Brake Controller Troubleshooting

[Kevin A]

After a recent communication to Tekonsha, they said my intermittent P3 controller issues are probably high resistance in the wiring somewhere, possibly corrosion. As an electrical newbie, how do I check for high resistance? Also, do I need to check all electrical connectors to each wheel and any ground connections? How about the 7 pin plug and socket? Basic help is appreciated!

[Defenestrator]

To check for high resistance, you need a multimeter.

You'll want to learn a little about DC power. Specifically how current, voltage, and resistance interact.

Actually measuring resistance can be done directly or indirectly. That is, you can either disconnect the wire from the power source and just measure the resistance on the multimeter, or you can can put the multimeter in voltage mode and measure voltage on the wire when power is flowing through it vs when no power is flowing through it. If you know voltage drop and current, you can get the resistance on the wire then compare that to what it should be based on the length and diameter/gauge of the wire.

A visual inspection may also be useful. Especially check the connections on either end of the wires for corrosion or loose connections, but also trace as much of the wire in-between as you can looking for compromised insulation that might have let water in.

[Iowa Dave]

From past experience early in the spring, the first place I would check for corrosion is the seven pin on the tow rig and then the plug on the camper. Winter salt spray is an enemy and often shows up in the spring, The pins need to be clean too. Next I would check the Hot leads coming off of the tow battery. Finally from there, the pigtail on the back of the brake drums where it attaches to the trailer loom. Don"t know about a Bigfoot but on the Escape there's a split plastic cover over the brake pigtail and connection. Corrosion can occur here too. Those are the easy starting points for me. Hope this helps.
Iowa Dave

[steve dunham]

If you try contact cleaner to clean up the connection points be cautious
Some of the contact cleaners on the market are nothing more than glorified alcohol and don’t do a good job of removing oxidation/ corrosion.
Others are not plastic safe and you can turn bad into worse .
The problem is they have banned the good stuff , that actually worked so now you have to use 10 times the amount of the new and improved stuff
Also be cautious with cleaning the contacts with a file , you can remove the conductive plating and destroy the contact . A fine emery board works well, aluminum oxide sand paper does not

[Kevin A]

Thanks everyone. When I get the trailer back from storage, I'll start the examination process!

[Byron Kinnaman]

Originally Posted by Kevin A

After a recent communication to Tekonsha, they said my intermittent P3 controller issues are probably high resistance in the wiring somewhere, possibly corrosion. As an electrical newbie, how do I check for high resistance? Also, do I need to check all electrical connectors to each wheel and any ground connections? How about the 7 pin plug and socket? Basic help is appreciated!

For you the best bet may be to take the trailer to "TRAILER" shop and have them check it all out for you. They have more experience than anybody has with trailers.

[Glenn Baglo]

Paying a shop $70 to $90 an hour to track down an electrical problem that isn't obvious is a sure fire way to go broke.
I had an issue with the left turn signal. Hitch shop removed the 7pin housing and a bunch of other stuff and replaced it. Cost for parts, but shop hour was $70 and when they were done, it worked.

[floyd]

Start by plugging it in to a known good trailer. that would eliminate half the problem.

Try and plug your trailer into a known good TV.
This would tell you which vehicle is at fault and give you a place to start. You could borrow a known good P3 and plug it in to your rig as another test.
After this, get out your VOM.

[Captleemo]

It doesn't hurt to spray some WD-40 on the connections before you plug them in.

[Byron Kinnaman]

Originally Posted by Glenn Baglo

Paying a shop $70 to $90 an hour to track down an electrical problem that isn't obvious is a sure fire way to go broke.
I had an issue with the left turn signal. Hitch shop removed the 7pin housing and a bunch of other stuff and replaced it. Cost for parts, but shop hour was $70 and when they were done, it worked.

Sometimes paying for repairs is cheaper than the alternative. If you try and fail the results can be as much as the loss of the trailer, not too likely but possible. A couple hundred dollars is cheap compared to the cost of the trailer. Also if you do the work your self there's no recourse. If somebody else does the work you go back on them for restitution.

There are lots of reasons to have a shop that has insurance do the work other than initial costs.

[steve dunham]

Originally Posted by Byron Kinnaman

Sometimes paying for repairs is cheaper than the alternative. If you try and fail the results can be as much as the loss of the trailer, not too likely but possible. A couple hundred dollars is cheap compared to the cost of the trailer. Also if you do the work your self there's no recourse. If somebody else does the work you go back on them for restitution.

