Topic: wiring problem along door sill

[Justin]

ok so now with the new harness in place my dome light works so thats great. but I also traced the big black wire/ground that was in the door sill also and it goes back to the fuse box and clips into a little blue clip into one of the accesory spots and down to a metal fuse or something at the bottom of the fuse box..heres a picture of it. it behind that metal plate..any idea what that is ?

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[Justin]

I have yet another question. On the back of the headlight switch there are three prongs in a line but on the actual harness itself there are only two. is this that way its supposed to be?

[Justin]

Im half tempted to just unbolt the headlight wiring harness from the firewall,I already have the tail light unplugged..then it can only be under the dash right???

[Justin]

so thats what I did. I unplugged the headlight harness from firewall and still blow fuses.

[Justin]

now I replaced the switch and still blow the ame fuse. is there anything this switch powers under the dash?

[Justin]

any suggestions at all? If everything is unplugged what else could it be?

[78ta]

I see you've been at it all day today. Sorry, I just got home a little while ago. Sounds like you've made some progress on your own though.

If you have the rear harness and the front harness disconnected, then I believe the only things left are the dome and courtesy lights and the wiring from the fuse box to the headlight switch. That big black wire concerns me. Not sure it's the problem but it obviously isn't stock. You said it goes to something behind a metal plate. The pic is too small to really make out what's what.  I would unplug that black wire and see what happens then. You can email the pics to me at w70442@hotmail.com if you'd like.

Can't help with how many pins are supposed to be on the plug for the head light switch. Just don't know.

I haven't looked at the schematic but I'm almost positive that the things that should come on when you pull the head light switch straight out one click or one position is the two orange parking lights in the bumper up front, the two orange marker lights in the front fenders, the two red marker lights in the quarter panels, the rear tail lamps which have three bulbs in each lens(L and R) and the two license plate lamps. One on each side of the license plate.
You said that your dome light is working now since you replaced the harness but, and you probably already know this, the dome light and the two courtesy lights under the dash should turn on when you turn the head light knob all the way to the left(counter clockwise) regardless of whether you have the headlight switch pulled out one click or two clicks or not at all. Just turn the knob to the left all the way and the dome and courtesy lights should come on. You've replaced the headlight switch and it does the same thing so it's 99% ruled out. It's unlikely but possible that the switches are bad in the same way. So, assuming that the switch is ok, if the knob is NOT turned to the left all the way when you pull it out, the dome and courtesy lights are NOT in the circuit so they can probably be eliminated. IF, however, the switch knob was turned all the way to the left, then there could be a problem in that circuit. You said that the dome lights work though so I assume that means works as it should with out blowing the fuse.
That leaves us back at that black wire and the fuse box. As I said, the pic is small but I think I also see some other orange wires that appear to be just stuck into fuses. I would remove or umplug any wire that does NOT look like it was installed at the factory.
You're getting closer.......

[Justin]

ok..My nieghbor whos a mechanic at a ford dealer tested the black wire and said its a power wire but ill unplug that just incse...it almost seems if thats a power wire and it was connected to the bad wiring harness someone was trying to cut into the line to get power without findout what the problem was. I am also going to check the under dash lights and see if that wiring is messed up. The harness for the dome light plugs in in the trunk and must be off seperate fuse because I ge power there and the door strikers work. can anyone tell me what kind of buld should be in the rear panel marker lights? it has just one contact point in the connector and is to the side...im thinking a 1156.

[78ta]

I think the metal thing under the fuse box that the black wire goes to is the noise filter for the radio. It's a capacitor and it could be shorted which would cause the fuse to blow for that circuit. Unplug that wire and see what happens.

[Justin]

clock stops working. No radio either.

[78ta]

Ok. I assume when you removed that black wire, you put a fuse in the spot that was blowing to see if it is still blowing. If it did blow with the black wire out, and the clock and radio were working ok before, they and that black wire are obviously on a different fuse. That's ok. You can eliminate that black wire as a cause. As I said, troubleshooting is largely a process of elimination.

