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Old 04-18-2021, 03:56 PM   #1
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2021 27' Globetrotter
Rochester , New York
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Sporadic Trailer Brakes

Hoping to tap into the collective wisdom here. We are two days into our first long trip with our new GT and the trailer brakes are making us extremely anxious.

We did a short shakedown trip last week and during the trip I lightly (and then fully) squeezed the brake controller, and nothing happened. No braking (gain was on 6). We were close to our campground and when we arrived I was able to fix it by reducing the gap in the blades in the 7-way connector. The trailer brakes worked fine after that.

This happened again yesterday. I again pried the blades closer together and the brakes were working when we left our campground but then part way through our drive today they again stopped working. I tried prying the blades together again but it initially didnít work. Eventually, after about the 10th time I connected the 7-way to the truck, the brakes started working and were good for the rest of our drive.

My guess is that the 7-way isnít engaging properly. But I also put a multimeter between the ground and brake pins on the 7-way and never got anywhere near 12V when the brakes were tapped and on a gain setting of 10.

Any thoughts on a likely cause/solution would be greatly appreciated as weíre trying to decide if we should just play this day-to-day or interrupt the trip to get this fixed.

Thanks
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Old 04-18-2021, 05:16 PM   #2
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2018 27' Globetrotter
Mooresville , North Carolina
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I don't know if this is your issue or not. I was looking under my Globetrotter one day and saw a loose wire hanging down behind one of my wheels after a trip. Basically, when assembled they were leaving a big loop in the brake wires hanging underneath. Any piece of a road hazard probably flew up and broke it.

The other issue is that they connect a thick wire to a thinner wire with just a butt connector and that is prone to just breaking with the movement of the wire bouncing. This post describes issue and resolution starting at post #2. It helped me fix my problem.

https://www.airforums.com/forums/f43...es-200944.html

I know you are thinking it is the 7 pin connector but it may be something else. it may be you have a partially connected wire that makes contact / then it doesn't / then it does / then it finally breaks.
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Old 04-18-2021, 08:37 PM   #3
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Years ago I had a similar problem--first brakes, then no brakes. Turned out the trailer ground connection under the "A" frame was corroded. I had an intermittent ground thru the hitch assembly. A new lug on the ground wire with a new bolt tapped in with a grade 8 star washer fixed my problem.

This was on a 1973. The trailer light wiring may be different on yours. So locate where your tow vehicle wiring grounds to the trailer chassis. Probably this will be in the front of your trailer and your owner's manual may tell you where to look.

You can do a crude test by running a wire from the positive terminal of the tow vehicle battery that normally powers the trailer wiring. Check the voltage from this wire to the trailer frame. If you have a good trailer ground you should see essentially the same voltage from the wire to the trailer chassis as you do across the battery's terminals. If the voltage is lower or varies, then your ground connection is suspect. Be aware that an intermittent ground is, well, intermittent, so this test can give you a false result. Disconnecting the trailer from the tow vehicle so the only electrical connection is thru the 7 way umbilical should help.

Poor grounds can cause some interesting symptoms. Have you noticed your running lights dimming and brightening? Have you noticed your running lights blinking or going out when you use a turn signal or step on the brakes?

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Old 04-18-2021, 08:54 PM   #4
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When that happened to us, we found that the connections had already corroded - even on the brand new unit just delivered on the lot. So, we always have one of my wife's emery boards narrowed to fit inside the double prongs ... very light sanding is required for us about every 4 or 5 trip ...YMMV
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Old 04-19-2021, 04:55 AM   #5
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Tow vehicle info make, model, year and does it have integrated brake controller?

You measured voltage, not near 12V right? What was the actual measured voltage?

7 way receptacle is the hinge for the cover on top, side or bottom? Yes it can impact the plug connection.

Gary
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Old 04-19-2021, 05:12 AM   #6
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2021 27' Globetrotter
Rochester , New York
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Thanks for the replies. I will check the wiring/ground best I can today.

TV is a '21 F-150 with integrated OEM brake controller.

Measured V inside the truck connector was less than a volt though I want to recheck this. Any idea what this voltage should vary between?

Hinge cover is on the top side. But when fully inserted the plug never feels super secure.

If there is corrosion inside, would a small shot of di-electric grease or contact cleaner be a possible fix?
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Old 04-19-2021, 06:39 AM   #7
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Is the 7 pin plugged all the way in? I have to bump mine with a hammer to fully seat it. It goes in 1/8 inch further than I can seat it by hand. You need to fix the faulty connection. New plugs on trailer and truck maybe. Once that connection is solid you can troubleshoot further.
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Old 04-19-2021, 07:15 AM   #8
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I had a similar problem with my F150, in fact its something you can google on the F150 forums. Also I don't think its possible to check voltage at the 7-pin connector without the trailer plugged in. The truck computer needs to detect the trailer prior to powering that plug.

Because you're pinching the blades inside the trailer umbilical causes things to work for awhile leads me to believe that's the source of the trouble. It waa for me as I did exactly that for awhile. Are the blades recessed about a 1/8" or more inside the trailer plug? The Ford 7-pin plug wants a tighter fit.

