Pater C -
11-14 amps is too much, so there may be a problem. Unless the Never-Adjust Brakes are different from other brakes (I don't think so), each brake should draw around 3 amps or a bit more. If we say 3-4 amps, you should be looking at 6-8 amps total.
By any chance, did an earlier owner tie the TM's brake lights into the brake control line? That is unneeded and not planned for. An easy way to check is to pop the lens off the taillights (both sides) and remove the bulbs. Now what is the amp reading?
Do you have anything else tied into the brake circuit, like an electric tongue jack (hope not) or a front light, or ... ?
Rather than pulling the pin, what does your controller measure when you activate the brakes manually at the Tekonsha control?
If your rig is moving and you step on the brakes, what does the controller say?
Unless you have a DC-capable clamp meter, trying to measure the current at the brakes is a real pain because you must disconnect the wires. The wires are connected with wire nuts, which you must unscrew (easy) and then must re-apply - kind of a pain since you must make them waterproof. We discussed DC-capable clamp meters here on the forum, but even though they are cheap, I don't think many folks bought one.
https://www.trailmanorowners.com/for...light=clamp-on
As for your other question - why don't the brakes grab? - I think think the installation instructions say that you have to drive at relatively slow speed (30 mph?), then apply the brakes. (You can do this forward or backward.) Now do this 12 more times. ISTR that for me, I actually had to do this many more times before they first began to take hold. Take a look at the instructions again.
But resolve the brake line current issue first.
Bill