Did you put a new fuse in when you had the headlight switch unplugged? That would eliminate the switch and everything down stream from the switch(after the switch).

When you pull that knob one click, a lotta sh** happens. I'm looking at the schematic and see that the turn signal indicator bulbs (and wiring) in the instrument cluster, all of the lighting inside the instrument panel and the gas/voltmeter bulb, the dimmer switch, the light for the a/c controls, the turn signal flasher and the four way flasher could all potentially be the problem. I doubt that it is the dimmer switch because it should not come into play until the headlights are turned on(switch pulled all the way out). If it still blows with the switch unplugged, the problem is likely between the fuse box and the headlight switch plug. If you unplug the headlight switch and the fuse does NOT blow, then unplug the instrument panel and see if it blows. If it still blows, unplug the 4 way flasher and the turn signal flasher. Doesn't really matter which of these you do first. Just keep track of each step. Writing down what you've done helps a lot when you have to go back and verify things.

We've all heard of people putting gum wrappers in place of fuses. If you don't know the history of the car or you know this has been done, you might want to go through the fuse block and remove any foriegn items that you find.

That oughta keep you busy for a while......... Good luck,

[Justin]

hey Thanks for all that info. Like I said before I didnt know what all ran from that fuses. Last night I went out to the car wit my nieghbor and checked the wiring. since taking that un known black wire off the old tail light door sill harness I no longer have brake lights. I still have the turn signals on the tail light part but not the side ones in the back. The hedlights work when you pull the swtich two clicks but blows the fuse the first click as it always had. It never blows without pulling the switch one click. I do not have an instrument panel light at all. I am going o unplug those and see what happens. I also dont have my a/c control hooked up because it looks like someone cut the wire straight from the harness. Im going to right down all the things that are hooked to that circut you told me about and eliminate best I can. Thanks again. If nothing else it looks like I might have to just by pass the fuse box right?

[brian c]

Do NOT bypass the fuses. They are there to protect your car from an electrical fire.

Here's what your headlight switch will turn on/off...

1 click....all outside marker lights and all interior instrument lights. This means front, rear, and side markers along with your gauge clusters, shift indicator light, heater controls and (if rotated fully) your dome light and (if equipped) the deluxe interior lights at your feet.

2 clicks... everything the first click did PLUS your headlights.

So if the headlight switch has been replaced and your turn signals are working I'd seriously look at the wiring under your hood going to the headlights. Check for any sections that are missing insulation or are burned through.

Then tackle your brake lights    One problem at a time afterall. It'll make your trouble shooting process much easier.

[78ta]

You're welcome.

I agree with Brian. You don't want to bypass the fuse box. You've gone through too much with this car already to have it go up in smoke. Keep at it, we'll find it.

Brian, he said in an earlier post that he has the front body harness and rear body harness disconnected so they are eliminated. It's got to be inside the car. You do still have those unplugged, right Justin?

Justin, you mentioned that someone competely cut the a/c wires. I wonder if the wires in that plug got mashed(shorted) together when they cut them. I'm wondering about the printed circuit board. Those are known to go bad though they usually just create an open and not a short but I suppose it could happen.

You're on the right track. The way to troubleshoot this with fuses like you are is to disconnect EVERYTHING that is in that circuit, put a new fuse in and then plug things back in ONE at a time until the fuse blows. That will tell you which item is causing the problem. Keep in mind that you may have two things that are shorted so if you find one that blows the fuse, make a note of t, unplug it, put a new fuse in and go on plugging the other things in one at a time just to verify that there is not another short in the circuit.

[Justin]

ok so heres what I have. I unplugged everything that has anything to do with that fuse. I looked to see if maybe the wiring harness for the a/c or radio are mashed and dont see anything. fuse still blows. I just talked to a guy last night and he said it might even be the lighter. Im going to check that out now.