Diagnose- dash, tail, and brake lights failing

[Dingoboy]

Hey guys,

I just got my Supra back from the shop 2 days ago after having a number of things done. Most notable was a swap from hydro fan to Flex-A-Lites on my 1JZ engine. Most of the A/C system was also replaced. So the mechanic was in the fuse panels as well as behind the glove box near the ECU.

As I got home the other night, it was getting dark, so I flipped on the headlights. They worked fine, but no interior illumination of any kind was working. I also noticed that it seemed like my brake lights weren't working- no red glow on the front of the car that stopped 6 inches from my bumper. And when I got home, I also confirmed no running lights.

I can't get to diagnosing this until Saturday at the earliest, and I am a little impatient with electrical gremlins. I figure the first place to check is the fuse panel- it seems that the dash, tails, and brake lights have separate fuses, so I don't really expect to find the issue there.

Looking at the TSRM, the only common recommendation for all 3 appears to be to check ground. Do these 3 systems share a common ground? If so, where should I direct my attention/search?

Thanks in advance for any help. And yes- I did try searching, but found nothing on the ground info that was noted to be specifically for the tail lights. And no mention of all 3 of these items going out at once. I'll keep trying between now & Saturday, but appreciate any clues from those in the know.

 

[ForcedTorque]

I can't remember what all it kills, but not having your emergency flasher switch plugged in does a lot of this. It's the easiest possible fix as well. Check that first. A shop forgetting to plug up a plug wouldn't surprise me.

 

[Dingoboy]

Interesting- I'll put that on the troubleshooting list. Thanks! I'd never have thought of that.

 

[shaeff]

When the hazard switch is unplugged, your running lights, and dash lights will come on at the second click, but when the headlights come on at the third click, the headlights will turn on but the others lights will go out.

 

[Jimbo]

I had that problem, turned out to be one of the gray relays in the fuse panel next to the pedals. forgot which one it was exactly, check the TSRM. it shouldn't be the hazard switch. mine is unplugged right now since Im changing the cluster light bulbs, and all the other lights turn on fine.

 

[Dingoboy]

Appreciate the extra info. More ammo before I start troubleshooting tomorrow afternoon. I'll let you guys know what I find, if anything.

 

[Dingoboy]

OK, so the hazard light switch is plugged in- flipped it on & the hazards flashed. Turn signals also work properly.

Checked the fuses for tails, stop, and gauges, all on the top row of the kick panel fuse box. All tested good both visually and with a proper fuse tester.

I see the taillight relay just above those fuses on the right (towards the front of the car). Doesn't seem to want to come out easily, afraid to just yank on the sucker. Can anyone confirm it just pulls straight out? And would that relay stop the gauges & brake lights from working, in addition to the tails? If I yank it out, is there a proper method for testing it? (Never have tried testing a relay.) If not, I can just buy a new one from Toyota, but I'd rather not, y'know? Not without being fairly sure that's the problem.

Also- do all of these systems (gauges, tails, brake lights) share a common ground anywhere? If so, does anyone have a good idea of where that ought to be?

I'm going to go back out & keep toiling. I still have to figure out why my outside mirrors don't move, but the switch makes all the lights (gauges, headlights, etc.) dim & the voltmeter drops to about 8v. This problem predated the current lighting issues, so I don't expect they are related, but I wouldn't be entirely shocked if they are. Guy before me did a shade tree wiring job for his stereo, which appears to have been yanked in a hurry before he sold the car.

Fun fact: I found a momentary toggle switch drilled into the driver's side kick panel near the fuses. I have no idea what use a momentary toggle would be down there, and I haven't yet tried to trace the wiring- it just seems to go up above the fuse panel & disappear. I have a feeling I'm eventually going to be pulling the entire dash out of this car & trying to clean up the rat's nest wiring job. Just not soon, as I don't have the time for it now.

 

[mkiiichip]

Do you have battery voltage at the fuses in question?

 

[Dingoboy]

Do you have battery voltage at the fuses in question?

Of that I am uncertain. Not sure I can contort myself in there to check it, but I will try. Probably tomorrow, as I am about to head out for dinner with friends.

Just so I know where you're going with this- no voltage = relay issue?

 

[mkiiichip]

lol yeah. no voltage no worky
the circut is super easy to follow here,
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=D&P=3
at the top of the page there is a circut labeled "A" (just keep going page to page its always at the top), it provides the power for all the circuits you are having an issue with. Start at the battery and keep checking all the circuits until you find where the voltage stops.

G/L

EDIT: no not a relay issue

 

[Jimbo]

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=BE&P=13

Check relay B. It should pull right out, if theres even one there

 

[Dingoboy]

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=BE&P=13

Check relay B. It should pull right out, if theres even one there

That's the one I was trying to yank... doesn't seem to wanna let go, so I didn't want to push my luck. I'll give it a go with a bit more gusto later. I have problems in 2 different spots in my back, and a surgically repaired right shoulder, so getting twisted around to where I can see the fuse panel & also get a grip on anything in there is kind of a chore.

