Electrical help needed

I'll try to be brief.

2005 Focus ZX3 base. My mom's car so I get to try to fix it.  Switched cars with mom for a couple weeks while she is out of town visiting sis and didn't trust this ford.

Interior/dash/tail lights pop the fuse (15a) as soon as the lights are switched on. Dad decided to put a 25a fuse in and "look for a spark". He succeeded in letting the smoke out of the switch, a $60 mistake.

My first thought is a shorted/burned bulb socket somewhere. Checked every bulb and found nothing. Replaced the switch, put all the lights back where they go and installed a 15a fuse and everything seemed fine. Figured the switch might have been the problem right from the start. On my drive home that night the lights worked fine for 15 minutes then pop, no more lights. I should be clear, the headlights, brake lights and turn signals all work fine, just the tail lights and dash lights stop working, dome light works. As is the car works fine, but with no tail lights it can't be driven at night.

Traced the wires all the way and can't find any shorts anywhere. Stereo is removed (simply unplugged, not hacked) so it can't be related. And the wiring has not been messed with aside from a headlamp that was replaced after little brother was following too close to someone a couple years ago.

I'm at a loss and don't know what else to look for.

Well, something changed.  I would try really hard to find out if anything was touched, moved, worked on, looked at etc. 

if the headlight switch started smoking after putting the higher amp fuse in, that would be the first place I looked.  And if you replaced it and still have the issue, check the wiring going to it as it might have burned through and grounded itself out.   Same symptom, different problem  

If that doesn’t work, find out everything on that circuit, and start by unplugging or disconnecting everything.  

Put the fuse in.  If it pops then the problem is in the wiring before the components. If it doesn’t  pop, it is likely a problem with a component.  start adding things one at a time and maybe waiting and starting/driving until it pops again. 

Then examine that item.

Checked the wiring to the switch, looked fine. And the switch i installed was a new factory one. The fact that I messed with all the external lights (removed housings, inspected wires, sockets and bulbs) and then everything was fine makes me think it has to be one of those components. 

The really ironic thing is I have been trying to use this car as a simple cheap way to show my dad that modern cars are not the devil. He just laughs and says it has too many electronics. Then the only problem I have trouble fixing is electrical.

Look at all the lights on that circuit, carefully. Are any of them brighter or dimmer than the others?

What about the dash dimmer? Does the fuse blow faster or slower depending on the setting of the dash brightness?

Anything else on that circuit you might have missed? Auto trans shifter console lighting? A wiring diagram would be really nifty.

Ever had the windshield replaced?  The cheap place that did the windshield on our old Focus ('03 ZTW) managed to pinch a couple wires and short out the dome lights in the process.

My experience with a subaru wagon and the same problem. 

I found that opening the hatch had made the wore insulation just under the headliner crack, causing an intermittent short. It was NOT where i expected in the accordian tube from body to hatch. Chased that for 3 months. 

Front running lights are on the same circuit as the tail lights.  When brother ran into something, the insulation on one of the wires up there probably got scraped. I'd look there first.

On a whim I thought id peel back the loom a bit on the harness that connects to the headlight switch. Sure enough, burned wires. Maybe 8 wires go to that switch and the insulation was all melted together and a big fire-starting mess. I'll get some pictures up in a bit. So this harness goes up around some air ducting and into a plastic gutter-kind-of-thing with a bunch of other wires. The melty bits stopped several inches short of the main harness so I separated the wires and re-insulated them. No change. Im pretty firmly convinced this was caused by the 25a fuse experiment and that there are more melted bits of wire deep in the harness. All the fun, all the time.

 You can also take all of the bulbs out that are in that circuit. Then replace the fuse. Using the switch, turn on that circuit. If the fuse doesnt pop, then you know it is not in the wiring to the bulb sockets from that switch,  because the only load, which is the bulbs, would be removed. And if the wiring to the bulbs was the problem it would still blow the fuse. 

Is it possible that one of the filaments in one of the headlight bulbs failed in such a way that it is touching the other filament? Effectively crossing the streams?

To do a wiggle test, make a long extension, plug one end in the fuse block and put a 12V light bulb on the other, The biggest watt you can find. When you find the short the bulb will be bright. It would be safer to but a fuse in series with the bulb but not necessary.

