Ahhh. Never looked at that. I dont know how a short would be in the switch line since that acts as a ground itself. What it seems like to me, terminals 4 and 2 is what pulls the switch in the relay so that voltage can flow through 3 and 1. 4 is positive, it has voltage going to it, 2 should be the ground and when you turn your light switch it connects to ground completing that circuit which charges what looks to be some kind of "magnet" that pulls the switch over between 3 and 1 allowing that to flow. If you look at the very first diagram that you listed it shows that is what should be happening.

That is if my dyslexic idiot brain is correct .

Cherry said:

I dont know how a short would be in the switch line since that acts as a ground itself. What it seems like to me, terminals 4 and 2 is what pulls the switch in the relay so that voltage can flow through 3 and 1. 4 is positive, it has voltage going to it, 2 should be the ground and when you turn your light switch it connects to ground completing that circuit which charges what looks to be some kind of "magnet" that pulls the switch over between 3 and 1 allowing that to flow. If you look at the very first diagram that you listed it shows that is what should be happening..

Click to expand...

so it looks like i have some mother-massive short on the power side of the circuit.

out of desperation, looking and not finding the problem, i devised a contraption which hooks up a fuse to one side of the fuse terminal and completes the circuit by grounding it to the chassis... see pic:


anyway, ... with the battery (-) terminal disconnected and no key in the ignition i inserted one side of the extended fuse into the power side of the fuse receptacle and as soon as i touched the battery (-) post with the ground cable the fuse nearly exploded.

so.. at least now i know which side of the circuit the short is on... the solid red power wire leads to this terminal while the RW wire is the ground side of the fuse.
If i am reading the diagram correctly, and i hope somebody can verify and confirm this, the short is not under the dash but some place between the fuse and the tail lights and relay. I am thinking that the short to the ground is in a place closer to the tail lights rather than under the dash, the wire is grounded, the amperage skips the components/tail lights, takes a shortcut via chassis to the battery and from the battery it circles around and blows the fuse.
would that be a reasonable assumption and i should start looking for this at the back of the car rather than under the dash... ? that's the question...

edit: i guess i could confirm this theory by pulling all fusible links and high Amp fuses out and then inserting them back in one by one and see which one blows the 10Amp tail light fuse...

The parking lights tail lights and dash lights should all be on the same circuit so you just have to narrow those ones down. I would really start in the engine pay looking at the front parking light wires. These are more exposed to the elements and to critters like mice that for some weird reason love to chew the insulation off of wires. Once you get into the cab however trying to find the short all of the wires are on the drivers side just for ease.

You just gotta find what is shorting to ground. It could even be the rear side marker lights that are in the bumper, those are kind of exposed to the elements and something could of crawled up the bumper and started chewing. Check was is easy to get to first before you start taking interior panels off. I would say its much more likely for the front parking lights or the rear side marker lights to be the cause.

What makes it bad is most of the wires are in some kind of plastic conduit or taped up. Usually, at least from my experience, the wires inside the conduit or taped up are usually still good and its the wires that arent in the tape or conduit that get hard and brittle.

Cherry said:

The parking lights tail lights and dash lights should all be on the same circuit so you just have to narrow those ones down. I would really start in the engine pay looking at the front parking light wires.

Click to expand...

so, since my instrument cluster is completely out of the dashboard, i went over those parking lights, tail lights, marker lights in the bumper, etc. again, pulled all light bulbs out, examined insulation and wires leading to the connectors and ... nothing. It all looks healthy upon visual examination. I did the same test as in previous post and blew 30Amp fuse... instead of just 10Amp fuse ... so i have no idea where this surge is coming from...

Key or no key in the ignition, the 10Amp fuse power terminal (closer to the front of the car and fed with current via red wire is always hot. I pulled the 40Amp fuse marked "LAMP" on my fuse box cover and which is on the same panel just diagonally to the right upper corner from the 10Amp fuse that is popping and that cut the power to the 10Amp fuse. I dont know what to think of that... other than the 40Amp fuse protects a larger circuit including the 10Amp fuse which pops on me.

