IngSoc

So I checked all my fuses... Good. I swaped the wired between my headlights/marker lights and the switch is good. It would seem im not getting power to the switch connecting harness. Im not sure how to check my taillight relay to see if it is still good but from there IDK where to go. Trace the wires back from the tail lights? Been an ongoing prob for a few months now so any help is truly appriated. Thanks.

mschein1

Guessing you have a crossed wire somewhere possibly.

mountaingoat

Check the fuse box itself, the circuits in there can crack sometimes.

IngSoc

When I did my cab swap some how the wires got smushed inbetween the frame and the bed and the fuse began to blow ALOT. I fixed that problem and about a month later this started to happen. How would I go about checking the fuse box?

IngSoc

So I didnt get the new relay seeing that they are out of stock @ this moment... I dloaded the FSM and it was telling me to test continuity between post 1 & 3 I belive ( what ever one it was) Instead of getting a beep on my meter it started throwing out numbers. With the switch on I wasnt getting any juice to the fuse box where the relay sits. Any help please?

Hadmatt54

Is it your brake lights or your taillights, because the brake lights are on a different circuit than the dash lights and marker lights. If you have lost all of these circuits then your problem is multiple and I'd be going back to where you "smushed" the wires. If you are not blowing fuses then you don't have any wires shorted, but you probably have wires open (broken). You don't have much choice in tracing the wires, but there is a connector that is located under the passenger seat, which will allow you to disconnect the back harness allowing you to narrow down your problem.
On testing the relay, it was probably a continuity check across terminals 1 & 2 you wouldn't read anything across 1 & 3 until the relay picks-up and the contacts close.
If you are checking continuity on a piece of wire with very little resistance you will get a beep indicating a good path for current flow, however when you checked the taillight relay you were measuring the relay coil, which has a significant resistance value. In this scenario you will not get a beep from the multimeter, it will actually measure the resistance value and give you a number in milliohms, ohms, kiloohms, ect. It will tell you the resistance of the relay coil

IngSoc

Well im not sure if the breaks are a recent devlopment but yeah the Markers and dash dont come on. So if there is resistance in the relay its still good? Why wouldnt I be getting juice from the plug that it plugs into?
Oh and thanks a million for the advice this has been racking my brain for weeks now and I didnt think of the connector.

Hadmatt54

Yes! Resistance indicates that the relay coil is intact and it's not shorted or open. Now whether it is the proper resistance, well that is another matter! The FSM does not give a resistance value for the coil. It just states that there should be continuity between 1&2 and no continuity between 1&3.

You should read battery voltage between Terminal 1 of the relay plug and ground, as it comes directly off of the 40 amp. Fusible Link AM1 which is in the fuse block under the hood.

I'm not sure what you swapped...please explain!
Where your problem is not only tail lights, but dash lights and front marker lights, that could be a faulty headlight switch. To check it if you unplug the harness from the light switch pigtail on the underside of the steering column there are 13 wires. On the pigtail #1 will be the very top right terminal. #10 is the large wire in the center bottom of the connector, there is no wire above it. #11 is left of #10 on the bottom. With the headlight switch on in either parking light or headlight position there should be continuity between 10 & 11. Also check #11 on the harness side there should be battery voltage from #11 to ground all the time.

How did you check all of your fuses? Did you put your multimeter across the fuse and check for continuity? I've seen fuses that were open according to a multimeter, but looked perfectly normal.

There might be multiple things going on here, a faulty reostat switch would put your dash lights out. To check it unplug the connector, set your multimeter to ohms and put your leads on the two terminals of the switch. Fully counterclockwise there is infinity resistance, which means the resistance value is so large your meter can't measure it, your display may show error. Fully clockwise the resistance will be zero ohms, halfway in the middle you should read approx. 7 ohms.

What else have you noticed that isn't working on your truck?

