DazedNconfoosed

I have read countless articles, posts, etc about this type of issue, but to date, nothing has worked. Tail lights, turn signals, hazards (one filament of brake bulb lights up), rear license plate lights all work. So, here is a list of what I have done already:

- Checked bulbs
- Checked the #42 fuse under the hood
- Checked for breaks in wires from brake switch to brake light sockets
- Verified grounds are all OK (and other lights work, so...)
- Checked brake switch (for continuity, as described in owners manual), and even tho' it checked OK, replaced w/ new switch (AutoZone), then back to the original
- Ran 12 volts directly to green/white wire from switch; bulbs lit up
- White/green wire to switch has voltage: stuck straight pin into wire, then tested w/ volt meter. Showed just under 10 volts, so not sure if not a great ground to the negative meter probe, or similar with the positive probe, or if the battery was running low at that point... Plus, I'm not certain which wire, exactly, is supposed to carry the voltage TO the switch.

And... I'm lost.

I'm getting too old to be contorting myself under the dash of this thing, and I cannot for the life of me figure out what the problem is. Anything other than hauling to a shop, anyone have any suggestions? It's old, 300k + miles, rusting... but it runs, gets great mileage still, and I really can't afford to get rid of it just now.

ezone

At the brake light switch under the dash
white/green comes from fuse 42 (engine compartment), carries battery power into the brake light switch
green/white takes power exiting from closed switch contacts, carries it to the lights.
The switch connects those two circuits.


All easily checked.
Use a paper clip to connect the green/white and white/green together at the switch. Got brake lights?
If no, measure voltage on the exposed paper clip, it should read battery voltage. If not, there's a problem. 10v with no load is low, and I bet measuring it loaded would show close to zero volts.


Does the horn work good? (it shares the same fuse)

White junction connector, 20 cavities, behind cruise control unit, drivers kick panel area.....may have bad or corroded connections between the white/green wires there.

DazedNconfoosed

Thanks for the reply! Also, the suggestions. Here's where I am: I used the paperclip as pointed out and yes, there is battery voltage at the wh/gr wire. No, I still did not have brake lights when connected to gr/wh, AND voltage dropped to zero (plus, the battery was drained when I went out this morning after a day off from the car yesterday).


Yeah, about the horn.... I forgot to mention that no, it does not work. But it is the horn that does not work; verified w/ direct voltage to horn and nothing.

I don't see any corrosion in or around ANY of these wires or connectors. So... how to run down the white/green wire from this point? I unbolted the fuse box under the hood; no immediate sight of broken, crimped, corroded wires prior to entering the taped section of the harness.

Again, I really appreciate the input!

DazedNconfoosed

Also, FWIW, I was back under the dash looking around -- not touching anything -- and the power door locks started activating, by themselves. It was erratic, in that when I would do the unlock from the driver's door, sometimes it would activate, sometimes it wouldn't. Even when it wouldn't, most times (but not all) it would work when I hit the lock position.

ezone

ok so you lose power once the circuit is loaded. Is the fuse #42 good? (this is why I mentioned the horn shares the same fuse, if both the brake lights and the horn don't work it stands to reason the fuse may be bad)
If not, replace it and recheck.
IF fuse is good, then it seems that you'd have a poor connection somewhere between that fuse and the brake switch.
You've got a lot of harness from the engine compartment fusebox to the 20 cavity connector under the dash I described earlier, then from there to the brake switch.
This may be a separate problem. I'd use an ammeter (milliamps) to check drain current with everything off and keys out.



Horn doesn't work when you connect it to battery...ok...but does the wire supply power to the horn?
This is why I mentioned the horn shares the same fuse #42, if both the brake lights and the horn don't work it stands to reason the fuse may be bad. Anyway....


You have the paper clip in the brake switch connector and it measures zero volts.... now go the harness coupler in the drivers kick panel (described earlier) and find the same white/green wire, backprobe both sides of that wire in that coupler to see if the power was lost within that connector.....and if both show zero the break is somewhere between that coupler and the fusebox...


It's usually about backprobing along the loaded circuit until you locate the point where the voltage changes.....could be a long process and if you try to stab through the insulation you may damage more of the suspect wire in the process . (it could take years for a nick in the wire insulation to let enough water in to cause corrosion and rot the wire open, your problem sounds like that's what may have happened. The problem is pinpointing where that break is.)


You'd probably have to find the specific white/green wire at the fusebox and follow it into the dash. Or , if one figures out where the bad area is..
you could overlay a new circuit (wire) from fusebox to the dash to bypass the bad area



Hmmm... I've got cool tools just for finding stuff like this...an RF signal generator and receiver lets me follow a wire around the car and wherever I lose the signal is where the break is.


For more ideas you could google 'how to find a break in a wire' or some such, see how an electrician might locate a break in a hidden wire you can't see in drywall, or in a bundle of other wires.





Broken wires in the door jamb harness, they can make and break connections as you swing the door?

DazedNconfoosed

I did search for locating breaks in wires and some of the necessary tools; thx. But all things considered... inaccessible (essentially, w/o tearing out the dash, and likely more) as this is in the main harness, I went with the option to just overlay with a new circuit. It works! I have brake lights!!

I haven't even bothered with the power door locks -- or horn -- yet. Well, I did buy a new horn, but of course it doesn't work as the circuit is now. I want to make sure it doesn't drain the battery overnight before I approach those.

Thanks so much for the advice! It was very, very beneficial.