There are lots of reasons to have a shop that has insurance do the work other than initial costs.

i did electrical service calls / troubleshooting for 40 years
i would walk onto the jobsite and before I opened my tool box and examined the problem the customer would ask me what I thought was causing the problem , how long would the repairs take , what the repairs would cost ,insinuate that I was trying to run up the bill and then tell me how to fix the problem . On several occasions I picked up my tools and left
My experience told me that the customer was going to contest the bill and then refuse to pay . If you follow some people’s logic you would never go to a doctor cause the bill might be too high !

[redbarron55]

If you want to trouble shoot the brakes yourself the most important thing to do (as with and process) is use a logical step by step approach.
First thing to do is to get a good ohmmeter and check:
1. Resistance from the brake pin to ground on the trailer Pin #2. Each brake coil should measure 4 ohms to ground or 2 ohms total since they are in parallel.
A. If the measurement is not 2 ohms (measured to a clean spot on the trailer frame to get a good ground) then then is it 4 ohms indicating one coil not in the circuit or higher indicating a bad circuit.
B. The most likely bad spot is where the trailer coil is grounded to the frame and where the splice (read crimp connector) connect to the brake wiring to the plug.
2.If you have a meter that reads DC amps then the brakes should draw about 3 amps (each) with 12 volts across them.(read that a total of ~6.3 amps) together.
B. If you checked at the resistance at the trailer plug then you should know if your problem is on the trailer side or the TV side now.

There are several points where you could have a bad connection.

1. At the brake coil wires one to ground one to the trailer brake wiring (two sides 4 connections.
2. Where the two brakes tie together to go the the front plug
3. Where the plug pigtail ties into the other part of the trailer wiring.
Since the brake coil wires are under the trailer and exposed to the weather, rain and road hazards this is a likely spot to find the problem.

Step by step wins the day.

The technician will have to do these same things as you, but the cost will be $40 - 70 an hour.

15 minutes of time his time will buy you a good enough meter at Harbor Freight

A common problem is often a poor connection through the #1 ground pin and there might not even be wiring on either side with the hookup relying on the ground through the ball and hitch (a bad idea).
Check pin #1 on both sides first as this is a very likely trouble point if there is no good connection to the frames on one or the other sides.

Often corrosion at the grounding screws and the crimp terminals cause troubles like this

[Terry J]

I had intermittent brake controller problems which were fixed by replacing my trailer brake magnets. The etrailer website has troubleshooting suggestions -- https://www.etrailer.com/question-86077.html

[computerspook]

I would start by finding some deoxit.

https://www.amazon.com/Hosa-D5S-6-De...03658380&psc=1

Spray this on both connectors and plug and unplug them several times. See if that makes the problem go away. I use this as a normal service practice and the start and end of the season.

[Raspy]

A common "high resistance" problem is a poor or non-existant ground connection. A large group of Olivers had this problem where the ground connection was not made to the frame and the trailers would not charge from the TV. It also triggered a warning in Ford TVs.

When this is the case, the trailer grounds through the trailer ball, which is a very poor connection and leads to brake problems and charging problems. But there is enough of a connection that some things will work.

I found mine by tracing the ground wire in the 7 pin pigtail to where it connects inside and discovered there was a missing jumper wire. The brakes worked, but the batteries would not charge from the TV.

A quick test is to see if the battery voltage rises consistently when plugged in and the TV running. Do this with the trailer plugged in, but the hitch coupler disconnected. Your battery voltage should immediately go up over 12.5 and reach about 14 if given some time. This means it's charging. You can also connect a jumper cable (conventional battery jumper cables) from a good ground point on the trailer frame to a good ground point on the TV and see if that cures the problem. You can do this while parked and you can drive around with the jumper cable connected to see if the controller works as it should while braking. Then make the necessary ground wire repair if needed.

If none of that fixes the brake controller problem, it's probably in the controller output current wire that runs the brakes.

The 7 pin plugs can get corroded, damaged or just dirty too. A good rinsing with WD40 and a visual check of the pins will help eliminate this as the problem. I had one that was very hard to plug in and it was easy to not get it all the way in, which meant it was partially disconnected. Be vary careful and deliberate with the plug to make sure it is engaging properly and going all the way in.