IngSoc

So I did what I think your pretty much telling me to do and swapping the wires coming down from the switch to make it so the lights turn on on the marker switch and the markes and lights come on with 2 turns. im going to hook some juice up to the connector under the seat and see if that works. Im still pretty stumped why im not getting juice in the fuse box where the realy plugs in.

For the fuses I took them out and did a continuity test on each one. Looked super carefully at each one (replaced the older looking hinky ones) Any one mind telling me what the resistance on their realy is?

Hadmatt54

The fuse element opens according to a certain time/current characteristic (TCC)curve. This is an exponential curve (remember your high school math) in which the fuse element is designed to allow a certain amount of current flow over a certain period of time. Time is the verticle axis and current is the horizontal axis. An instantaneous (high current) fault would be a plot on the bottom of the curve, because little time would evolve, whereas a fault of low current for long periods of time would be a plot on the upper part of the curve. Fuses want to have very low resistances as you you do not want them to resist current flow because this causes heat and heat causes the fuse element to melt opening the fuse. Generally when you check a fuse with a multimeter you are checking for continuity, not resistance.
Just to give you an idea of how little resistance fuses have. A 69,000 volt 100Amp power fuse for a Electrical Substation transformer, is about 40" in length and weighs about 25 pounds. It has a resistance of 0.01 ohms!

IngSoc

Thanks im actually going to school for electronics engineering (first semister) and just fully wraped my head around ohms/watts law V=IR => P=VI. and just started playing with resistors and the voltage curve. Im not sure if I mistyped but I did check continuity on the fuses not the resistance. The resistance I was refering too was the relay. Now are you sawing the relay is more of a fuse than a switch? What im not understanding is why im not getting any current to the location that the relay sits. NAPA is getting the realy in but its going to be to the sum of $57 and not really looking to spend that then not be able to return it if that is indeed not the prob.

Question: If the relay is un-pluged from the fuse box can I test the circut by putting my multimeter ground to the ground screw(body) and + in pin 1 ( I belive is the pin) and with the marker switch on I SHOULD get a reading?

See im figureing no power to the relay is the problem and since I know the light switch is good... I mean I would wrather test around the relay then drop $57 to figure out thats NOT the prob.

Sorry if im being an idiot. I tend to do that from time to time, but like always. MUCH MUCH MUCH MUCH appriciation for everyones help!

Hadmatt54

Good luck in the electronics engineering field!!!
I guess I mis-understood you about the fuse testing, no the relay is not like a fuse, the coil does have a certain resistance, but the FSM doesn't list what it should be.
Yes you can test the relay out of the truck. Remove it and you will notice that this relay only has three wires, normally there are 4, but 2 & 4 are connected internally. Conect 12v (+) to # 2, (-) to #1and you should hear the contact close (click) which would allow you to measure 12v to ground at #3. If it doesn't do this then your relay is faulty.

IngSoc

Could not imagine this would have ANY THING to do with it.... Goes back from both sides of the conector like this. Blue wire I belive is my fuel pump and the green is definately the issue. You think this would probably blow the relay ?

IngSoc

You rock! Mahaloz!

Hadmatt54

Typed my last post pretty fast before I went to work this morning! Originally I said 1&4 are tied internally, I edited my post..should have been 2&4.
That picture that you posted it looks like connector N1. Is your truck an auto?

IngSoc

That is the connector under the pass seat going to the rear harness. Its a manual tranny. Going to rip out the dash today and track down the wires and make sure they are all G today and might end up getting the relay if that dont work.

IngSoc

Hrmmm. So I know the rear harness is good. Put juice through it (from under the pass seat) and all the lights came on.
I am noticeing that when I do a continuity check between the green wires ( light + ) and the white wires ( - ) im getting continuity all the way up to the white plug into the fusebox. Does that mean I have a short?
One of the green wires was burnt pretty bad from the lights up past the connector and till about where the ECU is. Seems it was only burning where it was touching the body, so I replaced all that wire.
I tested the relay the way you suggested and it was clicking as stong and healthy as ever, so thats a relife I was just about to go buy one before I read your post.