My solution which had been permanent was to replace the Airstream umbilical with another where the electrical blades are flush with the face of the trailer plug.
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Old 04-19-2021, 02:20 PM   #9
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I wish I had a fact based measurement of IF an ITBC (integrated truck brake controller) software turns off the brake signal output if the vehicle is not in motion or in PARK. I did try to measure it on a newer Ford ITBC and didn't get a signal. Also not sure if the new ITBC uses pulse width modulation as a signal. It's just more food for thought.

A while back I did a review of several 7 Way plugs and how they connect to the receptacle. This is that thread with a few pics.

https://www.airforums.com/forums/f23...ighlight=7+way

I have measured live trailer brake controller voltage of a stopped vehicle a Tacoma and output was 10.1VDC and about 13 amps. Yes, both measured. I made my own inline brake circuit voltage and amperage tester.

To measure the intact circuit see if you have a black box at the front of the trailer and remove the cover, two screws. It's about 6X3X2 inches and has (at least on mine) 5 of the 7 wires. The charge line and ground connected directly not in the junction box.

Now look for a BLUE wire. Ground meter on white 12V ground bar and put meter + on blue terminal. Have someone run the slider. See what you get.

The top hinged receptacle hooks onto the plug and does a real good job of hooking and holding the plug. Bottom hinged doesn't and side hinged can't make up it's mind. Look at the pics in my 7 way and insertion marks.

Gary
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Old 04-19-2021, 07:31 PM   #10
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Quote:
Originally Posted by kscherzi View Post
I had a similar problem with my F150, in fact its something you can google on the F150 forums. Also I don't think its possible to check voltage at the 7-pin connector without the trailer plugged in. The truck computer needs to detect the trailer prior to powering that plug.

Because you're pinching the blades inside the trailer umbilical causes things to work for awhile leads me to believe that's the source of the trouble. It waa for me as I did exactly that for awhile. Are the blades recessed about a 1/8" or more inside the trailer plug? The Ford 7-pin plug wants a tighter fit.

My solution which had been permanent was to replace the Airstream umbilical with another where the electrical blades are flush with the face of the trailer plug.
Yes, blades are recessed about 1/8". Earlier today I stopped at an RV shop and picked up a new 7-way trailer-side plug (pins are flush). My plan was to swap out just the plug but the stock AS plug looks to be molded to the umbilical and not removable from it. I thought about just cutting off the stock plug and wiring up the new one but I'm concerned about ending up with too short a cable to reach the truck. I have a ProPride hitch which adds a foot or so of distance over a standard hitch.

In the morning I'll try to seat the connector as tight as possible and the get the trailer somewhere that can replace the full umbilical. Ugh!
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Old 04-20-2021, 06:14 AM   #11
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If you arenít measuring any power, I know my GMC 2500 has a fuse dedicated to the integrated trailer brakes you can check.
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Old 04-20-2021, 07:05 AM   #12
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Quote:
Originally Posted by dog_and_cat View Post
Thanks for the replies. I will check the wiring/ground best I can today.

TV is a '21 F-150 with integrated OEM brake controller.

Measured V inside the truck connector was less than a volt though I want to recheck this. Any idea what this voltage should vary between?

Hinge cover is on the top side. But when fully inserted the plug never feels super secure.

If there is corrosion inside, would a small shot of di-electric grease or contact cleaner be a possible fix?
A GM in vehicle controller will not provide brake pulses if it doesn't find the brake magnet load it is looking for, so a GM needs to have 2-3 magnet loads minimum to provide brake pulses. Your Ford, I thought, does not have this issue but maybe something changed. I don't have access to a 21 so can't check it. In general if your gain is at 10 and your manual is at full on you should see vehicle battery voltage at the blue wire at the trailer connector (not GM) with trailer not connected. IF Ford now shuts off (I doubt it) then you need 2-3 magnet loads to get it to pulse. Your meter is reading "average voltage" where blue wire is actually a series of "on/off pulses" at 300 pulses per second. As you move the manual lever the pulses go from 0% on time to 99% on time and your "meter" will show you the average voltage, which at full manual and gain of 10 should be vehicle battery voltage with not loads, slightly lower with brake magnets present. I have a 19 Navigator and if the weather is warm this weekend maybe I will take a look and see what a 19 does. Brake controllers I've designed never stop trying to apply the brakes except cycle if a SHORT is detected. The brake controller will generally indicate if a short is detected, which does not sound like this is happening, but a short would result in no blue wire voltage. So if controller detects shorts, check the status screen.
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Old 04-20-2021, 02:19 PM   #13
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2017 30' Classic
Spokane , Washington
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Our 2020 gmc intermittently says check trailer connection. The connection is fine and the wiring seems fine on the 2017 classic 30. Everything worked fine on our Tundra last fall when we last pulled the trailer...Iím stumped. It seems the gmc doesnít like the trailer for some reason.
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Old 04-20-2021, 03:30 PM   #14
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2021 27' Globetrotter
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Thanks again everyone. I pushed the connector in as far as I physically could and I had good brakes all day. We're staying outside of Richmond tonight but I stopped by Airstream of Virginia when we arrived and they were super helpful. Put some di-electric grease in the pins and zip-tied the connector. This will hold me for this trip until I get home and can replace the connector with something better than what AS provides.

I haven't rechecked the truck-side connector but from what I've read it seems that the new F150s don't show a voltage on the brake pin without a trailer connected.

All good for now and thanks for your comments.
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