Breakaway switch not working... and maybe brake issues

[Splash]

Regarding a 2001 TM 3023...

Problem: Pulling the breakaway plug out does not engage the brakes - the trailer still rolls fine.
... AND... I get an intermittent "trailer not connected" on my brake controller panel. Yet all interior and exterior lights work, AC plugged in works, DC works when AC not connected, appliances all work... all other electrical has worked since 2001. Except: until recently I never got the "trailer not connected" message.

I'll stop there for a moment - any suggestions just from that? Checked undercarriage wiring - nothing frayed etc., trailer battery is good - 13.2 V , and trailer brakes work when I use the truck brake controller. (except for a possible problem I'll mention below)

Continuing on... Pater C has a good picture of brake wiring:
https://www.trailmanorowners.com/for...0&d=1582075325(Sorry, tried to put inline but came out way too large. Is it OK to reference someone else's pic if I give them credit? if not, just say the word.)

Using that picture for my driver's side brakes, the 2 black wires are just pigtails, not connected to anything, not capped... nada. They are supposed to connect to the passenger brakes, right? And if they are not connected, have I only ever been engaging the driver side brakes? When I test the brakes, someone next to the driver side signals pass/fail and I never check the passenger side separately (believe me, that's not nearly the dumbest thing I've done with this trailer...oh the stories!).

However, the unconnected black wires problem seems like it would NOT be causing the breakaway problem... right? Maybe I've got 2 problems? 1) Pulled breakaway not engaging brakes AND 2) passenger brakes not connected.

I'll keep looking but please make suggestions if these issues ring a bell. Thanks in advance for any/all help.

And while I'm asking breakaway questions: Would checking voltage on the TM trailer electrical connector brake terminal be a reliable test to see if the emergency braking is working? My thought is that I should read 12V from brake terminal to ground when the breakaway is pulled and 0V if it's plugged in, but maybe there is something preventing flow into the TM connector? Any other electrical ways to check the breakaway working without actually driving forward and checking for brake movement? I only have a voltmeter with pins, not a clamping meter, and at what looks to be $100 minimum for a decent clamping meter, I'm just trying to get by without.

Anyway, thanks... hope you're all enjoying the 2020 summer.

[Shane826]

If you’re comfortable repairing wires, cut the 2 wires going to the beeakaway switch. If you have 12V & ground between those 2 wires, it’s likely a bad breakaway switch.

Let me think a little bit about the wiring and trailer disconnected message...

[Bill]

To see how to attach pictures to your posts, go to this article in the TM Technical Library here. It is easy.

https://www.trailmanorowners.com/for...ad.php?t=16117

Bill

[Bill]

Do you own (and know how to use) a DVM or VOM with an ohms scale?

Bill

[Larryjb]

When I first got my 2720, I had the same symptoms. It turned out in my case that the wires had been cut to the roadside wheel, and the magnet in the brake mechanism was badly worn and working intermittently. Bottom line is that it was a wiring issue. You should have a wiring diagram for the brakes to verify the wiring issue.

Because you are getting error messages at the brake controller, you have a wiring and/ or brake mechanism problem. I don't think there is any point in looking at the breakaway switch at this point.

[rickst29]

Originally Posted by Larryjb

Because you are getting error messages at the brake controller, you have a wiring and/ or brake mechanism problem. I don't think there is any point in looking at the breakaway switch at this point.

Exactly! The breakaway should provide full battery voltage (12v or higher) into the brake magnets, and the TV Brake Controller -> Bargman -> Brake Magnets should provide a variable voltage (between zero and full TV voltage), at each of the brakes.

There is an implication that the problem is at wire nut(s) where the two brake wires are interconnected with the switch output lead, or further down ("final" wiring closer to the brake magnets.) But trace everything, at every wire nut. If wire nuts are present they too many wires anyway - and deserve to be replaced with WAGO-Type clamping wire nuts. (individual spring-loaded clamps per wire, instead of HOPING that everything has remained twisted OK through years of vibration). IMO, using 'regular' wire twist nuts: 2 wires = excellent; 3 wires = only if they're all the same size; 4 wires = increasingly unreliable; 5 wires = never even dream of doing that.

[Bill]

Originally Posted by rickst29

... the TV Brake Controller -> Bargman -> Brake Magnets should provide a variable voltage (between zero and full TV voltage), at each of the brakes.

Beware of this thought. The brake controller will provide a variable AVERAGE voltage, as described and as desired. But the voltage is provided as a pulse train with constant-height pulses but variable-width pulses. Most inexpensive voltmeters actually measure peak voltage, because it is easy to measure. Some voltmeters, more expensive ones, measure average value or something similar called RMS voltage.

Bill

[rickst29]

Of course, that is how it works. But am I correct to assume that the 'pulse' waveforms occur hundreds or thousands of times per second?

I'm not sure if a $5 DVM will show al the peaking spikes separately from the average value, although an oscilloscope certainly would.

[Bill]

Yes, the pulses occur at a rate of a hundred or a few hundred pulses per second. You can hear the buzz or whine if you stand near the brakes while someone steps on the brake pedal.

The controller puts out a string of pulses. All the pulses have the same height (say 12 volts). And they occur at a constant rate (say 100 pulses per second), or one pulse every 10 milliseconds. What changes is the width of each pulse.

If all the pulses have 50% duty cycle (5 msec ON followed by 5 msec OFF), then the average value is 6 volts. If the controller makes all the pulses narrower (say 2.5 msec ON followed by 7.5 msec OFF), then the average value is 3 volts. And if it makes the pulses wider, then the average value is higher.

A meter that measures average value will tell you that the voltage in the first case is 6 volts, and in the second case is 3 volts. But a peak-reading voltmeter - and that is most of them, especially the cheaper ones - will tell you that the voltage is always 10 volts, because it reads the maximum height of whatever it sees, without regard to pulse width.

Aren't you glad you asked?

Bill

[rickst29]

Delighted, even. I had imagined the cycle time for a brake controller to be > 100 kHz, causing the meter to respond to the average (rather than the peaks). More like a solar controller in PWM mode.