 

[Dingoboy]

I can't seem to contort myself into a position where I can get test leads into the fuse block. So I tried checking the dimmer switch with a multimeter, which I was told on another forum could also be the issue. I have continuity across the poles on the back of the dimmer switch, so that doesn't seem to be the culprit. But when I turn on the lights & press my leads into the wiring harness connector where the power should be, I get nothing. (I tried across the power leads, and also from each power lead (not knowing which was in or out) to the ground- no dice.)

Forgive my ignorance, but am I correct in assuming that the ground in the back of the switch (wiring harness) provides ground ONLY for the switch? Because that appears to be a good ground. But if I am not getting power at the switch, I am thinking it is either faulty relay (gawd help me on that one) or a bad ground elsewhere in the loop. Any idea where I should check for a ground that would affect gauge/dash lights, fogs, tails, and brake lights, but nothing else? (Or at least nothing I've yet noticed)

I'm going to put on some shorts, go outside, and see if I can twist my body into a shape & position that will let me get a good look at the fuse panel & relays. I may never get back out of there, but I'ma try... say a prayer for me, my arthritic back & neck & surgically repaired shoulder. LOL

 

[ForcedTorque]

I've got 4 bulging discs in my neck (for the last 15 years), so I somewhat know what you are talking about. One thing you could think about, is that the seat only has 4 bolts. Then, you could almost lay flat, and hell, you may get "paid" for pulling it. It's an extra 10-15 (or 2-3) minutes for some comfort.

 

[Dingoboy]

I thought about yanking the seat, actually, yeah.

I went ahead & pulled the lower dash cover & such, and I am finding more and more surprises as I go. Vacuum lines- some open, some not. Stray wires with varying amounts of electrial tape on them. And in the melange of wiring that lies just rear of the fuse panel, every time I move the mass of wires, there is a relay that clicks, but I'l be damned if I can figure out which one it is. Or which specific wire is causing it to click over. (This is with no key in the ignition)

So I am calling in the cavalry. My best friend, who used to work on my '90 Supra with me, is now a professional mechanic. (Back then, I was the more accomplished mechanic... not no mo') And he has always had a gift for electrical troubleshooting- he started electrical/electronics before he started learning auto mechanics. But he lives in Houston now. Still, for the price of 4 hours of mechanical labor, I can fly him in for the weekend & we'll troubleshoot, hang out, enjoy a few adult beverages, etc., etc. and it'll be worth FAR more than the cost of the plane ticket.

Barring spousal objections on his end, this should happen next weekend. Fingers crossed.

 

[Dingoboy]

Wow... airfare from Houston to Tampa is sky high for a "last minute" flight. Pun intended. So this may not happen for a while, unless there are some "seriously last minute" discounts available later in the week. Dangit.

Any more advice/pointers from the community are welcomed. Today, I think I will stick to swapping in USDM tails & cleaning up/photographing/boxing up my JDM tails for future sale.

If I have time left after that, I may explore installing my NashMan shifter kit.

If by some miracle, I get that done & have time left, I will crawl back under the dash for some quality time with the wiring explosion.

 

[Dingoboy]

My buddy ended up here this weekend, and while the lighting issue is now fixed, I am perplexed. As was he. Even after the fix, we're scratching our heads.

He found no power to the taillight fuse under the dash. He did jumper another power source to that slot just to test continuity & ground to the lights, and everything worked. Eventually narrowed it down to the power between the 100A alternator fuse & the interior fuse panel. Had to pull the engine bay fuse box & then start ripping electrical tape off the wire bundles heading back along the driver's side of the engine bay.

Here's what confused us both. He exposed a pair of severed 10-12 gauge wires in black sheath near the PS reservoir that looked a lot like the power lines coming off the 100A alternator fuse. But they were severed. AND they were in ONE sheath, running parallel to one another, much like speaker wire. Oddly, one of the wires had power, while the other tested positive for continuity to the taillight fuse in the kick panel. And when jumpered together, the darned lights came back to life- fogs, gauges, tails, brakes, side markers, everything.

Why would power be fed up one side of 2 wires in a sheath & back down the other side? Is it possible I am missing a relay or some sort of odd in-line fuse there? With everything working properly now, I'm pretty happy, but I wonder if I am sitting on a new problem waiting to happen.

On top of that, the wires in question were wrapped in electrical tape that did NOT look new, and they appeared to have been severed for a long time- this problem only dates back a few weeks to when my mechanic installed the fans. Which means that maybe this circuit was previously being fed from somewhere else? And if so, why? Was there something wrong with this wiring? I'm just hoping I don't wake up to an electrical fire in my garage. LOL

 

[trd0629]

you know i have the same wires too im going to try and connect them together thanx hopefully thats my problem