I need help with a weird electrical problem! *SOLVED*

Ok, so last night I was driving and noticed that, occasionally, when I hit the brake pedal, the back lighting for my gauges, and the back lighting for the climate control, basically anything controlled by the dimmer knob, would flick off for a second and then come back on. It didn't happen over bumps in the road or anything, only when I pushed the brake pedal, so I believe it's something to do with the brake light circuit. Anyway, so later on, they went off completely and never came back on. Then when I went to get out of my car, I noticed my power door locks no longer work either.

I tried looking through wiring diagrams, but I can't find the back lighting in any of them. I tried to see what the brake lights and door locks had in common, but the only thing I could find was they use the same ground. I checked that ground and it's clean with no corrosion or anything. I cleaned it anyway for just good measure but no luck. Any help is greatly appreciated! thanks

the car is an 88 alltrac btw

hmm, didn't know this before, but I guess my taillights and brake lights don't work at all either... which means I can't really safely drive the car until I fix this. I was looking through the wiring diagrams again, it turns out they all have the same power source (the wire marked B in the diagrams) I traced the wire back in the diagram to the battery, it goes through the 100A alternator fuse. My question is, where exactly is this wire? I believe it may be disconnected or something

Check your brake/tails fuse first. If it's not the fuse, this thread about brake/taillight short circuit may help:

Full thread:
http://alltrac.net/phpBB2/viewtopic.php ... ake+lights

Cliff notes:

Rick89GTS":2gn1bj1m said:

Solution found:
One of the contacts in the socket casing had melted down, creating a short circuit. I spliced in a good one from the wreckers and all is well again. Check all your bulb sockets first, it might save you a lot of work. A malfunctioning brake light switch won't cause your fuse to blow, a short will.

Click to expand...

well, I haven't really had any time to crawl under the dash to check the fuses, but the sockets for the tail and brake light bulbs all looked good, no shorts or corrosion in them at all.

however, it seems unlikely that the taillight, stop light, door lock, and gauge fuses would all blow simultaneously. I checked the 100A alternator fuse through which they all get their power and it looks fine. And the car still charges fine. actually, for a short time of about 15 minutes, the car was getting as high as 14.2V, which is the highest I've ever seen it! it normally sits around 13.0-13.4. So, that may be another clue but I'm not really sure what it means.

well, I have an update... but the results are making me confused even more...

Basically, I went to check my fuses, and I look at the first row, in positions 1, 2, 3, and 4. Positions 3 and 4 are the 15A tail and 15A stop light fuses. Position 1 is the 15A gauge fuse. In position 2 there was a piece of plastic which had legs like a fuse, which I'm guessing was to plug an un-used slot. I have two other plugs like this in 2 other un-used slots in this fuse block too. My BGB doesn't give a listing for anything in slot 2 so I figured it was unused. Now, I checked the gauge, tail, and stop fuses and all checked out good. Then I used a test light and checked for power at the fuse terminals. Slot 1 had power (I mistakingly thought that the gauge back lighting got power from this fuse, it actually gets it from the tail fuse) but slots 3 and 4 had no power... Now, out of curiosity, I checked for power in slot 2, which should be an unsed slot... but I found power! I grab a spare fuse and stick it in the slot, and just like that, slots 3 and 4 now also have power! and my door locks, taillights, brake lights, and everything begin to work again!

I suppose I should be happy that everything works but I really want to know where slot 2 draws power from and how it's connected to slots 3 and 4. Also, how could everything have worked before and suddenly stopped working but this fixes it? For all I know, I lost power for slots 3 and 4 due to an open circuit, and somehow by placing a fuse in slot 2, I simply connected them to a different power source, which wouldn't be good for the components that draw power from that circuit.

so basically, does anyone know what slot 2 is?

I am having the EXACT same problem and I just posted about it... I have an 88' as well. Any progess on your situation? I tore through my car this evening and have made absolutely no progress... I'll try the fuse in slot 2 and see it that fixes things... If it does, I would be very curious why.

Edit: I tried your fix and it works... But why??? This makes no sense at all. I've been looking over the schematics all night and cannot see why this would work... I wonder if it is possible if slot 2 is on the same circuit as 3/4 but just left open since it wasn't needed? I wonder if there is something wrong with the connectors going into the fuse box and a fuse in slot 2 bridges that gap? If true, I would assume a 30amp fuse would work since the other two are 15. I'll ask one of my friends who knows Toyotas really well and see if he knows any other cars around the same year that might use slot 2. At the very least, that might be a way to figure out what circuit it is likely on.

I think this post should get a sticky since it seems like there are quite a few people that have had this same problem. I'll keep working on it on my end and let you know if I find anything. This is great someone else is having the same problem at the same time...

Do you have a turbo timer?

I have made some progress, but not much. and yes, I have a turbo timer

Ok, what I've found is, the "B" power wire is definately the issue. I have power at the heater circuit breaker on the passenger side kick panel, but I do not have any power to the defroster circuit breaker on the driver's side kick panel. I first thought that the problem wire would run between the two fuse boxes, but I later realized from the diagrams, it looks like the B power wire must split into two wires, one going to the passenger kick panel to fuse box no. 4, the other going to fuse box no. 2 in the engine bay and then onto fuse box no. 1 in the driver's kick panel. So, the issue wire is somewhere between the engine bay fuse box and the driver's side kick panel. And the issue wire is a solid white wire, and I would assume it'd be a thicker gauge wire, like a 10 or 12 ga.

