Electrical Short = Pain

[mastacox]

Just allow me to say:

Hunting down a short behind the dash sucks. A lot. :( I don't suppose anyone knows where I can find the FSM for a '92 4Runner online do you? I need to figure out what wire is having a problem now, as I got the short sorted out, but none of my dash lights turn on with the headlights...

I guess looking on the bright side, with everything apart I will be able to easily clean up my wiring for all of the extra stuff I have added in :shake:

http://i93.photobucket.com/albums/l70/mastacox/92%204Runner%20Pics/IMG_2480.jpg

http://i93.photobucket.com/albums/l70/mastacox/92%204Runner%20Pics/IMG_2479.jpg

[Robinhood4x4]

Well there's your problem...!

I assume you found the FSM sticky?

[MTL_4runner]

Wow, look at all that spaghetti! :D

I assume you're well into that FSM by now.
What is the short are you looking for?

[4runnerchevy]

If your like me, I take apart the dash so can find the short under the hood. It ends up never where you look for it! :smokin:

[mastacox]

Thanks for the replies and links guys. I'm still trying to decide if I should put everything back together yet since things aren't quite working; I nearly had to unplug EVERYTHING to get to the harness where I needed to (main body harness directly under the windshield) and it ended up being easiest to just say screw it and remove the WHOLE dash. Kind of scary, but has made the electrical work a million times easier. This did give me the chance to buy a cool little Radio Shack butane-powered soldering iron, which works absolutely beautifully. Here's a link to the iron: Butane Soldering Iron (http://www.radioshack.com/product/index.jsp?productId=2062753&cp=&sr=1&origkw=butane+soldering+iron&kw=butane+soldering+iron&parentPage=search). I briefly considered the "Cold Heat" solderer but decided against it after hearing mostly negative reviews on it from electrical engineer co-workers.

The main short seems to have originated near the cigarette lighter plug; four wires on a plug there seem to have gotten warm, melted together, and then caused mass havoc (possibly due to me pulling power for the CB through the cig lighter circuit, but the CB was off and it hasn't posed a problem for a few years now). Two of the shorted wires literally melted/burned all of their insulation off up to the main wiring harness under the windshield, while the two others got warm enough to get a little melty, but still had their insulation intact. What took the fuse so long to blow is another question but I ended replacing all of the fuses in the kick panel in case I had bad generic ones or something. Symptoms included non-working taillights, and non-working dash lights. Then came the smoke, lots of it, followed finally by the fuses' small but audible pop. Two fuses eventually popped- the cigarette lighter and the tail lights :headscratch:

I have (I hope) pulled out all of the wire that burned its insulation and soldered new wire in, but as far as I can tell the dash lights are still no longer working while the tailights are now working fine (the only lights I have to go by is the single backlight for the climate controls, and the door buttons); but I haven't yet put the dash back together so it could be a connector is unplugged that would normally complete the circuit to that area. I'm trying to muck through FSM pdf's to see what the exact wires are that supply power to the dash lights (radio, gauges, power window button lights, etc) but one thing that might be helpful is which fused circuit are they shared with? Cig lighter? Tail lights? Do they require a specific dash plug to be plugged in before they work? I did temporarily plug in the gauge cluster to see if their lights worked, but no joy. I'm kind of shooting in the dark right now.

Thanks for reading, I may try to take a few more pictures tonight since I know threads with this much reading and no pics suck arse :love:

[mastacox]

Yeah, I am in the middle of rewiring the CB and a couple of switches so that they have their own fused circuits from the battery, rather than pulling power from the cig lighter. What a PITA.

[YotaFun]

Make sure you upgrade your grounds!
In my case everytime I turned on my fogs my gas gauge would drop a quarter of a tank. D'OH!

[surf4runner]

What took the fuse so long to blow is another question but I ended replacing all of the fuses in the kick panel in case I had bad generic ones or something.
if the short didnt exceed the capacity(esp if wrong) of the fuse, then it wouldnt blow, but the heat would melt the insulation, then causing a short :yikes:

be careful using the butane iron in a small area...ive melted the insulation off other wires from the exhaust heat :confused:

[corax]

be careful of cheapy fuses. one of the field engineers for the company I work for ran across a vehicle that started on fire because of a fuse that never blew. during his investigation, he found the dealer had replaced a fuse before the fire. he took the fuse and with 12 gauge wire shorted it across the battery terminals - the insulation melted and caught fire before he threw it on the ground, the fuse never blew (DON'T buy Harbor Freight bulk fuses, the tech at this dealer did).