Im still not understanding why im not getting power to where the relay goes. With the switch turned to markers or headlamps I should get a 12v across pin1 (-) and pin2(+) correct?
.... You wouldnt happen to the fuse layout for the driverside kick panel fuses would ya?

IngSoc

So moving right along with this headache I have got continuity from the plug into the back of the fuse box to the lights. If I bypass the fuse box and hookup currant I get the lights to go on! Soooooo I have narrowed it down that the (1b) connector isnt getting any juice. Kinda been singing that not all along but had to replace the wire from the lights to the fuse box cuss it was soooo f`ed up. Progress but no sucsess yet. Any one got any suggestions why im not getting power from the alt fuse to the 1b connector in the fuse box? Every thing elce works. Blinkers sterio etc.

Hadmatt54

Duhhhh!!!!
Guess I should read a little farther!
No Short! the bulbs are still in the circuit, you are measuring continuity through the bulb elements.

No! Pin #1 and Pin #2 are the two ends of the relay coil, there is a voltage drop across the coil because it has a resistance value, which means the two ends of the coil are not at the same potential. Your voltmeter measures the difference in potential, so across pins 1&2 you will read the voltage difference but you will not get a reading of battery voltage. However if your circuit on the coil side of the relay was OK and complete you should read 12v or battery voltage from pin #2 to body ground and battery voltage less the voltage drop of the coil at Pin #1 to body ground.

In a previous post I gave you a run down of how my 86 tailight circuit works, I don't have the wiring diagrams for your pickup, the closest I can come is for a 91 4Runner. Your relay is fed from the 100a. or 80a. alt fuse. If your wiring was okay, once you turn the switch on, there is a completed circuit from 100a. or 80a. alt fuse to #2 of the relay through the relay coil to #1 of the relay to #11 of the combination switch (headlight switch) through the contacts of the switch to #10 of the combination switch to ground. If your truck is an SR5 model you may have a Headlight Auto -cut ECU that is in the circuit between #1 of the relay and #10 of the combination switch.
That is how the coil side works.
On the contact side, the relay contact closes, there is now current flow between #2 and #3, current flows through the 15a. tailight fuse to the dash lights, through the reostat and to ground. There is also a small branch circuit to the clock and the glove box light(if you have one) that are not controlled by the reostat.
There are two other branchs after the fuse; one goes directly to the LH front parking light and to ground and the other branch goes to the intergration relay(should be on the back side of Junction Block #1 (JB no.1) which is under the left kick panel. On the back side of JB no.1 there is a 12 pin connector that runs vertical, pin 11 (Green wire). Now I can't be sure, but it looks like there are two green wires on pin 11 if so one of course feeds the integration relay, the other goes to remaining park and tail lights and the light reminder relay which is under the radio. If the tail light circuit is fed from a wire that exits the integration relay then I don't see that on the diagram.
Looking at the wiring diagram if the integration relay was your problem, if you unplug it and make sure your wiring is OK for the coil side of the tailight relay (completed circuit /closed relay contact) and verify that the 80a or 100a alt fuse is OK and your taillight fuse is OK, your dash lights and your left front parking light should work. If you can make this happen, then That would point to the integration relay as being your problem. I have a page of how to test the integration relay, if you see that it might be your problem, I can post it!
By the way your wiring is burned up your truck must have had a major short at one time.

IngSoc

Well went and got a junction box and relay out of a scrap 4runner plugge it in and..... Nothing. Seems my alt fluse is good from looking at it. Im thinking now its the wire that feeds power to the markers and dash? The whitewire. #8in connector 1b Would that make since? I feel kinda dumb asking but I wonder i this has any thing to do with doing the "big 3". Also threw a 140A alt so I upgraded the fuse under the hood to a 140a fuse. :/