opposed to something deeper and more difficult!
 

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1997 Toyota T100
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Discussion Starter #17
Update time! I finally got my new trailer harness installed this past weekend.I ordered the Hopkins #43355 plug-in trailer harness adapter...it ran about $45 from Amazon or so. No install pics (I'll try to remember to get pics of it all installed soon), but it plugged right in without issue. It seems like a high-quality unit. All the plugs were tight, and it comes with some seemingly heavy-duty weatherproofing on all the wires except for one. All lights work without issue, but I haven't plugged in a trailer yet. But overall, I'm back up and running!



 
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