It sounds like you might have a open circuit on the fast flashing side. Maybe a bad bulb, or a bad connection in one of you light sockets.

 

Well, I replaced all bulbs, problem still exist. Connection is good because I rewired it because when I purchased it 3 months ago, I bought it w/o a bed. Purchased a bed and put in new wires. Open circuit? tell more

 

If you don't have a good ground that would cause an open circuit situation. It just means that the circuit isn't being completed. Bad ground, bad bulb, bad connection, would all mean that the circuit isn't finding ground. If you wired the lights yourself just check your grounds, it could be that simple. If you wired into the trailer cicuit for your lights it wouldn't cause a Lamp Out warning on the dash. I'm used to working on Fords here at work and when the flasher goes crazy on those, 9 times out of 10 I know it's a bulb. I forgot that we have Lamp Out indicators on our 3rd gen. dashes, though. Another thing is, if you have LED bulbs it can cause fast flashing because they don't create enough resistance to heat up a flasher. This causes the same open circuit symtoms. It's complicated. Oh, we had one truck (a Ford) that was shifting very eratically and would never go into overdrive turns out it was the third brake light being out. Go figure, electrical sucks.

 

Thanks GT I will look into that this weekend. I need to make sure the ground is a good one. Thanks for your help. Its weird how one simple thing like the third lite can cuase the trans to not shift correctly