[4runnerchevy]

Don't by anything from Harbor freight, especially fuses. Just the coating on that China crap is enough to kill you or your little kids. They have no standards and would probably like to see us die.

[mastacox]

Well, I have the dash all back together and everything is working EXCEPT the none of dash lights work... Turn on the headlights; both they and the taillights work fine, but the dash doesn't light up with them. I'm trying to sift through the FSM to find which wire might be the culprit... but if anyone knows off the top of their head where the problem might be it would be much appreciated.

I'm thinking the problem is near the fuse block in the driver-side kick panel, between there and up near the gauges. I had the entire wiring loom apart from the passenger side of the dash to just before the gauges, and any wires that were damaged in that area were replaced so there really isn't much wire left I haven't looked at... :shake: What I really need to find is what single wire (or circuit) that turns on power for the lights in the gauges, the A/C controls, and the radio. If I can find that wire, I'm pretty sure I'll find the problem.

[04 Rocko Taco]

did you test those lamp sockets with a meter, see if they were getting power at all?

[corax]

This may sound stupid, but is the dimmer switch hooked up and turned on?

[mastacox]

did you test those lamp sockets with a meter, see if they were getting power at all?


I tested the light in the ash tray, no voltage... Haven't really tested anything else.



This may sound stupid, but is the dimmer switch hooked up and turned on?


Not stupid, but it is plugged in and turned on. Good idea though...

[4runnerchevy]

This may sound stupid, but is the dimmer switch hooked up and turned on?


Not stupid at all, maybe the rheostat (sp) is bad.

[mastacox]

Not stupid at all, maybe the rheostat (sp) is bad.


Could be possible, but it was working before the short?

[corax]

is it possible that the short drew too much current through the rheostat before the fuse blew? I don't know if it's part of the circuit you were working on, but if so it could have been damaged. The easy way to check would be to "bypass" the rheostat with a short piece of wire with 2 spade terminals on it. check the FSM wiring diagram & hopefully it'll show current flow through the switch. Does the rheostat give a path to ground or +12V to the lights?

[ETRNL]

you havent by chance installed a new radio have you? i had my wiring harness smoked due to a cd dimmer wire (+12v)installed to the Toyota dimmer wire which is a switched ground. $5500 later i finaly got my vehicle back up and running. might not be the case but i had my stereo installed for 2 years before it started frying things..

[4runnerchevy]

Don't quote me on this and please correct me if I am wrong. I believe the rheostat gives a path to ground via adjustable resistance. It has been a long time (20 + years) since electronics class. :(

[mastacox]

Don't quote me on this and please correct me if I am wrong. I believe the rheostat gives a path to ground via adjustable resistance. It has been a long time (20 + years) since electronics class. :(


It's very possible, most things in Toyotas are ground switched rather than positive switched; I think I'll just pull the rheostat out and Ohm-meter it, that should tell me if its good or not. haven't worked on the problem for a while, have been busy installing toys on the '98 4Runner and stuff. I just hope I can fix this problem without pulling the dash apart again.

[avstanley]

Did you ever get the dash board lights to work again? I have had the same problem with my 1995 4Runner.

[CJM]

I had this same problem, found the rheostat to be bad and replaced and it worked.

Here is a way to test it: Testlight to a ground and touch the problem to the plug of the rheostat, if its the rheostat thats bad thelights will turn on.

[mastacox]

I never did get the dash lights working, I ended up selling the 4Runner "as-is" so it's the current owner's problem now (and he hasn't fixed it either) :P

That things has had a lot of electrical gremlins since that cig lighter short; lately I hear the turn signals started blowing fuses sporadically ... glad it's not mine any more :tapedshut: I'm convinced the problem is near the fuse box on the dimmer switch line (or the dimmer switch itself) but the only way to fix it for sure is to cut the harness open and find the culprit wire. The melted wire was right in the middle of the loom when I cut it apart the first time- no telling what it might have melted to.

[avstanley]

After spending 4hrs taking a part the dash and checking the rheostat and blowing multiple fuse in the process, I discovered that the aftermarket radio that had been installed was hooked up wrong. They had the G and W/G wires for the dimmer function from the factory radio tied together. Not sure why but it had not blow the fuse, just disabled all the lighting controlled buy the dimmer rheostat.