Hitchweb has put together an article that answers the most frequently asked questions about Trailer Wiring:

Q. What do I do if my trailer has dual bulbs and my vehicle only has one?

A. If the trailer has dual bulbs and the vehicle only has one, make sure they are wired for a 6 or 7 way and use the 118158 reverse converter.

Q. If the trailer light has a license light - is it a left or right?

A. Licence lights go on the left side of the trailer, no license light goes on the right side.

Q. Are 7-pin to 7-blade Adapter available?

A. 7-pin to 7-blade Adapters are no longer available. They are not common in the industry, Ford only used them for 2 years.

Q. Is there a 24V to 12V Adapter?

A. No, it does not exist. To hook up the running lights, change the bulbs on the trailer to 24V bulbs (available from Automotive) and use a 24V Converter.

Q. Are 5-4 Adapters still available?

A. No longer available. You can still plug the 5 prong into the 4 prong, but the reverse (5th prong) will not work.