Kelsey Hayes 6Volt -12Volt electric/hydraulic brake controller

Now and again questions come up about these old units.
Will they stop a trailer, are they any good?

The answers are yes.
Another question is where to buy one?
They stopped making them some years ago, but E bay is a good source.
Mostly used controllers are offered, but sometimes NOS (new old stock) units are up for bids.

Although they are "automatic", they don't have fancy electronics like today's brake controllers.
They are automatic by mechanical means.

When you apply pressure to your brake pedal, the fluid in the brake lines push/put pressure on the brake lever on the controller, allowing the electrical contacts to meet.

The more pressure put on the electrical contact spring, the more electricity is sent to the trailer brakes.
The more electricity that is sent to the trailer brakes, the more the brakes are applied.

The hydraulic brake function ends completely at the brake controller, no hydraulic brake lines or fluid go to the trailer.
Only electric current runs from the controller, to the trailer brakes.

The pressure applied by the brake pedal applies pressure to the lever on the controller.
The harder you push the brake pedal, the more electricity is sent to the trailer brakes.

As with modern controllers, there is a bypass system that allows you to manually apply the trailer brakes without applying the cars brakes, and a "sensitivity" control.

On the KH. controller, it is the arm that projects from the controller.
The further you pull down, the more power is sent to the trailer brakes.
The arm also screws in, and out, of the controller body.
This action adjusts how quickly the electrical contacts meet.
Some people like to adjust them so the contacts don't begin to connect until the arm is pulled half way down.
Others like to set it so full contact is made very quickly (less travel of the arm).
The best adjustment allows the trailer brakes to just begin to be energized before the cars brakes make contact.

You may have noted that the title implied 6, or 12 Volts.

The unit is very capable of, and designed to operate on a power supply of 6, or 12 Volts.
Slightly different wiring connections are made, depending on the size of the power source.

Connecting one of these units is fairly simple...if you have an old car , and don't mind cutting into the cars brake line.
No big deal on an old car (old to me is 1960's and earlier) but not something I'm going to suggest on something newer that may have electronic systems...

It works very well for me, then again, I am NOT an automotive technician, nor am I qualified to offer advice on brakes.
I would guess that if you are an expert in your field, and know all you need to know about brake systems, you probably aren't reading this anyway...

So, if you are considering installing one of these units, please make sure you educate yourself, and or seek advice from a qualified person.
Electric trailer brakes, and electric trailer brake controllers are VERY simple devices.

I own a couple of these units, and currently have one connected on an old car.
The car is actually much older than the "vintage" controller, and doesn't have any "brake lines".
It has mechanical brakes, that is, a system of rods and levers transfers the pressure I put on the brake pedal to the brakes.
Works great, no brake fluid or leaks!

As designed, like most cars, they do a great job of stopping...the car.
But add a trailer, and it just isn't enough!

Since I didn't have hydraulic brakes, I simply removed the hydraulic portion of the controller.
It is just a matter of unscrewing the fitting, and removing the hydraulic piston.

Now the controller is no longer "automatic", but fully manual.
If I want the trailer brakes to work, I must manually pull down on the lever.
Though not for everyone, pulling the lever to stop a trailer while driving a 1928 Ford works very well for me.
The trailer brakes are very powerful, and I actually don't even bother to apply the car brakes, the trailer brakes alone are enough to stop both!

The wiring is very easy.
There are just three wires coming out of the controller.

The black wire is connected to power, battery or otherwise.

The blue wire is connected to the trailer brakes.

The Red wire is connected to the stop light circuit.

When the trailer brakes are applied, either by means of the automatic feature, or manually, an electrical connection is made between two contact points that sends power to the stop light circuit, which lights up the brake lights.

Here are some photos of an NOS unit.


The silver tube with the brass connection on top is the hydraulic cylinder and connection point.


In this photo, you can see the bottom of the hydraulic cylinder which pushes against the controller arm.
Grab the lever and pull down, or push the brake pedal and the hydraulic pressure pushes the contoller arm down.

In this photo, I have inserted an empty bullet cartridge under the hydraulic piston to show you what happens when you apply pressure to the brake pedal, or pull down on the arm.
Note the position of the coil spring, and the flat spring.
The red piece in the middle is what moves when the lever is screwed in, or out.


And this is what came originally in the package when you bought a brand new Kelsey Hayes brake controller.
It also came with instructions, please see below.





Hope you found this useful!


Edited 4 times by 48 Rob Mar 18 09 6:55 PM.