Brakes

I tried the compass test last month and it didn't work (brakes work).

Didja ever get the brakes (stinking) overheated ? That can put a hard glaze on the lining that is so hard you can't hardly file it,...deciphered as, very little stopping power.
Or, very cheap hard lining can cause the same thing

......I have very little brake pressure when I step on the brakes



That sounds like TOW Vehicle brake issue vs trailer brakes.

I can't tell any difference in trucks brake pedal action whether towing or not seeing as how Trailer Brake Controller is ELECTRIC Signal vs a hydraulic

Now if you mean.........
Very little trailer brake 'action' then trailer brakes need:
adjusted
wire connections checked
magnets tested
and/or brake assemblies visually inspected.

Quick magnet test
Hold a compass down low next to drum
Have someone pull Emergency Breakaway Pin
Does compass needle deflect towards drum??
YES...adjust brakes
NO...check wiring/magnets

Did they replace the seals? Maybe grease has gotten onto the brakes? We had failed seals on a previous TT from brand new. The brakes would grab and shudder all the time and even lock up on gravel with just a little pedal pressure. A year later, the dealer finally agreed to inspect the brakes and found blown seals and totally rebuilt everything under warranty. Dealer kept insisting all along that it was our brake controller.

Have someone apply the P3 manually while you measure for about 3 amps at each wheel with your clamp-on ammeter.

Of course if this started after the shop worked on it you could take it back or to someone new.

If mine has been sitting for a bit it does take 4 to 10 stops before the brakes get back to normal. You should always feel a strong pull if manually applied.

Did the "they" who checked them test for voltage at the magnets, and if low or no voltage, look for and fix the problem such as loose or broken wires? If not, you should put them back on the job, if they're qualified, because I think they done you wrong. If everything on the TT checks out, then it's on the TV side, perhaps with your controller or wiring.

Manually adjust them? You should be able to spin the wheel and it should have just a slight amount of brake drag on it.. Yes, you should hear the brake scrapping on the drum and that's when they are adjusted properly.

If you can spin the wheel and you don't hear anything, they are too loose.

Good luck!

Mitch

How are the magnets?