Since I blew 30Amp fuse (in place of the 10Amp fuse) i would imagine the amperage surge is b/w 30 and 40 Amps. My multimeter has a 20Amp fuse so i am not thinking let alone daring to check amperage between the fuse power terminal and ground (see pic in previous post). I would imagine there is less than 10Amps on the terminal under normal circumstances... but I cannot verify this.

Also, since i am working outside, i cannot even hookup a test headlamp light between the fuse terminals to do a "wiggle test" to see if the light dims when i am closer to where the shorted circuit is...

At this point any ideas would be appreciated as i just ran out of options...

Yes the fuse is always hot. It comes off of the battery and goes to the fuse box and then that power is distributed to where it needs to go and is stopped by the relays if it goes to it.

I probably would of checked it a different way and I would of made jumpers of where the relay is to the relay and would of left off pin one and then measured to see if turning the switch would blow the fuse that way. So basically you could make some jumper wires which would be pretty simple. Ill have to find the connectors but its night time right now so that will have to wait. The jumpers would be easy to make and it would also tell you if everything else is working properly.

But with the jumpers when you turn the power on, if the fuse doesnt blow you absolutely know its after the relay, if it does then something else is going on.

Someone else would probably have to jump in though since my knowledge is limited. Like I said before I just created a completely new light harness basically but now that I have my car running well enough until I figure out the real problem that is going on which requires more research, I can actually look at my light circuit which should increase my knowledge on it. If work doesnt go on long enough I can do some tests on my stock system which should still be functional other than none of my lights are connected to it, I should be able to help a little more and take some pictures. As long as the red wasps stay away .

Cherry said:

Yes the fuse is always hot. It comes off of the battery and goes to the fuse box and then that power is distributed to where it needs to go and is stopped by the relays if it goes to it.
.

Click to expand...

there appears to be some other component between the battery and the fuse to bring the amperage down either by regulating it or increasing resistance and keeping it under 10Amps. the other side of the fuse, which is the RW wire, goes to the tail light relay and from the relay to column switch, front combo light etc. so i am not quite sure if that side needs to be investigated since the current does not get there due to the blown fuse... which protects the components (relay, lights, etc.) behind it.

Needless to say, the 40Amp fuse marked LAMP cuts the power to the 10Amp fuse and it's on the same panel and the wires underneath the panel are solid so i am thinking the 10Amp fuse gets hit with amperage b/w 10 and 40Amp since it's getting through and blowing the 10Amp fuse. i am thinking that if the 10Amp fuse is there, the current reaches the relay and the relay keeps the circuit open and once the ignition key is turned to ON position the relay closes the circuit and energizes the tail lights etc. needless to say, i am speculating here, ... not stating this as facts.

Pins 4 and 3 should have constant power that flows from the 10amp fuse, 2 should be the switch and 1 goes to the lights. When you turn the switch to on power flows from pin 4 to 2 which then pulls the connection together inside the relay allowing power to flow from pin 3 to 1. That is what the diagram is saying. Why the fuse would be blowing however is the question.

It looks like that it isnt the power supply that dictates what the amps are but its the actual item that is using the power which draws certain amps which makes sense.

With my light wiring harness that I made this is how it is done, it goes from the battery to 3 toggle switches under my radio, then those 3 switches go to a fuse box and also have in line fuses if it doesnt the wire doesnt go back to the fire wall, each with 10a fuses in them I think if I remember correctly. The lights dont draw many amps since you take the wattage and divide it by the voltage provided. So the dims for the 1157 bulb which would be the tail light would be 8.3 wats and the voltage provided would be 12-14 volts so that is around .5a. Now that is probably per bulb and there are 4 tail lights so that would be 2a at .5a per bulb and then you have to calculate the 2 front parking lights and the 2 side marker lights which I think are the same and I think those draw .2a so at best those would be 1a so thats 3a draw so the 10a fuse should be more than enough.

So there has got to be a short to ground somewhere after the fuse which would include from the fuse to the relay and from the relay to the lights. It seems like you just have to dig and find it. It could even be the bulbs themselves creating the short so new bulbs all around would be a good starting point.

