If you want to trouble shoot the brakes
yourself the most important thing to do (as with and process) is use a logical step by step approach.
First thing to do is to get a good ohmmeter and check:
1. Resistance from the brake pin to ground on the trailer Pin #2. Each brake coil should measure 4 ohms to ground or 2 ohms total since they are in parallel.
A. If the measurement is not 2 ohms (measured to a clean spot on the trailer frame to get a good ground) then then is it 4 ohms indicating one coil not in the circuit or higher indicating a bad circuit.
B. The most likely bad spot is where the trailer coil is grounded to the frame and where the splice (read crimp connector) connect to the brake wiring to the plug.
2.If you have a meter that reads DC amps then the brakes
should draw about 3 amps (each) with 12 volts across them.(read that a total of ~6.3 amps) together.
B. If you checked at the resistance at the trailer plug then you should know if your problem is on the trailer side or the TV side now.
There are several points where you could have a bad connection.
1. At the brake coil wires one to ground one to the trailer brake wiring (two sides 4 connections.
2. Where the two brakes
tie together to go the the front plug
3. Where the plug pigtail ties into the other part of the trailer wiring.
Since the brake coil wires are under the trailer and exposed to the weather, rain and road hazards this is a likely spot to find the problem.
Step by step wins the day.
The technician will have to do these same things as you, but the cost will be $40 - 70 an hour.
15 minutes of time his time will buy you a good enough meter at Harbor Freight
A common problem is often a poor connection through the #1 ground pin and there might not even be wiring on either side with the hookup relying on the ground through the ball and hitch (a bad idea).
Check pin #1 on both sides first as this is a very likely trouble point if there is no good connection to the frames on one or the other sides.
Often corrosion at the grounding screws and the crimp terminals cause troubles like this