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1999 Ranger 2.5L rear light electrical problems


BeatUpPick'emUp

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Hello!

I have a 99 Ranger with lighting problems in both taillight assemblies. This truck has three connectors in each taillight assembly: one for a single filament turn signal (two pins), one for a dual filament brake/park light (three pins), and one for a single filament backup light (two pins).

The problem began wih an intermittent rear "park" light malfunction, where the "park" lights (what I grew up calling taillights but what Ford seems to call Park Lights) would not come on sometimes. That progressed to the rear park lights not working at all.

The next symptom was the signals operating at double speed when I stepped on the brake pedal. Initially, I observed that when activating the brakes with the signals simultaneously, both the brakes and the signals would flash. Running the hazards produced the same result.

And now, running the hazards will light up the upper (middle) stop light. The remaining bulbs flash weakly, unless I open the circuit by removing both brake lights and/or both rear turn signals.

The backup lights do not work.

The only brake light that lights when I step on the pedal is the upper (middle) stop light.

The only rear lights that work properly are the license plate lights.

I crawled under the truck and started by wiggling the 6 pin connector (well, I think it is an 8 pin connector with only 6 pins populated) to see if that would make the lights work. It didn't. Then I noticed that above the connector, there appears to be evidence of splices in the harness. It's hard to get at but it has what look like blue butt splice connectors (not sure how many) all taped up with elecrical tape. It doesn't look like what I would expect from the Ford Factory. And when I look between the tailgate and bumper, I think I can see some electrical tape on part of the harness that goes from the six pin connector over to the passenger side.

I disconnected the rear taillight harness from the harness which heads forward and checked each taillight assembly wire for continuity. I ohmed out each of the pins from the connector on the driver's side under the tailgate to each of the pins on the three connectors in each taillight.

I found that none of the six ground pins (black wires) have continuity (as expected from the behavior above). All six connectors are ungrounded.

I also found that my +12V pins (brown wires) on the "park" lights do not have continuity either.

So, I think I must have a couple of broken wires. The thing is, it seems to be in the section that runs in a small channel above the spare tire well and underneath the bed. And it seems like, with the connectors on the harness larger than the channel opening, there is no easy way to remove the harness from the channel to check and repair the (suspected) damaged section.

I have searched and I can find no description of how to get this section of wire out. I imagine I could cut the connectors off each end and maybe pull the harness through the channel, but I am hopeful somebody else out there has dealt with this harness and can give me some guidance. I don't want to introduce unnecessary splices.

Is that taped up group of splices a factory splice?

Is there a way to easily get at this harness? A difficult way?

This is pretty urgent as I have everything apart and need to get it up and running ASAP, so your help is appreciated.
 


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4x4junkie

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Indeed what you describe sounds like an open ground circuit.

Unless the wiring is routed differently on a '99 than on my '94, you should be able to disconnect the taillight harness from the vehicle harness and finagle it out of there (it's secured with plastic push pins into the bed and or frame). No, that does not sound like a factory splice, my guess would be a previous owner hacked up the wiring for a trailer light connector.


Welcome to TRS :beer:
 

ericbphoto

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I agree with 4x4Junkie. Someone has messed with your wiring and that is most likely where your problem is. You should be able to work the wiring out of it's hiding place to work on it.

But, if it comes down to it, you could lift the bed high enough to get easier access. On my '93, it's only 6 bolts. But they may be rusted and very tight. You will need a good quality torx socket (if you have the same fasteners as mine) and a breaker bar, possibly with an extension handle. It could help to crawl under the truck and spray the bolts with penetrating oil, too. Once loose, the bed is light. You could lift it up and place a piece of wood (4"x4") on the frame to prop it up while you work.

I would recommend replacing the butt splices by;
  • strip the wires at least 1" on each side of each connection
  • slide a piece of heat shrink over the each wire and slide it back far enough to stay cool while soldering
  • twist the wires together the way they need to be connected (verify they are matched up properly)
  • solder each connection
  • *optional step - coat each connection with a bit of silicone caulk for waterproofing
  • slide the heat shrink over each connection and shrink it
  • put everything back in place
 

BeatUpPick'emUp

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Thanks guys!

My suspicion was also with the splice job. To me it looks like the wrong size butt-connectors were used (they're blue, which I think are for 14-16 AWG, and I think the wire gauge in the harness is 18 AWG).

To avoid dealing with those splices, I just picked up a harness from a guy parting out a 99 XLT locally. The bed was already off and the plastic clips loose.

Looking at the location of all the harness clips, I'm not sure how I'll be able to pry them all out on mine. It looks like there are a couple of clips that are in a pretty tough spot to access from underneath. I wondered if I might have to raise the bed, though for me that means removing my rack and removing my bed liner. Oh, and since this is a New England truck that spent much of its life in New Hampshire, it means lots of PB Blaster I am sure. I was (am!) hoping to avoid that.

It's pouring down rain and I don't have a dry spot to do this, so I aim to get it done tomorrow.
 

BeatUpPick'emUp

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I got the replacement harness installed. I wasn't able to get it in the channel that the old one was in; I simply zip-tied the replacement as near to where original was as I could get it. I would have had to either remove the bed or possibly just remove the bumper to get the replacement in the original location. However, before we bought it this truck had work done to the rear frame (new england salt!) because of rust and after the frame was worked on, they sprayed it down with something like POR-15. I decided this meant trying to get the bed bolts free would be a long job, too long for the time at my disposal.

It turns out the splices weren't to add in trailer wiring. The harness had been cut and all wires spliced back in; I am guessing it happened when the rear frame work was done. I am confident that this is where the failure was.

Lights all work now.

Thanks for the help.
 

ericbphoto

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4WD
Total Lift
6"
Tire Size
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My credo
In theory, theory and practice are the same. In practice, they are different.
Excellent!

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