Dead Battery - Jump Start - White Smoke!

[kjmclark]

This shows the soldering problems I found in the dimmer module. So middle toward the top is the spider-legged chip that's the brains of this board. Just lower left is a little resistor or something that's black and looks like it has 000 painted on it. Just to the down/right of that are two little silvery blobs that look kind of mushroom shape. Up and to the right of those two is another one that looks like a shiny pyramid. All three of those should look like the last one. When I soldered the two mushroom-shaped ones down properly, I suddenly got proper voltage on one of the lines that was dead before. I think this happened a long time ago - not related to this problem, but I fixed it anyway.

 

[kjmclark]

Next, this truck has five relay boxes! I could hardly believe it. There's the main distribution box under the hood with a few relays there. There are two smaller boxes by the radiator on opposite sides of the truck. There's an extra one by the main distribution box for the 4wd system. Finally, there's another one under the dash:

This one has the parking light relay. To find it, you want to lay on your back on the floor mat, with your head hitting the gas pedal, and look up and toward the cable for the gas pedal. The spring at the very top of this picture is at the top of the gas pedal. The box itself is a rectangle, but notice that the back of the thing is narrower on the left and gets wider to the right. That's the only way you can match up with the diagram for the relays inside.

 

[kjmclark]

Last one. This is a picture of the inside of that box:

According to my handy-dandy Ford manual, those relays are:
All Unlock Relay / Starter Interrupt Relay
All Lock Relay / Interior Lamp Relay
One Touch Down Relay / Battery Saver Relay
Parking Lamps Relay / Electric Shift Relay
(so upper left in the picture is 'All Unlock Relay')

So the relay I needed to test was lower left in this picture, and yes indeed, with that relay pulled, I could switch the lights on without blowing the #3 fuse. The lights didn't come on, of course, because without the relay, they didn't get any power.

 

[kjmclark]

So, somewhere after that relay, between there and the actual bulbs, there's a short. I'm betting it's in the front somewhere. Unfortunately, to diagnose that I'd have to yank one of the three great big connectors under the main distribution box under the hood and test there. I can't figure out how to get those off, and I'm a little afraid there's a tool for that and I'd end up breaking something important. Besides, that would only tell me which light has the problem (assuming it's in front), and I'd still have to cut open the wire covers to find the problem. I'm thinking at this point it's not something I should be messing with.

If I knew where the darned S130 crimp was...

And having looked under the hood lots now, the reason I didn't connect the negative cable to the block is, like I said, there's no part of the block visible there. The alternator in the 4.0L is about a foot and a half away. My cables wouldn't have separated that far. I need to cut the positive and negative (down the middle of their joined cables) so I can jump the truck in the future. The closest thing that I might be able to reach would be the AC compressor mounts. I still need to separate those cables!

 

[RonD]

You can clamp both jumper cables to the battery, that is not an electrical issue, it was a safety recommendation to clamp the last cable to something away from the battery because of the possibility of hydrogen gas near the battery, and the last cable would spark and ignite it.
Newer batteries don't vent much gas like the older "pop top" batteries.

 

[kjmclark]

Right, and really, chances are good I'm not going to remember to change those cables, and I will just clamp to the battery post clamps. Getting this wiring problem fixed is likely to cost a small fortune now, since I doubt I can get anyone other than the dealership to work on it, and they're going to charge an arm an a leg to tear into those wires.

 

[Mark_88]

Wiring isn't too difficult to do...what I usually do is go to a junk yard and tear into a similar vehicle...make the mistakes on something that is already trashed and harvest what you need...sometimes it takes more than one vehicle to get what you need but the learning experience is more than worth a few hours of your time...

Strip out the seats and dash...and believe me the dash is quite complex when you don't know what the heck you are doing...but then it makes sense and you're on your way...

The guy that sold me the 96 had to replace the heater core and said the dash comes out pretty easy...well, I've spent about 4 hours picking away at it and I can't see how he found it easy...but I'm almost there and it is making sense now...but there is a rats nest of wires under the dash...and they all come out easy enough...

I'm pretty sure those connectors are just bolted in place with a 10 mm socket...but I haven't actually got that far because I wanted to remove the dash before I start yanking harnesses...from the images you posted I couldn't see anything that would be too difficult to replace and if the harnesses all plug into the main power feed at the firewall and are separate then the job is pretty easy to do...but, again, you probably need to pull the dash off to get at everything...

If you have a junkyard in your area I'd go there first before ripping into your truck...pick up the whole harness for the alarm system now that you know what it looks like and just reverse what you did on your vehicle...

 

[kjmclark]

Good point. I need to start getting to know my local junkyards. What do you say to them? "I want to take apart the dash on a late 90s Ford Ranger to see how it's put together"? Would they want to make me buy something to do that, or are they happy to have someone else do the dis-assembly for them?

 

[RonD]

Just say you need the wiring harness, which you do, lol, and start disassembling, if it doesn't match yours..........well maybe next time
And heck if they don't want too much it may be easier in the long run to swap part of the harness.

 

[Mark_88]

Good point. I need to start getting to know my local junkyards. What do you say to them? "I want to take apart the dash on a late 90s Ford Ranger to see how it's put together"? Would they want to make me buy something to do that, or are they happy to have someone else do the dis-assembly for them?

The ones I go to don't require any input...unless you are looking for something that may have already been harvested...and they sell many items at considerable markup for their time...like $75 more than if you take it out yourself...

Guess it depends on the yard you go to, but I think they appreciate it when someone does the work for them...as long as you don't totally destroy parts that they can sell they won't mind usually how long you are there...just don't get yourself locked in overnight...lol

 

[kjmclark]

Looks like this is now an intermittent problem, and I'll probably be trying the junkyard route this spring. I put it into the dealership, figuring they could read any other trouble codes at the GEM, or whatever, have the tool to pull the connector and test the pins, etc. I tend to avoid the dealerships, even though ours are supposed to be pretty good, because I figure they're going to want to replace half the truck with OEM parts every time.

So what did they find? "We just put in the missing fuse and the parking lights work fine."

But, every time I did that, I turned on the lights and pop the fuse was blown. "No, we had them on for a good while and they were on, no problem."

So, somewhere I jiggled some wires just enough for the gap between a pair of cooked wires to be too big for an arc to jump. And a few weeks from now, I'll be driving along and they'll black out all over again. Come to think of it, I'll have to keep a supply of those fuses, and see which set of wires I have to jiggle to make them not blow. Seems nutty, but it's probably going to be as fast as going around the truck with my voltmeter.

 

[Mark_88]

Junkyards have millions of fuses...there's enough there to start your own fuse store...I usually take a couple of the bigger ones while I'm looking for something else because they don't care...but you could grab relays ($20 a pop) if you need them...or good to have a few as spares...the JY might charge you $2 for those but only because they contain valuable metals...or something...