I would also look up a company by the name of westbar or wesbar. They make adaptors. I beleive that I saw one there. I recently got the a 7 pin to 5 flat adaptor. I got it at the rv place in town.
Before you go to any trouble re-wiring, you might want to call a few RV/Trailer supply parts department. They might have an adapter on the shelf somewere. Just a thought, as I got mine at a trailer supply place in Havasu.
I would also look up a company by the name of westbar or wesbar. They make adaptors. I beleive that I saw one there. I recently got the a 7 pin to 5 flat adaptor. I got it at the rv place in town.
The problem is that the 5 pin connector on the trailer has to have the 5th pin "hot" to prevent the surge braked from engaging, the 5th pin is keyed to the reverse lights.
There is no adaptor for a 4 pin truck to a 5 pin trailer.
The short term answer to your problem is Dan's trick. connect the 5th pin on your trailer to the pin on your 4 pin truck that is controlled by the running lights circuit.
Just turn the plug sideways (perpendicular) so the mated plugs look like an "L" .
Rotsa Ruck
CA Stu
Ca Stu is right there is no adaptor to go that way because you need the wire to release the brakes when backing up. My .02 just get the right plug on the truck then you won't have any problems. In fact wire the seven blade on the truck and get the adaptor to 5 flat. Then you are set to pull any trailor.