5th wheel unlocks by itself.

I have high hooked a trailer before and it can cause the jaws to close around the kingpin but not lock. If you crawled under trailer and looked at the jaws everything appears "ready to roll". I then set trailer brakes, pulled forward an inch or two and then backed into kingpin with more force. Still jaws would not hold. The mechanic showed me how to fix the jaws. Pull AND HOLD the 5th wheel release handle out for 5 seconds. That resets something. Then back into kingpin and try another tug test. So far it has worked every time I've had a disagreeable 5th wheel. Remember, pull AND HOLD for 5 seconds.

 

If its a Fontaine "no slack" Fifth wheel, They are completely opposite(complete junk), always slack, Had to adjust mine every week since new. I Wish they still made those ole Mack 5th wheels that were indestructible non sliding sitting on Mack Trunions

 

Is that speaking from experience?

 

I always crawl under with a light and make sure everything is good, if not I take it to the fleet shop.

 

I'm always thinking about that happening. I do a couple good tug tests then go under with my flashlight to check.