Cherry said:

Pins 4 and 3 should have constant power that flows from the 10amp fuse, 2 should be the switch and 1 goes to the lights. When you turn the switch to on power flows from pin 4 to 2 which then pulls the connection together inside the relay allowing power to flow from pin 3 to 1. That is what the diagram is saying. Why the fuse would be blowing however is the question.

Click to expand...

i have continuity from the fuse to pin #3 and 4 so at least it's not a broken/loose wire...good chance the short is not on this path.

Cherry said:

So there has got to be a short to ground somewhere after the fuse which would include from the fuse to the relay and from the relay to the lights. It seems like you just have to dig and find it. It could even be the bulbs themselves creating the short so new bulbs all around would be a good starting point.

Click to expand...

i pulled all light bulbs out, checked them for continuity and also if they work.. they do. in any case, with the relay out and all the light bulbs out (tail lights, marker, parking) i ran the earlier test with the fuse but with 30Amp and it holds whereas the 15Amp popped the last time so i am looking at surge 15>30Amp.


now i am thinking if license plate lights are somehow hooked to the same circuit... there's usually some rust..

They are, at least should be. I was able to tie into 1 wire in the trunk to get the tail lights side markers and license plate lights to work. It would be good to check those wires as well. They shouldnt be too bad to inspect if I remember correctly.

Basically it doesnt matter how many amps you are pulling since you are pulling over 10a which the entire circuit should only be pulling like 4-6a. Each tail light pulls around .59a the parking lights and I think rear side markers are around .28a? or close to it and the license plates are probably close to that so that should be 4a roughly that the circuit should be pulling. If it is pulling more amps than 10a to blow the fuse then something is pulling more amps which is usually a short to ground somewhere and it is most likely going to be between a light somewhere and the relay, the hard part is finding it.

You have parking lights, cluster and dash lights, tail lights, rear side marker lights and license plate lights to check, and then follow the wire or even probing sections of wire checking for continuity. Since Ill be doing wiring tomorrow for a Vibrant windshield washer bottle ill probably do some testing on my light circuit since one night all my lights just shut off. I think that is going to be harder to figure out than a short to ground. It could even be my entire switch and I doubt I can get a new one.

Oh, and since I was outside I figured out with some jumpers that I got the pins on the relay wrong, ill have to edit the picture. Basically 4&3 should be 3&4 and 2&1 should be 1&2 in the picture. Ill have to update the picture.

I did figure out what was wrong with my lights though which there was a bolt missing from where the power wire hooks into the relay box so the power wasnt flowing all the way through it. I didnt know there was one that was supposed to be one there or why it was even missing but I just took a bolt that was from my Vibrant windshield washer fluid bottle and pit it in there and now I have everything back basically. Now I will have to hook everything back up to the factory harness which wont be bad at all.

The numbers on the relay however and where they go are still correct, I just labeled them wrong, so 1 still goes to the lights, 2 still goes to the switch, and 3 and 4 should still have constant power. I had to make some jumpers to figure it out though.

Cherry said:

I did figure out what was wrong with my lights

Click to expand...

good... i'm still struggling here. i am now into hunting for connectors C48, C45, C54, C06, C68, D10, C69 so i can un/plug them and see if i can narrow down and isolate my search for the broken circuit...
i do suspect this is related to the after market anti-theft system where tons of wires were spliced and hacked up.. .what a mess
the installers likely hacked and rewired some circuit so that tail lights start flashing when the system is triggered...

I have to find the reason why there is no power going to my windshield washer bottle and I cant even find a schematic on it so I have to trace the wire which will be fun.

Cherry said:

I have to find the reason why there is no power going to my windshield washer bottle and I cant even find a schematic on it so I have to trace the wire which will be fun.

Click to expand...

