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Old 08-03-2021, 04:35 PM   #1
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Brake controller shorts when I apply the brakes

teshonka brake controller says “overloaded” when i press brakes. was working until a very rough 5-mile construction zone. have triple checked all the wires from controller all the way to inside the trailer. 7-pin good all the way.

1972 sovereign. inside trailer it looks like black cable to brakes and orange cable to emergency brake. it appears that the white wire to brakes doesn’t have ground. in middle of road trip in rural wyoming. to get brakes working i’m going to wire all 4 brake white wires to frame for grounding.

thoughts?
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Old 08-03-2021, 04:46 PM   #2
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Excessive brake circuit current draw causing overload.

Brake magnet worn and magnet coil windings shorting against drum during actuation?

Brake positive wire is shorting on frame somewhere?

Sounds like brake circuit needs some time with a meter and brake inspection.

Certified from the couch SWAG’s

Gary
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Old 08-03-2021, 06:37 PM   #3
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I would not wire the brakes to the frame. It is a 2 wire system. Not grounded. Find the broken wire and fix it
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Old 08-03-2021, 11:27 PM   #4
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Quote:
Originally Posted by GCinSC2 View Post
Excessive brake circuit current draw causing overload.

Brake magnet worn and magnet coil windings shorting against drum during actuation?

Brake positive wire is shorting on frame somewhere?

Sounds like brake circuit needs some time with a meter and brake inspection.

Certified from the couch SWAG’s

Gary


brake positive wire would be hard to diagnose i would think since this only happens when i’m driving. any suggestions? i have no idea where the wire goes between the 7-pin and brakes. wires from 7-pin appear to be black and orange.

brake magnet worn? these are new brakes installed at Oasis RV in Tucson and this is the very first trip. This issue didn’t start until a particularly rough stretch of construction on US Hwy 40. this is way outside my previous experience but i’ve limped to a place i can spend a few days teasing it out. is there a way to isolate that problem without removing tires and brakes?
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Old 08-03-2021, 11:28 PM   #5
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Quote:
Originally Posted by Bill M. View Post
I would not wire the brakes to the frame. It is a 2 wire system. Not grounded. Find the broken wire and fix it


thanks for the straight reply. not sure how to diagnose a wire that may only be shorting at speed. it works even at low speed but as soon as it’s 10mph or more the controller reports overload when i press brakes.
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Old 08-03-2021, 11:41 PM   #6
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Quote:
Originally Posted by GCinSC2 View Post
Excessive brake circuit current draw causing overload.

Brake magnet worn and magnet coil windings shorting against drum during actuation?

Brake positive wire is shorting on frame somewhere?

Sounds like brake circuit needs some time with a meter and brake inspection.

Certified from the couch SWAG’s

Gary


based on https://www.etrailer.com/question-15624.html, going to disconnect all the trailer wires from the brakes and check resistance through the two wires coming out of the brakes.
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Old 08-03-2021, 11:50 PM   #7
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where does the brake wire(s) generally run after the 7-pin? i see an orange and a black wire. looking towards the tow vehicle they both disappear low off to the left. if i ran a new one, do all four brake wires need to come off the main wire or do right/left branch off and then hit the brakes in serial, or can they all be wires in serial?
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Old 08-04-2021, 12:13 AM   #8
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Quote:
Originally Posted by aaryno View Post
where does the brake wire(s) generally run after the 7-pin? i see an orange and a black wire. looking towards the tow vehicle they both disappear low off to the left. if i ran a new one, do all four brake wires need to come off the main wire or do right/left branch off and then hit the brakes in serial, or can they all be wires in serial?


this thread suggests the brake wire goes from 7-pin in wall on street side to the first axle and then goes through floor and across to the center of the belly between the axles where there is a 4-way junction with wires to all four wheels. i don’t have a rivet gun with me so not sure the best approach here.

https://www.airforums.com/forums/f43...ns-150043.html
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Old 08-04-2021, 05:24 AM   #9
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Quote:
Originally Posted by aaryno View Post
brake magnet worn? these are new brakes installed at Oasis RV in Tucson and this is the very first trip. This issue didn’t start until a particularly rough stretch of construction on US Hwy 40. this is way outside my previous experience but i’ve limped to a place i can spend a few days teasing it out. is there a way to isolate that problem without removing tires and brakes?
New brakes, not mentioned in 1st post. Any chance to have the installer review their work?

Yes you can use a multimeter on the 7 way plug checking resistance in Ohms between the brake terminal in the plug and ground either thru the plug again or to trailer chassis ground. Dexter service manual LIT-001-00 has info on page 21 https://www.dexteraxle.com/Resources...mily=&keyword=
Each magnet has about 3 Ohms resistance connected in parallel from the brake power wire. If you have 4 brakes because its a parallel connection you only have about 0.75 Ohms resistance. It doesn't add like a series connection .
If you can check the resistance good, if not can you just slide under the trailer and look for obvious what's that type of repairs to the wiring in particular any bare spots in the insulation.