Unplug every bulb**, and flip the switch.  If it pops, you're looking for a short in the wiring circuit.  If it doesn't pop, start plugging in lights until it does.  Replace the last light before the pop.

In the event you have a short in the system (fuse still pops with all light bulbs unplugged), you can verify it IS a short, and not the switch/relay/etc by putting a meter on the positive wire coming out of the switch (unplug the harness from the light switch).   I couldn't find a Focus diagram, but in the Mustang diagram (below) you would be looking at the brown wire, right where it comes out of the main lamp switch.  With all the bulbs removed you should have no continuity to ground. 

If the shorted wire in question is touching another hot wire you'll see voltage at that brown wire.  I think either scenario could pop a fuse.  If you find voltage, you might try pulling other fuses until the voltage reading goes away.  That might focus (nyuck nyuck) your search a little more (ie:  if the headlight fuse is pulled and the voltage goes away then you look in areas where you might find headlight wires etc.). 

** I just noticed that the anti theft module and keyless entry modules are tied into the system (that makes sense, now that I think about it).  Disconnect those when you disconnect the bulbs to do your voltage/ground/ fuse popping checks.

I had a similar problem that was the wires to the hatch. The plastic hose thing cracked and chaffed and would occasionally pop the fuse. Just a thought.

Bruce

If I get a chance tonight I'll take all the bulbs out. Supposedly I get to return this pile to my parents tonight and reclaim my car. We'll see what kind of time I have after work. 

ECM: I had that same thought, but all the bulbs look fine, none of the sockets are burned and the wiring to each lamp looks good.

Hungary Bill: I don't have a manual (repair or owners) for this car, and the Ford Motor Co, in their infinite wisdom didn't include any labels for the fuses, just numbers "refer to owners manual", so I don't know which fuse is for the headlights. The only reason I know this fuse is because the running lights don't work and the fuse keeps popping when I turn them on, real scientific. The wire colors in that diagram look right at a glance though, I'll have to compare it after work.

The weird thing is after I replaced the switch the lights all worked fine for about 15 minutes.... IDK. 

barefootskater said:

ECM: I had that same thought, but all the bulbs look fine, none of the sockets are burned and the wiring to each lamp looks good.

ECM and one or two others have hinted at the fact that a dead bulb doesn't always look like a dead bulb.

Also this may be correct info for headlight fuses for a 2005 Focus.

I think These online help rooms are fun sometimes, even if they are useless.

Welcome! What's going on with your Ford?

You

Running light circuit is fubar. Blows the fuse immediately, Found some melted wires and fixed them but still have the problem

Steve Pearl, Ford Mechanic's Assistant

Do all the fuses have the correct amperage for the circuits they're in?

You

They do.

Steve Pearl, Ford Mechanic's Assistant

What is the model/year of your Ford?

You

2005 Focus ZX3 base

Steve Pearl, Ford Mechanic's Assistant

Are you fixing your Focus yourself? What have you tried so far?

You

Checked all the bulbs and sockets, replaced the switch, and fixed some melted wires. No change.

Steve Pearl, Ford Mechanic's Assistant

Anything else you want the mechanic to know before I connect you?

You

I like my hair pulled

Steve Pearl, Ford Mechanic's Assistant

OK. Got it. I’m sending you to a secure page to join JustAnswer for only $5 (fully-refundable). While you’re filling out that form, I’ll tell the Ford Mechanic about your situation and then connect you two. Continue >>

barefootskater said:

Hungary Bill: I don't have a manual (repair or owners) for this car, and the Ford Motor Co, in their infinite wisdom didn't include any labels for the fuses, just numbers "refer to owners manual",

Ford Owner manuals are free from Ford. Download ,print out the important parts and put in the glove compartment.

Thanks for all the input everyone. My electronic diagnosis skills are very primitive. And aside form a cheap multimeter I don't really know how to use I don't think I'm fully qualified for this kind of work, but I'll keep plugging away.

you said one of the front lights had been replaced due to collision.  Go to that corner, and remove things.  Odds are very good a bodyman screwed something up there.

In reply to Streetwiseguy :

One of the first things I checked. It wasn't much of a crash, broke the grille and headlight, bent the hood and fender a little. Only replaced the light and muscled the hood straight. Nobody but me has been under the hood of this car for the last 90k miles. 

I like my hair pulled

I did actually laugh out loud when I read that.