...not sure if you looked at this:
The 1990 Engine COMPARTMENT Wiring Harness
in any case, i find a lot of electrical articles in this section:
https://www.dsmtuners.com/forum/tech-article-archives.42/
or here:
https://www.dsmtuners.com/forum/articles-electrical-wiring.40/
or here:

Looks like I wired into the wrong connector . Wired into the fog light and not the washer motor. I had taken the entire bottle out before and assumed the connector that was right there but apparently I had put the fog light connector in the area of the washer motor.

Oh well I get that fixed tomorrow since I will have the soldering iron out tomorrow getting the lights wired back in to the stock harness.

Oh well, its nothing major and nothing that cant be fixed, sometimes you just mess up.

Cherry said:

I will have the soldering iron out tomorrow getting the lights wired back in to the stock harness.

Click to expand...

here's another good document -- service manual for electrical issues - if it's of any use:

Alright, I tried to edit my previous post that showed what went to where but I cant edit it so it looks I will have to make a correction here.



I checked it with jumpers that I made so I could check which was what since diagrams are either the relay itself or where the relay plugs into. Anyways this should be the updated and correct layout for the tail light relay. I should take a picture of the jumper I made if you want to make yourself a pair set. Good to test things without trying to get to the backside of the relay box. Though it was me trying to get to the back of the relay box that made me find my issue.

Just didnt want bad information out there. I wish I could of edited my other post but I couldnt.

Cherry said:

. I should take a picture of the jumper I made if you want to make yourself a pair set. Good to test things without trying to get to the backside of the relay box.

Click to expand...

that's great information ... it will be useful.
i found the problem... it's the cigarette lighter that's somehow shorting tail lights. i'll do more checking and write it up...

The ring around the cigarette lighter is with the dash lights. Im about to toss my car in the junk yard to be completely honest. Cannot get my idle set, something isnt working right or there is a major leak somewhere and I dont have the time patience or money to deal with it.

Cherry said:

Im about to toss my car in the junk yard to be completely honest. Cannot get my idle set,

Click to expand...

Can you get 5V signature voltage on the coolant temperature sensor wire? and are the contacts clean - both the sensor and the connector? surprisingly, this wire/lead from the CTS goes straight to the ECU and can affect how the engine idles and runs. also, check if the CTS functions the way it is supposed to... there's resistance specs for temperature ranges the CTS supposed to modulate the voltage going back to the ECU.
this was my issue with the CTS:
Take a listen (video)... intermittent or persistent misfire?

Its a brand new CTS and new connections on it and new most everything. The only thing left to do would be to rebuild the throttle body. The only reason im not using my s90 is because that thing leaks as well out of the box and the JM Fab intake manifold doesnt seat properly with its build in gasket. I could make my own gasket and try to figure out a way to get the s90 to stop leaking on the throttle cable side and see if that fixes things.

But when setting the idle which I got the timing to 5 degrees BTDC where it is supposed to I cant even get the idle down under 1000rpm, though when the BISS screw is screwed all the way in it stalls. It even idle surges with the timing and diagnostic plugs grounded out, and it even surges when the FIAV housing was completely blocked off. Its just a headache at this point. If I do make some gaskets for the s90 and JM Fab manifold then I have to get another thinner battery and I wish there was a way to raise the JM Fab manifold up so that the bottom of the FIAV isnt tangled up with the shifter cables. I know of a machine shop that I could probably get some stuff made at but im tired of throwing money at this issue with it just getting worse and worse.

Cherry said:

I checked it with jumpers that I made so I could check which was what since diagrams are either the relay itself or where the relay plugs into. Anyways this should be the updated and correct layout for the tail light relay.

Click to expand...

your diagram is handy. i am still trying to figure out why the cigarette lighter socket is shorting the tail lights. i found the connector which disconnects the body wiring harness. the body harness connector is right behind the driver side fuse panel. there's two of them and it's the first one from the bottom. it looks like this:

that disconnects tail lights and rear side marker lights. the instrument cluster, dashboard is still lit and the front side orange lights are still on but the connector to the cigarette ligher has to be disconnected otherwise the 10Amp fuse gets smoked as soon as the lights are turned ON. the connector to the cigarette is located on the driver side console/pillar which houses the radio and ECU. it looks like this:

So, to track the short I reconnected the cigarette lighter connector ^^^ and pulled the 10Amp fuse in the engine bay as well as the tail light relay.

then i made a test light with a 10Amp fuse attached to it. It looks like this:

the probe is attached to a 10Amp fuse and the white ^^ lead goes to one side of the light while the other side of the lamp is connected to battery (+).