As far as color code yes likely when the trailer was built a color code was used but now if the cable or wire has been replaced it is what it is.

Gary

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Old 08-04-2021, 05:49 AM   #10
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Have you checked the full length of the visible wires going to all four brake backing plates? If this is happening at speed, it could be something quite simple like a bit of insulation worn off making contact with the frame, or even a stray strand of the wire which was left outside a butt connector when the new brakes were installed. Get going fast enough and that get pushed against the frame. Start simple.

On my trailer I had some brake issues and eventually I disconnected all eight wires from the brakes. Then I was able to confirm that there was a good ground to four of them (one per wheel) and that there was good continuity between the other four and the proper pin on the 7-way plug. Also was able to confirm that there was no short to ground from the positive side of the brake wiring. After all that was confirmed, I was able to look elsewhere for problems.

Since you're is a problem only at speed, it sounds like you have something which was left exposed which is finding a ground connection.
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Old 08-04-2021, 09:40 AM   #11
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Hi

With newly rebuilt brakes, I'd bet on the wires going from the brakes to the trailer. They should be visible if you crawl under the trailer and look at the "back" ( = under trailer) side of the wheel area. I suspect you will find a wire nut missing and the wire dangling in the wind. Wind blows the wrong way and it shorts.

If it's an issue at the brake, a quick check might be to roll along on gravel. Apply the brakes with the controller. The wheel that does not lock up is the one you are after. This assumes that the wire nut is gone and there is no longer a connection there .... might be the case ... might not be.

Bob
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Old 08-06-2021, 07:45 AM   #12
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quick update - last time i was ready to check ohms for each brake but the last easy thing to check was the emergency breakaway switch. after disconnecting that i have had no issues.
so far so good.
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Old 08-07-2021, 08:38 AM   #13
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Hi

If cycling the breakaway switch seems to have solved the issue ... give it a good flush with something like WD-40. Don't be bashful. If you use a whole can, that's fine . I'd also see about putting a replacement switch on order ....

Bob
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Old 08-08-2021, 04:39 PM   #14
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Hi

If cycling the breakaway switch seems to have solved the issue ... give it a good flush with something like WD-40. Don't be bashful. If you use a whole can, that's fine . I'd also see about putting a replacement switch on order ....

Bob


where does the orange wire go? does it go straight to the breakaway line? i thought i read somewhere that it goes all the way to the battery. is there a wiring diagram somewhere?
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Old 08-09-2021, 08:59 AM   #15
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where does the orange wire go? does it go straight to the breakaway line? i thought i read somewhere that it goes all the way to the battery. is there a wiring diagram somewhere?
Hi

Well, if you can find the manuals for your 1972 .... it should be in there ...

In modern trailers, there are two wires, one goes to the brake wiring. The other goes to the DC bus bar. Both seem to run to roughly the same area to make the connection in my trailer. Not a clue where they put this or that "back in the day".

Bob
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Old 08-09-2021, 02:24 PM   #16
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https://www.airstream.com/owners/manuals/year/1972/

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Old 08-09-2021, 02:35 PM   #17
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Airstream (and other RV makers) are not as organized as the automotive industry. Especially 40 or 50 years ago or more. Travel trailers are much less complex than a car or light truck. Plus the travel trailer industry build about 1/10th of the automotive industry. (or less)

Because of that and the lack of standardization wiring can be all kinds of a mystery. To compound that, at one time Airstream wired their pigtails to the TV differently than today's norm.

Then add in modifications or technician repairs and you may have a box of chocolates!

A reference to wire color may or may not be relevant.

And as a suggestion not related to the above ... if you are replacing any wiring, I would recommend using at least one size larger wire. Wire size is a thing that can be a cost savings item for a manufacturer. It will work for a decade or so, and may not be the best for later years. If you are working with 16 gauge wire, a move to 14 gauge would be a longer term solution if making a repair.

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Old 08-10-2021, 07:18 AM   #18
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Action is correct in his comments. You need to also consider the wire "length" as well as the wire "gauge". A wire has "resistance" which means it drops the voltage applied from the brake controller, thus the greater the drop, the less the voltage across the brake magnets.

https://www.offroaders.com/technical...more%20rows%20

You may want to view the "Length of Wire" table like above to make your wire gauge decisions. In typical trailer wiring, the main brake wire from the trailer connector to the location where they "split apart" to the individual brakes should likely be 12 gauge if the distance exceeds 10 feet in the referenced chart, 14 gauge if less than 10 ft. If using something like an asymmetric electronic sway controller this distance would be from trailer connector to the sway controller, where left brakes are powered by one wire and right brakes by another wire leaving the sway controller. Since half the current would be flowing to left and right sides assume 8 amps to each side for a double axle.
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