kiacker wrote:Arggh! OK, I went thru all the grounds & ground down the paint at each attachment site to the frame. I then wired them all together (since it is a bolt together frame) & attached them to the ground on the trailer plug - no change.
The tow vehicle is an 89 Ford Ranger with a Hoppy wiring adapter that connects in to my current wiring & has an adapter/converter for the 4 pin trailer connector. The truck uses a single bulb for stop, turn, and park. The trailer has no turn or brake signal when truck lights are off. When truck lights are on, turn signals then work but still no brakes. What a frustrating problem!
Lisa
Hi Lisa,
You're working on two vehicles at once which multiplies the troubleshooting by many orders of magnitude. Divide and conquer! That is...disconnect the trailer from the tow vehicle both physically and electrically.
Step 1: make sure the the connector on the tow vehicle is working properly. I'm assuming you have a flat-4 connector, right?
- The male pin that sticks out is ground (white)
- The first hole next to that is the running lights (brown)
- The next hole over is the left brake/turn signal (yellow)
- The final outside hole is right brake/turn signal (greeen)
I find it easiest to use a test light (they're cheap) [Well really the easiest is a connector tester which just plugs in and they're not expensive but most of us don't have one.]. Turn on your parking lights (running lights) and connect the alligator clip of the test light to the male pin (which is ground). Insert the test light probe into the hole next to the pin (the running lights) and it should light up. If not there's a very good chance that the white ground wire on the truck side is not grounded. Try clipping the alligator clip to a (clean) metal part of the truck chassis and try that first hole again. If it works it's definitely your truck-side ground wire.
Assuming the running light circuit is working go turn the key to the "on" position and turn on your left turn signal. Now (with the alligator still on the ground in) go insert the probe into the second hole...the test light should flash. Then go and switch on the right signal and test the last hole...the test light should flash.
If all is good with the truck you're done there. Don't forget to turn the ignition switch back off. Ah...we didn't check the brake lights. Well, that's because if the turn signals work, unless the bulb filament is burned out or there's a fuse blown under the dash, if the turn signal works on that side so does the brake lamp. If you have someone that can press the brakes then you can check them too. Clip onto the male pin for ground and while the brakes are on check the second and third holes...both should light up.
If the truck was ok it's time to check the trailer. The easiest way to do this is with a battery (any small 12-volt will do). I use a couple of jumper leads with alligator clips at both end and, IMPORTANT, an inline fuse (5 to 10 amps will do) in the positive lead. If you have a short in the trailer wiring you don't want to find that out by melting one of your jumper wires (especially not when holding it!).
The trailer connector is just the opposite with regard to the pin-to-hole population. With the fused lead clip onto the positive battery terminal then clip the other end onto the first pin (next to the hole), this is the running lights. Now clip the ground jumper to negative terminal on the battery and the other end to the hole (I just insert one side of the alligator jaws into the hole and the other side is outside holding on). All the running lights on the trailer should come on (if you have really bright taillights the bulbs are inserted incorrectly and the brake filaments are energized rather than the taillight filaments).
If the runnnig lights don't come on then you have a bad ground. Move the jumper from the hole in the connector to the frame. If the lights come on it means the wiring harness is not getting a good ground. If the lights still don't come on you need to check their individual ground to the frame.
Next move the positive lead from the first pin to the second; the left turn signal light should come on...and it's the only one that should be on and it should be bright.
Next move the positive lead from the second pin to the third; the right turn signal light should come on...and it's the only one that should be on and it should be bright.
If you've got both the tow vehicle and the trailer working at this point reconnect everything and all should be good.
I thought the '89 Ranger was a Mazda pickup? Most Japanese cars have separate turn signals (not part of the brake system). Are you sure this isn't the case on your Ranger (I don't know them at all)? If they are indeed separate you need a taillight converter (available at almost all auto parts stores).
That was a lot of typing, and probably reading, but doing it that way I can test and diagnose a vehicle or trailer problem within 5 minutes because I'm not trying to work with both units at the same time.
Good luck and best wishes!