I know the short blows the fuse so i started testing the relay terminals. With no key in ignition and the light switch on the steering column in OFF position I expected no power on any of the 4 terminals. With the red lead connected to the battery (+) i inserted the probe connected to the white lead into relay terminals #2,3 and #4 and none of the three terminals was pulled to the ground so the light did not go ON. However, once I touched relay terminal #1, the light came ON. That tells me terminal #1 is grounded (shorted)... some place down the stream.


if I am understanding your diagram correctly, terminal #1 goes "to lights". In other words, logic would dictate that the short is some place between the disconnected harness and relay terminal #1. However, what does that have to do with the cigarette lighter is mystery so far. I tried the wiggle test and the light did not flicker to show me i am close to the point where it is grounded. But as soon as i disconnect the cigarette lighter the "short" disappears. I guess i could keep the damn thing disconnected but since i already spent all this time on it, I might as well find the problem.

As I mentioned in earlier posts, I was dealing with a non-functioning anti-theft system. I took it all out thinking i will find the short but i am still looking for it. As you can see below, the anti-theft unit was somehow wired to the middle console, around the cigarette lighter socket, and some kinda switch and light was added:

shaking these wires ^^^ does not help as they are disconnected so i guess the short has to be some place where the installers tapped into source of power which affects the cigarette lighter. Btw, the cigarette lighter works... no issues whatsoever.
So, any ideas would be helpful... I need to find the wiring diagram for the cigarette lighter

Cherry said:

The only thing left to do would be to rebuild the throttle body.

Click to expand...

any luck with fixing the idle surge? this appears to be a common problem. I did a cursory search for "idle search" and tons of stuff comes up. The majority of cases have to do with ECU, TPS and ISC... some also ISP. One poster also wrote:
"I fought idle surging on my 1g for years and years...one day someone mentioned the idle stop screw being out of adjustment. So I did the feeler gap check and sure enough the damn throttle plate was open too far. Adjusted it to proper spec and never had idle surging issues again"
In any case..

Is that alarm still hooked up? If so, just so you know, if that alarms light flash wire is still hooked up (should be a white wire going to the parking light circuit), on the alarm box there should be a little door with a fuse in it. That selects the parking light output polarity (also depends on the type alarm). So if they hooked to a positive wire and have it on negative, that could be the issue. Vise versa if they hooked to a negative and have it on positive.

Clipsoe said:

Is that alarm still hooked up? If so, just so you know, if that alarms light flash wire is still hooked up (should be a white wire going to the parking light circuit), on the alarm box there should be a little door with a fuse in it. That selects the parking light output polarity (also depends on the type alarm). So if they hooked to a positive wire and have it on negative, that could be the issue. Vise versa if they hooked to a negative and have it on positive.

Click to expand...

Thank you .. this is definitely a solid lead. I have been suspicious of something like you suggested and that was the reason i cut the non-functioning alarm system out of the car; however, I have marked every wire diligently so i know where everything goes:


Since the alarm is cut-out, the only thing left would be some place where the wires were intentionally switched to draw power and keep the alarm system alert. Electrical systems are not my forte but as i observe it, the connecting/disconnecting the cigarette lighter completes the circuit and triggers the short which, as you suggested, is caused by reversed polarity some place on the parking light circuit. Furthermore, when you say "parking lights" are we talking about the back side red markers (in the rear bumper) or the front orange side markers beside headlights as parking lights?

The only wire they should be grabbing at the console for a remote start system should be the parking brake (which is a ground). As far as parking lights, I am referring to the lights beside the headlights, but by powering one wire with the alarm should activate all the lighting as if you turned your headlight switch to the first position.