There was a lot of input on a similar issue recently. Can I suggest that you review this thread and if you need more help, post a few pictures.

Chris

https://www.diychatroom.com/f7/first-time-soldering-1-2-copper-pipe-681443/

 

Doesn't help. I've re-plumbed my entire house with copper pipe/fittings and brass valves. Something about this is totally different. The solder won't melt, when it does it does not flow into the joint. I believe that by the time I'm getting the joint hot enough the flux has all burnt away.

Picture attached.

 

Before soldering attempts, was the plug a tight fit in the fitting? The solder flows via capilliary action.

Chris

 

Good point, unlike most joints, the plug would not have stayed in the joint if upside down. It stays a little better now after 3 attempts and cleanings.

 

Screw a brass IP cap on it and be done with it.
Or, solder in a short piece of copper pipe and a cap. That's how I did 4 port valves for years. Then you use the pipe stub to help anchor the valve

 

Ya fair enough. I was trying to limit the length of the dead-leg (not that it's that critical) and assumed that the part supplied wouldn't be a huge hassle to install.

 

That plug looks fairly burnt. At this point I’d heat up that fitting just enough to get most of the solder out in liquid form, then sand to get the rest, then make my own plug from a few inches of copper pipe and a cap. Maybe that supplied plug isn’t quite the right OD, so the solder isn’t being drawn into the joint.

If you’re using a regular propane torch on a small fitting like that and the solder doesn’t flow with 15-20 seconds, it probably isn’t going to. There isn’t any point in heating for 10 minutes.

Chris

 

It's just the burnt flux, it'll shine up again, but I think you're right, time to move on.

For some reason the plug cools very quickly, and the shower valve is a giant heat sink. I don't have MAP-Pro, and it's not worth it just for this.