So on our trip up here I experienced a strange problem. Normally when I apply my brakes my trailer brakes kick in via the controller. This time when I apply the brakes I'm only getting my truck brakes. I can still use the brake controller manually to slow down but it's worrying. Any idea what is going on.

 

What kind of controller? It may not be getting the brake signal from the stoplight switch, could be fuse or relay... Number of things.

 

Tekonsha Primus P2

 

Check the red wire going into controller for power when brake is applied. If it is getting 12v then I'd bet the controller is toast.

If it isn't, confirm that your brake lights work, if they don't check for blown fuses (assuming you haven't) or a bad stop lamp switch.

I am almost certain there isn't a separate fuse powering the brake feed from the stoplight switch, but I could be wrong.

 

Try the frame ground at the rear of the vehicle. Recently had this exact problem and that fixed it.

 

I had my P3 controller go bad. They replaced it free. After it went bad again I realized it is probably my fault. When I hook up the trailer I was pulling the break-away to thread it through the bumper. Having the main trailer plug plugged-in before I did that may have been the cause of the controller failure. Added a clip to the break-away so I don't have to pop it to hook it up and it has been solid since.
Even if that's not the cause, Tekonsha has good customer service so might be worth a call. I'd do a fuse check first.

 

I realized I should update this thread now that I'm home and figured out what the problem was. I'm quite embarrassed...

I wasn't even aware of the 'boost' button on my brake controller (this is my 3rd year towing....). I must have hit it at one point because it was completely turned off. Once I figured out that button and properly adjusted I got my trailer brakes back.

 

To add to this,

The boost feature even when off doesn't turn off the brakes.

In non boost mode or standard mode the controller needs two things to happen before sending output power.

1) signal from stoplight switch
2) inertia sensed from deceleration

With those two things the controller quickly determines how much of a percentage of the number you have it set at, to send to the brakes.

If you come to a slow gradual stop the percentage will be low, if put the pedal to the floor it will be close or at 100%.

At this point as you slow down the controller will back off as your deceleration lightens.

NOW, with boost level 1,2, or 3 engaged.

As soon as the controller senses the brake lights are on it will send a small percentage (10% ish on level 1, roughly 20% on 2, and 25 or so % on level) before it even calculates the deceleration.

Once it does calculate that it will go higher as necessary.

If you barely touch the pedal but don't actually engage the vehicle brakes you will feel the brakes coming on. I do this when I'm towing if I see brake lights cone on ahead. It basically is a function of getting the power to the brakes quicker - not necessarily more power or higher power.

Lastly, if you hold your foot on the brake for about 5 seconds while at a stop, even with the boost off, the controller will send about 25% of the setting it is set at to give "holding power" in an instance of being completely stopped on a hill at a stop light.

I run the boost off on my trailers while in town but on the heavier loads I go to boost three when I'm out doing 50 and up mph.


Hopefully this sheds a little light on these suckers.

Joe