Is my Tekonsha Prodiby IQ brake controller bad?

[MartyW]

Hi All,

We just got a different TT (5 yrs old) and I'm checking and tweaking to make sure all is road worthy. Our brake controller is a two year old Tekonsha Prodigy IQ. All lights and functions of the controller appear to be normal except operation by the brake pedal. The boost button and manual control lever both seem fine.

I've checked blue wire voltage from brake controller through trailer connector and through the junction box under the trailer all the way to the wheel backing plates and the signal is good and strong all the way.

As the manual control lever is applied, blue wire voltage smoothly follows the controller display as the display goes from 0.0 to max 12.0.

The strange part (to me) is that when the brake pedal is depressed the controller display shows an increase from 0.0 to only about 2.4 and then as the brake pedal is depressed further the controller display drops back to about 1.1 until the pedal reaches nearly full travel down and then sometimes (not always) the controller display quickly goes to somewhere between 4 - 6. But it will never reach its max setting by using the brake pedal. This is with engine running.

The way I found this issue was that I had my wife pressing the brake pedal as I was checking blue wire voltage at the different points, and this is exactly what I saw happening in the voltage test light. That is, the test light would start out completely dark as it should with no voltage, then as the brake pedal was being depressed the voltage would increase to a "dim" light on the tester, then the tester light would go almost completely out and then sometimes as the brake pedal reached full travel (as far as it will go with TV stopped in park) the test light would sometimes go bright. That action of the test light is what caused me begin to check the controller panel itself, and the controller display seems to show exactly what I see in the test light when using the brake pedal. But, with the manual lever, the signal is smooth and full. Sorry for the long post.

Thanks in advance

Edit: Forgot to mention that all connections and mountings seem tight on the brake switch.

[RCMAN46]

Here is a quote from the instruction manual for the Primus IQ controller.


The Brake Control will HOLD your trailer with
25% of power setting while you are at a standstill
with brake pedal applied for longer than 5 seconds.


b.I , during a braking event, the power automatically
starts out at approximately 13% of the power setting and
increases with deceleration. With the boost on level 2,
b.2 , or with the boost on level 3, b.3 , during
a braking event, the power automatically starts out at
approximately 25% of the power setting and increases
with deceleration.

[MartyW]

Maybe that's why it seems strange to me, this is the first proportional controller I've ever checked/traced.

Thanks Scott and Todd. That is what I needed to know. I will proceed to the road tests now for the tweaking.

Thanks again.

[MartyW]

It is a proportional controller according to the specs. Thanks

[Toddupton]

Isn't that a proportional break controller? So the break voltage is based on deceleration. If you are doing 10 miles an hour you get less breaking than stopping from 60 mph.

[ScottG]

It needs some inertia (as measured by an accelerometer) to apply full power to the brakes. As it just sits there, there is no need for full braking force.
Also, pushing your pedal harder does not apply more trailer brakes. It's the sudden slowing down and the brake light on that triggers the controller to apply more brakes.
So the good news is your controller is working properly.