Brake Controllers (excessively long)
There are four basic types of trailer brake controllers available.
1. Electric-Electric Ramp type - This is the simplest and least expensive and each of the manufacturers makes one. I used one for one year. The controller takes it's input signal from a wire in the tow vehicle leading from brake light switch to brake lights. Although simple, the driver cannot modulate trailer braking with this type. When the brakes lights are energized, the controller is turned on and braking force begins increasing slowly. On a graph, braking signal to the trailer would be seen as a ramp increasing over time. This type works pretty well when towing a trailer that is lighter than the towing vehicle. The problem is, if you call for slow, gentle braking, the trailer brakes will ramp up (increase) as the driver's foot remains on the brake pedal until trailer braking exceeds the driver's intentions. The driver can compensate by lifting his foot from the brake pedal and reapplying, thereby restarting the ramp.
2. Electric-electric Inertia type - Tekonsha is a major manufacturer of this type. I have used this type, two of them actually, because Tekonsha gave me a free replacement. If you tow a relatively light trailer behind a heavy Dodge-Cummins you may like it. The controller attempts to modulate trailer braking with a pendulum inside the controller that swings as braking force is appllied. One of the major problems with this controller is if the trailer is very heavy, the tow vehicle has difficulty creating deceleration to start the controller. It can NEVER be permanently adjusted but requires constant tweaking all day, every day you pull. If you set the gain for light braking then have to make a rapid stop, you will have inadequate trailer brakes. If you set the gain for hard braking then make a gentle stop, you will endure jerking, bucking, even trailer brake locking. If you are braking when you cross a pot hole or railroad track, you will get jerked around by your trailer brakes. If you brake on a downhill grade, you will have excess braking. If you brake on an upgrade, you will have little or no trailer braking. Thousands of them in use but, in my opinion, not a very desirable product.
3. Hydraulic-Electric type - Years ago, before ABS brakes, everyone used a Kelsey-Hayes controller. You installed it by cutting a brake line downstream of the master cylinder, installing a tee, then routing a hydraulic brake line through the firewall to the controller. Once installed and adjusted, it provided perfect, measured, controlled braking that precisely matched the driver's request (foot pressure on the brake pedal. ) Lawyers, lawsuits, and careful auto manufacturers and trailer dealers killed the product and it is no longer manufactured although lots of them are still around. Regardless of everything the RV industry tells you, they can be used on late model trucks with ABS brakes. Chevrolet/GMC truck brochures acknowledge that they can be used if the controller displaces less than 0. 02 cubic centimeters of brake fluid. They displace less than 0. 01 according to Hayes-Lemmerz, the current company name. I used one for years back in the 70s and used a new-old Kelsey-Hayes hydraulic-electric brake controller successfully on a 94 Ford F250HD to tow a heavy Airstream. When I retired the Ford recently I kept the controller but have not yet installed it in my Dodge. I had trouble finding a suitable tee fitting for the Dodge so installed a new Hayes inertia type controller (which is a far better product than the Tekonsaha). In truth, I am a little timid about installing the old K-H controller because of the electronic brake proportioning circuit although I persuaded a Dodge help line spokesman to admit that it was not inherently unsafe to use a hydraulic-electric controller on a new Dodge. Actually, the Hayes inertia operated controller works well without the constant tweaking required by a Tekonsha so I am not in a hurry, but the inertia controller is not a substitute for the old fashioned hydraulic-electric controller.
4. Mechanical-Electrical type - The Jordan Ultima is of this design. A cable is attached between the tow vehicle's brake pedal or brake arm to the controller. When the driver depresses the brake pedal, the brake controller is actuated proportionally. The Jordan provides brake modulation similar to the old style K-H hydraulic-electric controller without tapping into your truck's hydraulic brake lines. I have not used one but everyone who has says they work very well. The only drawbacks I am aware of are the need to install a mechanical cable between truck brake pedal and controller and, as brake pads/brake shoes wear, braking will require slightly more brake pedal travel to get the same level of braking, which may increase trailer braking. This drawback could, I'm sure, be compensated for by adjusting the brake controller's gain setting.
I hope this too long discussion helps someone.