Same problem. but on 2003 3500. the left turn signal relay is integral of the fuse block. referred to as PCM. When tapped with mechanical force the relay operates. Must replace fuse block mechanism. So, looks like it's going to be a an expensive fix.
Probably, the original flasher in the tow vehicle is not designed to carry the load of the extra lights on the trailer.
The flashers are in the DS fuse panel, behind that fuse panel there is also a flasher relay that controls the truck and trailer signal lights and the trailer brake lights. To get to the back of the fuse panel you must take the bottom part of the dash off.
The flasher relay in the tow vehicle needs to be replaced with a heavy duty one.
Yes, just like you would anywhere else.
If the turn signals on a car works but the hazard lights do not there may be a problem with the flasher switch. The flasher is located in the steering column, and a damaged unit can cause the lights to stop working.
check fuses under the hood
If I understand the question, you probably need to replace the flasher. First make sure that all of the lights are working since having burned out bulbs will not supply enough load to make the flasher work.
I hope someone answers your question because I have the same car with the same problem.I already had a connector it the car for trailer lights. It used to work & seems to still be working. But when Haul plugged in trailer lights to it, our turn signals stopped working. The connectors from the trailer were real ratty; I wouldn't be surprised if they hooked up something backwards. They also had to run a separate ground wire to get the lights on the trailer working. I think they had the turn signals working at some point when they were hooking it up.Symptoms (all started when trailer hooked up):Turn signals completely dead. No lights, no flashing, no turn indicator lights on dash board.4-way flasher also completely dead.Alternator light on dash & brake warning light on dash both on.Problem same whether trailer hooked up or not.Things that still work:Brake & parking lights work fine on car & trailer. I repaired the connections on the cable coming from the trailer and it seems to be wired correctly. I tested the trailer lights with a spare battery and they light when they should.All fuses visually look good (both the ones next to driver & the ones under hood).UHaul connector installed on car has built in indicator lights (wonderful feature!). Lights come on when they should for parking & brake. But they don't come on for turn signal, which is no surprise.I can't find the flasher (if there is one). I can't find my owner's manual. I can't find any clues or fuse diagrams on the Web. (Google has a lot of strange Russian websites that don't have anything to do with the car-annoying.Help!============================Richard, did you ever find out a reason for this? I have exactly the same problem.rickPossible solutionTry the hazard switch this cuts out the supply to the indicators to prevent overloading the circuitif the switch has gone faulty the indicators do not normally work.
Replace the flasher relay if the lights come on but do not flash.
Fuse is blown light connector is unplugged ground wire on trailer disconnected
Make sure you have a good ground
Try pulling out the hazzard light fuse or hazzard flasher relay.