I have a 1999 Ford Ranger, and am in need of the electrical schematics
(wiring diagrams) so that I can troubleshooot a problem I have with a
four wire trailer lighting system.
The running lights work, but the turn signals, brake lights, and
flasher signals do not work.
Does anyone know where I can purchase the factory electrical wiring
manual for this Ford Ranger?
Thanks for any help,
You shouldn't need a manual for that. You might however need a volt /
ohm meeter or maybe one of those automotive test lights but I've never
used on of those.
A basic electroincs tutorial: To light a lamp, you must pass a current
through the lamp filiment. So if you have a battery and a lamp, you
must hook up the filiment of the lamp accross the two battery terminals
to allow the current flow. This would require two wires, right? Now
think about the battery being mounted in your truck. One of the two
wires goes inside the cab and is connected to more than one place. One
place is the turn signal handle which is a switch. another is the brake
and another is the light switch. Each of these switches have the
ability to connect another wire to the one from the battery. These
other wires are the ones that go to the trailer. They also happen to go
to the back of your truck and connect to the tail lights, turn signal
and brake lamps of your truck. All of these lamps also need that other
wire that goes all the way back to the battery. That wire is called the
ground. It is simply the return path to the battery.
A typical trailer has two turn signals, a tail light and a brake
light. All of these lamps need a ground to work. So that would be 5
wires total required for those lamps. If you only have 4 wires, maybe
you don't have something i listed. The trailer lamps get their ground
through the trailer frame. Near the front of the trailer there will be
a wire attached to the trailer frame with a screw that goes to it's
connector that plugs into the trucks connector. This wire is required
or the lamps will not light or stay working correctly. Someone might
try to rely on the trailer hitch attached to the trailer ball for
providing the electrical connection for the ground. Wrong! That's no
Before you start on the trailer, make sure you have a good grond on the
trailer connector. The Trucks ground connector may be attached to the
truck frame as I described the trailer's ground. If so that is fine. To
really "know", you need a test lamp or a meter. A test lamp could be
someone else's trailer with known working lights. Using either a light
or a meter you must be able to measure 12 volts between the connector
ground pin and one of the other pins used for lights, brake or turn
signals. Once all of these signals are working, then proceed to troble
shooting the trailer lights.
Start by plugging in the trailer lights. Now goto a lamp socket and
determine if the 12 volts is getting to the connector or not. Wires
don't tend to go bad so, a wire has either been broken because it
snagged on something or the lamp is bad or the lamp has a bad
connection at the socket. I'd bet on the last one. There you go. A
trailer light manual. Good luck..
Walmart sells an entire light kit for about $29. That's two rear lights
with all lamps mentioned and 2 side running lights and of course it
comes with new wire that includes the trailer connector.
For the manual if you want a factory manual then go to the dealer. There is
probably a phone number in your owners manual where you can order a manual
in book and/or CD by phone or online.
If you want to save about $100.00 then get a 3rd party repair guide such as
Haynes or Clymer from an autoparts store or online.
I had problems with my trailer wiring and found that my custom bumper/hitch
does not provide a sufficient ground through the hitch/ball. I have to take
some jumper cables and clamp from the truck frame to the trailer frame in
order to get things to work.
Check all your fuses in the truck. On my explorer (yes also a Ford) there
is a seperate fuse powering a set of relays that operate the trailer
interface cable. I can hear them click only when a trailer is hooked up.
If you installed the cable and connected the trailer and there was a short,
you will have blown that fuse.
If you wired your own harness, you still may have blown a fuse but it should
knock out the lamps on the vehicle as well. Check the continuity of the
trailers connector from each wire to the common ground. You should see bulb
resistance not a short and not an open.
I got so into trailer wiring I assembled a cheap light tester,
basically all the trailer lights on a short cord I could plug into the
towng vehicle. Makes troubleshopoting easy.
Found the bad towing vehicle ground fast!
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