Trailer Light stay on when swithc off car

[cannon253]

Hi,
I have a 2008 Subaru Forester and a Hunter Fat Shadow.
I picked up the trailer and all light checked out and brought it home, about a week later I hooked up the car and the driver side brake light was on, I took it to the RV delaer I bought it from and the found the trailer light all wire proberly so I took it to Subaru and the said the wire haness converter was bad so they replaced it. All the light worked correct wehn I got it home but wait, we took off on Friday for our first time out and all lights worked fine, we headed for home on Saturday again all lights worked fine. Stopped at a park and had lunch, agian all light worked fine left the park and drove to a friend about an hour away and when we left there house lights were working fine. When we got to a resturant for dinner I parked the car and noticed all the running light were still on. I had to unplug the trailer to get the light to turn off. When we left the diner and I plugged the lights back in the were still on so IO checked and the break light worked along with the signals, I don't understand what is going on. I have constant power on the brown lead out of the pigtal from the converter. Any suggestions??? Confused.

Jerry

[halfdome, Danny]

I may be way off base here but try this.
Check all your connections car & teardrop plug for a single strand of wire that may be touching another terminal.
I had one, it gave me nothing but headaches until I found it. Danny

[cannon253]

Hey Tahnks but I went thru all that today.
From the wire harness of the car the brown wire is always hot.

[bobhenry]

Sorry to tell you this but I am all but certain you have fried yet another converter. These things are not real tolerant to high draws or dead shorts.

Use a ohm meter and check for continuity between the tail light (Brown) wire in the harness and the ground ( probably the frame) Do this without power. The ohm meter adds a small current and measures what comes back It should be zero but I will bet you will get a reading. You will need to look farther than just the tail lights might be a clearance light a license plate light even just a wire pinched thru the insulation. If you have a continuity reading disconnect the light one at a time and test after each until it reads zero when this happens you have found the offending circuit. You can test hot with a battery and jumper cables and feel for warm wires but it's kinda iffy and not real scientific.

[dreadcptflint]

This might help. I had something similar happen to me. I also noticed a rattle with my plug. (It is a seven pin). I took it apart and low and behold there was a nut that had fallen off and conecting the circut causing lights to stay on.

[TENNJIM]

Probably the new powered converter is gone. They are not very reliable. Pull the fuse on the tap from your battery to the converter, the 12v on the brown wire should go away. If so, The converter has failed and is running the 12v to the brown wire at all times. You can run the checks bobhenry suggested to try to keep from frying another one. However, it could just be a bad converter. I am on my third one.

Jim B / Utah

[cannon253]

Thanks for all your help I will let you know what I find.

[wannabefree]

Long post warning, but this got me thinking.

I'm assuming you have a 4 wire trailer connector and a battery in your trailer. If not, everything below will still apply, but there could also be a brake wire (blue ir I remember right) and a charge wire (maybe red or black).

This is a weird one. Here's why: power has to come from somewhere. Most tail light converters do not have an independent power source; they don't connect to the car's battery. What they do is scavenge power from whatever light comes on and steer it through some diodes and transistors to your 4 wire trailer system. When the lights are off, there is no power getting to the converter, so the lights can't be on! Unless... we'll get to that.

First, check your car wiring. Here's how:
1 Get a cheapo multimeter. $3 at HF, $15 at Ace.
2. Start with the car, disconnected from the trailer. First, set the meter to Ohms and stick one lead into the pin connected to the white wire and the other lead to the car's frame. You should read less than 1 Ohm. If not, you have an open ground and it's probably in the converter or the connection to the converter.

3. Turn on the headlights. Set the meter on Volts, something higher than 12V, say 20V. Connect the black lead to the white wire and the red lead to the brown wire. You should read something in the range of 12V. If not, move the black lead to the frame. Still nothing? Blame the converter. Got something? Go back to step 2.

4. Turn off the headlights and turn on a turn signal. You'll probably have to start the car to get the signal to blink. Now look for voltage from green or yellow to the white wire. I forget which is left and which is right. But one will have voltage sometimes when the signal is on and none if the signal is not. Don't expect to read 12V with a digital meter, they take too long to settle out, but you should read something; the reading will bounce around. Or use a test light. Do this for both yellow and green, right and left signals.

5. Turn the headlights back on and repeat step 4.

If everything checks out, it's not your converter. Unless...
Remember, power has to come from somewhere. Look under your car for a wire run from the battery (or fuse box) into the converter that looks like it was added by the dealer. If you find that added on wire, turn everything off, connect the black lead of you meter to white, and move red to the other three wires (brown, yellow, and green) and look for a voltage. If you read near 12V on any of them, blame the converter.

If there isn't that extra wire, the only other place for power to get to your lights is from your trailer's battery.

Now go to the trailer. Set your meter back on 20V. Don't hook up to the car. Connect the black lead to the white wire on your trailer and measure voltage on the other wires; yellow, brown, and green. If you measure anything greater than say 200 mV (0.2V) you have a short between your trailer's battery circuit and your trailer's light circuit. This could also possibly blow a converter. Tracking that problem down should be a job for the guys that sold you the trailer. Take it back and show them the problem with your meter. Otherwise they won't believe you.

Good luck.

[cannon253]

Hey thanks for your input on this problem.
1. the converter talked about is stock wiring harnes from Subaru with this little black box they call a power converter. It has approx 8 leads in including battery and 4 leads out white green yellow and brown for the standard 4 flat plug.
2. I found out that when there is a shorted light on the trailer or to much resistance the converted will blow.

I ended up taking it to an Auto electrical shop to get fixed, it ended up being a dead shorted light and the wiring changeover the seller did had to much resistance and was also replaced. This all should take care of the problem and I will find out when we take our next trip.

Jerry

PS the stock harnes with power converter from Subaru is $100.00, I found some on line for under $50.

[bobhenry]

Sorry to tell you this but I am all but certain you have fried yet another converter. These things are not real tolerant to high draws or dead shorts.
Use a ohm meter and check for continuity between the tail light (Brown) wire in the harness and the ground ( probably the frame) Do this without power. The ohm meter adds a small current and measures what comes back It should be zero but I will bet you will get a reading. You will need to look farther than just the tail lights might be a clearance light a license plate light even just a wire pinched thru the insulation. If you have a continuity reading disconnect the light one at a time and test after each until it reads zero when this happens you have found the offending circuit. You can test hot with a battery and jumper cables and feel for warm wires but it's kinda iffy and not real scientific.

TAH DAH !!!!

[dh]

I put a 4 pin on my utility trailer incase somebody needed to barrow it and used an adapter for the 7 pin on my TV. I had all kinds of problems with it. Lights would work fine, a few miles down the road my right turn/stop was controlling the running lights, hit a BIG bump, it would correct itself for a few more miles. I ended up cutting off the 4 pin and putting on a 7 pin connector.

[wannabefree]

So I wrote all that for nothing??!!!

[vrodjason]

So I wrote all that for nothing??!!!

Not for nothing at all. Very good Info!

[TENNJIM]

So I wrote all that for nothing??!!!

Actually, that was very good info and helpful. When a converter is required, a powered converter is now being used on car systems that cannot handle the extra current draw of trailer lighting. A wire is run from the battery through a fuse and then to the converter installed in one of the taillight compartments of the tow vehicle. So, there is 12Volts going to the module at all times.

Jim B / Utah