I have a 2001 Ford Ranger with a strange issue with the brake light/turn signal. It doesn't work. I've replaced the bulb and that didn't solve it. I swapped the bulb to the other side to see if it worked at all and it worked fine. I've swapped the bulb socket and that didn't change anything either. I check the voltage with a multi-meter and the socket gets 12 volt when it should but it only gets like half an amp when it should get around 7-8 amps. I've replaced the fuse and that didn't fix the issue either. I'm dumbfounded with this issue. Oh and also the parking light still works on the same bulb so it's probably not a ground issue. Any help would be appreciated.

 

Multi-function switch(turn signal stalk) is most likely the issue

The 2000 and up Rangers use a "2-wire" tail light system, this means brake/turn share one wire to the tail light, one wire to left side, one wire to the right side, 2-wire system
These wires comes from Multi-function switch

In 2001 Ranger
Dark Blue/white stripe wire for Left turn/brake
Brown/yellow wire for Right turn/brake

First thing to check will be under the rear left side of bed where the wires come from the front inside the frame rail
You are looking for past attempts to splice in Trailer light wires, lol, people can butcher wires when tying to add trailer light hook ups
You can unplug the connector and test the above wires with turn signal or 4-ways ON to see if the 12v is making to the rear on the side thats not working

Then go to the cab and remove the clam shell covers from steering column to access the Multi-function switch
Unscrew the switch and unplug the connector

Connector will have a Dark Blue/ORANGE stripe wire, this wire has 12volts all the time, not key on/off, all the time, its for Flash to Pass
Use a jumper wire to hook the Dark Blue/orange stripe wire to either rear turn/brake wire and the bulb on that side should light up if the wire and bulb are good

If wire and bulb are OK then problem is in the Multi-function switch, replace it

 

Does the Ford Ranger have trailer light hookups as a stock package? Because I know it has a set of them dangling under the bumper because the plastic fitting is worn out.

 

Some Rangers came with the trailer plug from the factory.

If your truck has these fuses and relays, it's factory trailer wiring.

In cab fuse box
Fuse # 3 = 7.5 amp - Right Stop/Turn Trailer Tow Connector
Fuse # 7 = 7.5 amp - Left Stop/Turn Trailer Tow Connector

Under hood fuse box
Fuse # 30 = 15 amp
Relay 56B = Relay