Hey guys I've been working on my 99 Ranger 2.5 5spd. A buddy warned me recently that my tail lights are not working, however both rear blinkers, brake lights, and reverse lights are working. So when I turn the switch for my headlights, they come on, but my tail lights don't. Anybody had this problem before or know some things I could check?

 

Did you check the harness towards the back by the bumper? Maybe the beds been off at some point and a wire got pinched? Just a thought...

 

Confirm function on your front parking lights (corner light, bottom turn lights) as well as your plate lights. They are all on the same circuit. If those lights don't work, there's a main circuit problem. If only the tail lights fail to illuminate, it's isolated to the lights themselves.

Should be obvious, but check the bulbs. Not a bad idea to buy a new pair and stick in. I've seen bulbs that look just fine but are actually duds. It's possible that either both blew at the same time (although unlikely) or one went, and since they work in pairs, the other soon followed before you noticed.

If they still fail to illuminate, you'll need to get a multi-meter. A test light isn't advanced enough for this.

There will be three (or four) contacts inside. Two will be ground, one will be for brakes, and one will be for tails.

Take the black lead and fix it to a bare piece of metal on the frame. Alligator clip leads work great for this. Both can be picked up at harbor freight for little money.

If your multimeter is 'auto ranging', set the dial to Volts DC, marked by a V with one line and a dashed line. If yours is 'manual ranging', you'll see the same label within a given range. Select '20' in this case. It's a good idea to test the meter first on the battery to confirm all is working.

Being careful not to touch more than one contact at a time, probe the sockets and look for 12 volts DC. Your tail lights should be 'on' at this point.

If 12 volts is not found with the tail lights on, attempt to locate the pin used for brake lights. A friend to step on the pedal or something heavy works well here. If the brake light 12+ pin cannot be located in the socket, ensure your meter is grounded and try again. If you can locate the pin, that means the sockets aren't getting voltage.

However, if you find 12+ on one of the contacts for tail lights, that means the ground wire is compromised. Set the meter to 'ohms', (looks like an odd horse shoe) (any range) and look for two ground pins. If you happen to find one pin that does not show voltage and does not have any connection to ground, the ground wire is compromised on that circuit and must be repaired.

Although unlikely, pay attention to how much voltage you see on the tail light pin, if you find any at all. You should see close to full battery voltage. If you see only 4, 6, 8, etc, that means there's some resistance somewhere that must be fixed. Resistance could be due to corrosion or if the wire is frayed.

One last thing. follow the harness from the rear of the truck towards the front. YOu have a 99 similar to mine, so you should see either one or two plugs going into the driver's side floor. Open them up and ensure there is no corrosion. If there is, clean the connection and test again.