Troubleshooting Brake Controller With Low Voltage
Question:
I have the tekonsha p3 on a 2 axle four brake trailer and my unit is only putting out 3.5 volts. I tested it coming right out of the unit with a meter and have rechecked all connections. also only putting out .7 amps. what could be the problem. could the unit be bad?
asked by: Zach M
Expert Reply:
You will need to find out if the issue is on the brake controller, truck, or trailer. To test the brake controller, sever the blue wire a couple inches from the back of your controller. Then use a circuit tester such as # PTW2993 to test the end of the blue wire coming out of the controller. It should only have power when you apply the manual override; if it shows power at idle then there is an issue with the controller, and it will need to be replaced.
The next thing you will want to do is reconnect the blue wire and move on to the truck side trailer connector. Often, corrosion or dirt may be the cause of a short in a trailer connector. Check the plug to see if there is any type of corrosion built up that may be hampering its functionality.
You will also want to test the brake output pin; it should only show power with the manual override. If it shows power any other time then there is a short somewhere between the connector and the brake controller you will need to find.
If the truck side checks out, then it could be the wiring to the brake magnets or possibly the magnets themselves. Inspect the power wires to the magnets and look for wires that may be pinched or otherwise damaged and fix as necessary. You'll also need to make sure the ground wires are attached to bare metal surfaces, free of any paint, dirt or corrosion. Also be sure you are using a 30-amp circuit breaker such as # PK54530, which may be the issue if your input power is low.
You'll want to visually inspect the magnets; if you can see the copper windings coming through the magnets will need to be replaced. To test the magnets, you can follow the help article I have linked. I have also attached some help articles on testing and troubleshooting brake controllers for you to check out.
Products Referenced in This Question
Pollak Circuit Breaker - Cycling/Automatic Reset - 30 Amp - Straight Mount Bracket
- Accessories and Parts
- Wiring
- Circuit Breaker
- 30 Amp
- Pollak
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