That's all I came up with last night, but I hope to look into it more this weekend.





Also, do NOT use a 30A fuse. Amperage stays the same throughout a circuit so just because you have 2 15A circuits does not mean you double the amperage of a fuse going to both. I put a 7.5A in just to be extra safe because I don't know if I piggybacked off another circuit with a lower amperage.

Weird and confusing.
I know non-sensical electrical problems can often be solved by cleaning or swapping in a newer fuse box. That usually indicates corrosion, resistance build up or just poor continuity after 20+ years. IIRC, someone cleaned out the connections underneath their fuse box and that solved the problem.
Just something to keep in mind.

I played around with it a little this morning and figured some stuff out... I agree with you that it could be the wire you are talking about. That, or a bad ground.

I put a 10amp fuse in slot 2 and decided to slowly ramp up and see what that circuit might be connected to. Everything will work fine (so it seems) with a 20amp fuse in slot 2 until you have your lights on, the rear defroster, and then the brakes. This combination will cause the the 25amp dome fuse in the engine bay to blow. Using slot 2 seems to be a (temporary) work around just as long as you don't use your rear defroster. I don't think anything it can effect is that horrible in terms of the other more sensitive electronics... I'm going to drive it like this for a while and just keep a bag of fuses with me.

Tomorrow I think I'm going to check and clean every ground I can find and see if that solves the problem. It has been raining here a lot and my car leaks so water might be part of the problem.

I'd say the biggest suspect will be corrosion, or loose terminals. I'm just saying that that one wire will be the suspect, it could be loose or corroded at either end, or it could be frayed or disconnected completely.

anyway, I'd be very interested to read the other threads where people are having problems with this. Do either of you have some links to them?

also, why did you ask if I had a turbo timer?

6strngs":1qex4bs9 said:

I'd say the biggest suspect will be corrosion, or loose terminals.....anyway, I'd be very interested to read the other threads where people are having problems with this. Do either of you have some links to them?....

Click to expand...

Not at the moment, might try a search on fuse box or something like that. I'll see if I can locate that post I was referring to...

no real update other than the fact that I've been searching this site for the last hour and a half and have found a handful of people who have had this same problem. no real resolutions from any of them though! argh! it's so frustrating when people post, say they have a problem, somebody gives a suggestion, but they never come back to say what the problem ended up being.

I did find a couple though. One guy simply said the problem was "the plug at the bottom of the engine bay fuse box" nothing about what was wrong with it though. Another guy said he took it to a toyota dealer who fixed it and told him he had a loose wire at his driver's kick panel fuse box.

I don't have school tomorrow, so I intend to re-install my fuse box which i had almost completely removed in the hopes to figure out what slot 2 actually was. I'm certain the problem can be fixed much easier than ripping the whole fuse box out though. So I'll update tomorrow with what I find.

Major update!!! I have solved it! Took me about 2 hours, but I found it. I got everything back together and still, nothing worked. I jiggled the wires in the kick panel and nothing, then I started jiggling the wires by the fuse box in the engine bay, and finally, everything started working again! I jiggled and jiggled and jiggled, and they stopped, and started several times until I found the one wire causing the problem. I know this is the problem for sure since, if I disconnect it, they'll stop working, and when I reconnect it, they start working again.

Basically, on the underside of the fuse box, there is a connector with a single white wire going to it. I struggled and struggled trying to get it out, it was stuck! then I realized it was stuck because it had melted into the fuse box. I had to break pieces of plastic off to get it out, but finally I did. it was definately corroded and melted and all-around bad. Here's a pic of my fuse box:


and here's a pic of the connector that is bad:



The easy solution would be to get a crimp connector from radioshack or something, and just connect that to it. otherwise, I'll need a new fuse box and connector. I'm going to look in a junkyard for a 3sfe fuse box (I'm pretty sure it's the GT that uses the same fusebox as the 3sgte, I should double check that though)

So, anyway, hopefully those of you who also have this problem will find this info useful in finding your own cause of this problem.

Nice! I was thinking that it could be the problem, but I saw Rick already suggested it, so I didn't bother. Mine was melted when I bought the car, and the previous owner put a new length of wire with a spade connector on it. Recently I completed a rebuild so I refurbished the entire harness, including bumping up the gauge on those wires. If I remember correctly that wire jumps to power from the alternator. tightening up/replacing all the connectors in the fuse box solved a lot of stupid little electrical issues I was having including hot no-starts, and blinking climate control lights when the turn signals are going.

20-year-old fuse box :doh:
What would cause it to melt that badly?!

Rick89GTS":2q78g5ga said:

20-year-old fuse box :doh:
What would cause it to melt that badly?!

Click to expand...

20 years of ST165 underhood temps.....

^Hehe, of course.
I found one of those links I was talking about.
Has some useful info, worth a look:

http://alltrac.net/phpBB2/viewtopic.php?p=102582#102582

Yeah, I saw that thread during my search yesterday. BTW, thanks for the help guys!

You've got to be kidding me! Nice work! I remember seeing a wire that looked just like that when I pulled my motor. I'll check mine this afternoon! That's awesome you found it. I was in the process of removing my dash to find and check all the grounds.

This deserves a sticky for sure!



Edit: Update! Yep, that fixed the problem. I think a good place to start for future electrical problems will be that fuse box.