Trailer lights question

[Polarity]

I had my lights working no problems last time the boat went out, this time when I turn my lights on the running lights are on but no brake & and no turn signals... the turn signal light and right side of the brake/running light is on constant with the running lights. I put the adapter in but not the trailer wire plug and tested at the adapter.. the metal prong that sticks out lights up ... none of the other 3 units work.. neither brake or turn signal.

I checked the fuses and I don't see any fried
1998 Ford Expedition

[REEL TIME]

Im a little confused at your description,but here goes.On a flat four prong plug which is most common the exposed pin on the tow vehicle side is ground (white)next is the running lights (brown)followed by the left turn and stop (yellow) and finally the right turn and stop (green),a constant flow to the exposed pin would indicate a short in your truck harness,follow it back to your main and check the connections and spray with electrical cleaner as needed.if your truck has the factory trailer package you may have a set of fuses under the hood on either fenderwell (mine were on the driver side)check them.If it was wired from the rear plug could be its gone bad due to corrosion you can get replacements from auto stores that plug right in.How are your trucks lights ,if okit should be a simple fix.If your problem is the trailer just trace out the wires useing the colors above and it will probably lead you back to the tail light assembly.
Good luck Hank

[Polarity]

Truck lights are fine, I think the easy fix since the fuses are good would be to unplug the factiory assembly and replace with a new aftermarket and see where that gets me, I saw them today for about $25.00 .. but yes constant power to the lights no brakes, no turn just running lights

[REEL TIME]

Ok truck lights good,before you pull apart the harness check the plug with a test light get the ground from the hitch or anything but the plug,then stick the point into the first hole ,should be running lights then try the next with your turn signals on see what you get .Is your plug a flat four or do you also have the round pin type my expeditions had both factory wired with the tow package (2002,2004)if that all checks out then start at the trailer plug and work your way back.Make sure you open the round plug up and look inside at the connections if you have that style water tends to get in and sit on the bottom causing the lower wires to corrode could be why both of your signal/brake lights are the only ones out,i know this sounds stupid but check the bulbs in the trailer who knows keep me posted Hank

[slickster]

You have a bad ground and the current is feeding back...pull the bulbs and clean the sockets first...Mick