7 PIN INSTALLED WITH 12 GAUGE AND 20AMP FUSE

The hot 20amp wire on the 7-pin is used to activate the brakes in the trailer and charge the trailer battery.  Perhaps between the two, the 20-amp fuse is blowing, I do not think,this has anything to do with the brake controller, which draws less than 1 amp itself, and just passes the connection to the brakes, hence the 30-amp requirement to do both.  On a hard brake, at 20-amp, it is getting maxed out.
cheers

Ah, thanks. That makes more sense.

The Autowbrake controller i just added to our 320 *also* pulses the brakes when the hazards are on. I was so disappointed. Are there any brake controllers that behave correctly without needed to be wired to the brake pedal switch?

Yes, a factory type brake controller designed for the specific TV is the best solution.
that said, it is illegal to drive with hazard lights on while moving, this is the rule in Calif., but a lot of folks do it.  Flashing lights around here are for emergency vehicles only.
cheers

Good point.  But these trucks are going very slow, under 20 mph, so is a valid use, as is stopped in a traffic lane or shoulder.  I use mine when almost stopped on 2-lane Hwy 1 when some one is stopped trying to turn left.  But having a brake controller pulse your brakes is an issue, if you are trying to go slow, like up a steep grade.  
Cheers

For calculating electric brake draw, one needs to start at the magnets or "pucks". There is one magnet inside each wheel hub, so a single axle trailer has two.  For standard 7" or 10" brakes (T@B, T@G etc) the MAX amperage draw per magnet is in the neighborhood of 3-3.5 amps.  So the total draw during hard braking is around 7 amps max. You need to factor in around 3-5% loss for wire length. Just figure 1/2 an amp for that. This brings the total amperage load to less than 8 amps. For normal braking, not neck-jerking stops, you'll probably have your controller set to 50% or less.
If you are roasting your wiring and blowing a 30 amp fuse, you've got bigger problems. Here's a wire sizing chart:
http://fettingpower.com/home/helpful-references/wire-sizing-chart/

You can figure that a circuit should be sized at the capacity of the fuse, or the maximum amperage potential of the fuse. For a twenty amp fuse more than 10 feet long, you will need a 10 gauge wire.  Not difficult to calculate.

Let's assume that ALL electrical connections are good. (This is not the case with my T@G. I ended up replacing several splices within the wiring due to failures.) Remember that in a 7 way circuit, there are more than brake amperage requirements. If you add up the individual potential amperage in ALL of the circuits, you'll find it's a surprisingly high number.  All of that current potential feeds to the trailer on separate circuits, BUT! It all returns to the tow vehicle on ONE wire! The ground wire in the 7 way connector must be capable of handling the combined amperage of all 7 circuit potentials.  Thankfully, this rarely happens and when it does, it's usually for no more than a few seconds at a time.  You've got a 12 gauge (too small) wire going to the brakes, a 10 gauge charging wire, 16 gauge wire for various light circuits.....and one...single 14 gauge wire for the trailer ground. That is going to be one hot, busy wire. Do yourselves a favor:
First order of business in trailer wiring should be to make sure the ground wire coming from the trailer, through the 7 way receptacle, then back to the tv battery (not duct-taped to the exhaust tip for a ground) is 10 gauge, has proper butt connectors,( crimp-on connectors are fine so long as they are either heat-shrinked or are the heat-shrink type. These can be had at any auto parts store. They have a heat sealer within the connector so when you heat shrink them, the sealer melts and completely coats the inside of the crimp. Expect to pay $6 bucks or more for 5 or 6 connectors. If you are bound and determined that you don't need to run the trailer ground back to the tv battery, then at least use a nickel plated ring connector that won't rust, then seal it with some sort of coating to keep the water out.
99% of ALL light, brake, charging circuit problems on trailers can be eliminated by paying attention to the ground wire that goes from the plug to the chassis/battery on the vehicle side. If you go out and look at the ground wire on your vehicle-side trailer wiring, you'll see that it's no larger than the turn signal wire.  I've seen factory and aftermarket wiring harness plugs that are as small as 16 gauge.  NuCamp runs 10 gauge ground wire through the trailer connector to the plug. Do the same on the other side of it and you'll eliminate 90% of your problems. You might (will) also find that your tow vehicle can now charge your trailer battery in 1/3 of the time.

WilliamA