Troubleshooting MasterLock Coupler Lock Where Key Seems Stuck

Updated 07/10/2020 | Published 07/06/2019

Question:

Having problem key won’t turn to

asked by: Harvey D

Expert Reply:

Try shooting some WD40 with a straw into the key slot of the Master Lock Trailer Coupler Lock # ML389DAT to see if you can get it to free up stuck tumblers. Most likely that will fix the issue but if not let me know!

expert reply by: Jameson C

Todd H.

7/6/2020

Hi Jameson, I tried a graphite lock unstick product, but the key still won't turn. Any suggestions other than drilling the lock?

Chris R.

7/10/2020

There's not much else you can do. I would try the lubricating process more than once though. You may need to spray it into the lock cylinder, let it sit for a bit, then push the key in and out to really try to free up whatever is seizing up the mechanism. I would repeat this process a few times before resorting to the drill.