Hornby King Class with HM7000 Decoder producing sound but no motion.

[Pendragon Sailing]

Here’s an odd thing.

I’ve just obtained a 2nd hand but ‘as new’ King William IV loco - DCC Ready. It runs extremely well on DC; with a lovely smooth motor and drive action, with no issues.
Installed an 8 pin HM700 decoder (in tender) but I’m getting sound but no motion.

I know the decoder is fine as I’ve taken it from an existing loco, and it also works fine on my decoder test-board - indeed I used the test board to successfully upload the King Class sound profile.

However, when installed into the King loco, I’m getting glorious sound by no motion. I’ve tried all the usual things, including cleaning wheels and pickups. I’ve also checked continuity on the 8 pin sockets (female) on the loco’s PCB.
However, I’m still getting sound but no motion. Switched back to DC (replacing the blanking plug) and motion fine, so there doesn’t appear to be any wiring issues between the tender and motor in the loco. All very odd……🫤🤷🏼‍♂️
Any thoughts on other troubleshooting suggestions, most welcome

[Pendragon Sailing]

Problem solved……the 8pin socket on the locomotive was faulty. The pins on the decoder were not making good contact and/or the solder joints to the loco’s wiring loom were  poor.  I’ve replaced the female socket and re-soldered the wires on the loco’s PCB and everything now fine….annoying, but at least I found the solution. 
 

[gilbo2]

Good to read you sorted it. I fitted the 8 pin decoder version a couple of weeks ago and noticed how loose the plug was in the socket so ended up bending the bins ever so slightly to improve contact.