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Old 02-13-2020, 02:58 PM   #1
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Tekonsha P3 and testing trailer brakes

I've been having a intermittent issue with trailer brakes being reported as "OUTPUT SHORTED NO BRAKES". The P3 wiring is perfect, you'll have to trust me here Good ground etc. etc. etc.


Using the P3 Help menu I'm able to test and show good output (foot on brakes) 1.8V output current .2 amps and stoplight 13.1 Good to know, not related to the intermittent problem...read on.


The red screen error message on the P3 (output shorted no brakes) only happens when moving. It goes away, everything is peachy for a while.


I've tested the brake magnets (FC26U 2 axle) for proper OHMS and get .9 ohms using a Multimeter probe on position #1 and #2 (Trailer Brakes and Ground) respectively. Good right?


This is a nearly new trailer. Just for drill I installed my spare (new) P3 so that's new.


Batter up.
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Old 02-13-2020, 03:18 PM   #2
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7 way cover on TV hinged at top or bottom?

Possible trailer plug not making the contact it should. It can test ok but while driving wiggling looses contact?

Armchair swags

Gary
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Old 02-13-2020, 03:29 PM   #3
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When you get this message, have you ever tried manually applying the brakes while the error is displayed? If so, what happened?
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Old 02-13-2020, 03:53 PM   #4
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Gary - To the side actually. Toyota Tundra. All the outputs test good and I'm still waiting to get even with you for that favor
David - Yes, good question. When I hit the panic lever the brakes work.


Update > I had Mrs. Too Tall press the panic lever while I held a compass in various locations on all four wheels. The front left wheel shows no sign of magnetic field change in any location and all three other wheels have good magnetic field changes.


For the record according the e-trailer, the hearth of all knowldge worth paying for: The most likely cause for the Open Ground/No Brakes error message you are seeing on your Prodigy P3 brake controller is a bad ground connection to the vehicle battery. You can unplug the flat connector from the rear of the controller and allow the unit to re-set. Inspect the contacts on the wiring harness, particularly the one for the white ground wire, to ensure it is not bent, corroded or damaged.
I will double check this just to be sure.
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Old 02-13-2020, 03:57 PM   #5
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i got that once and once a message " no brakes"

after cleaning the contacts and spraying contact cleaner, the error went away
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Old 02-13-2020, 04:25 PM   #6
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Iíve seen several posts here involving intermittent trailer brake connections. Hinged at bottom connections not as supported as hinged at top IMHO. Now your hinged on the side, left or right? JK

I looked at a newer rig last week and the trailer plug had the V form and the TV outlet is V also. The owner commented how easy / loose fitting the plug was. I let him try a spare pollak plug and he noticed how much tighter feeling it fit. The flat blade was just feeling tighter. I replaced my V contact loosey goosey with the same brand flat blade plug and it hasnít failed any pre trip light or brake connection check.

Just for grins look at your plug and see if the Vís have any spring to them to make tight connection to the TV.

Itís a swag but easily tinkered with.

Weíll cross paths somewhere youíre kinda easy to spot in a crowd.
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Old 02-13-2020, 05:24 PM   #7
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Blow in my ear first eh?
Now your hinged on the side, left or right? JK

Standing behind the truck, the plug cover hinges on the right.


I've looked at those TV connectors and there is no reasonable way to tighten anything up. Most of the play is in the plastic surrounding. The design is kinda course/dumb and think that's not the culprit since I'm getting any brakes = good connection from the TV to trailer.


Ask me in another day when the ground dries up.
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Old 02-14-2020, 10:07 AM   #8
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I have a Tundra with the hinge on the right. When my 7 way jiggles loose, I lose the right tail light connection to the trailer first.
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Old 02-14-2020, 11:06 AM   #9
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Modern brake controllers output a low voltage low current signal on the brake lead to detect the presence of active functional brakes and confirm good continuity in the electrical wiring and connectors. As others have indicated your problem is almost certainly minor intermittent problems with the connection, enough to cause a fault in the low voltage test routine.
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Old 02-14-2020, 11:32 AM   #10
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I got a red "Internal error, no brakes" on my prodigy P-3 while having no trailer connected.
Of course, I was planning to leave the next day, so I purchased another P-3 locally, JIK.
After the truck sat for a while, the problem went away. My trip was uneventful, but I kept the spare controller.
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Old 02-14-2020, 11:53 AM   #11
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Used to get the intermittent short message quite a bit on one trailer and only once (so far) on another. That was with a P-2. New magnet(s) was always the cure.

Granted that I did not do the actual diagnostic work, but that was the result that each shop reported.
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Old 02-14-2020, 12:03 PM   #12
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If all else fails look for a loose ground.





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Old 02-14-2020, 01:27 PM   #13
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Aaaaaand the winner goes to Visa/Mastercard


The brake wire leads were cut a bit too long. After cutting the leads from where they exit the hub (external) and attaching to a 12v battery and seeing NO action from the brake......


Once the hub was open it was pretty obvious the leads were too long, got caught on rotating assembly and were wrecked.


Easy fix. Replace the magnet and freshen up the leads using marine butt connectors of course


Kudos to Dexter for calmly answering questions and obviously good quality parts. Brickbats for sloppy QC assembly.




Warranty claim sent to Dexter. TBC
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Old 02-14-2020, 02:19 PM   #14
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I went thru this last year dealer blamed on TV, car dealer blamed on trailer
Removed trailer wheels and found a faulty wire to brakes Therefore Dexter axel issue
Now fixed
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Old 02-14-2020, 03:41 PM   #15
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Quote:
Originally Posted by Too tall View Post
I've been having a intermittent issue with trailer brakes being reported as "OUTPUT SHORTED NO BRAKES"


I've tested the brake magnets (FC26U 2 axle) for proper OHMS and get .9 ohms using a Multimeter probe on position #1 and #2 (Trailer Brakes and Ground) respectively. Good right?


Batter up.
SCHWINNNG BATTTTTTER SHCWINNNNG

A full count and Mighty Casey has struck out. It's a sad day in Mudville folks.

Oh this is a good one.

Resistance per magnet is about 3.2 ohms (Dexter spec), right?

So four magnets X 3.2 ohms is 12.8 ohms and you only measured 0.9 ohms?

NO DON'T JUMP ALL OVER ME!!!!!!!!

That 12.8 ohms is if the magnets where connected in SERIES but these are connected in parallel, yeah you can search how this is calculated.

Per an online parallel resistance calculator 4 magnets with 3.2 ohms / magnet is 0.8 ohms. But if it's only 3 magnets at 3.2 ohms then the calculated value is 1 ohm resistance.

So Too Tall, your 0.9 ohms measured value is right in there for a 4 magnet or 3 magnet system !!!!!! The value didn't draw attention to a magnet wire rubbing the magnet drum face.

The wire grounding out maybe goes hand in hand with your controller stating

OUTPUT SHORTED is your controller smart enough to report OUTPUT OPEN?

My swag was just that, based on simplest possible concern, the famous RIGHT HAND hinged TV 7 way outlet!

Oh this is a whole lot better than do I need WD hitch to tow my SSS with a RRR ?

I like it!

Gary
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Old 02-14-2020, 03:51 PM   #16
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Thanks Gary and you are a good mechanic who follow the principle of fix the easy stuff first.


This >> OUTPUT SHORTED is your controller smart enough to report OUTPUT OPEN?


Bingo. The mighty P3 did it's J O B and was screaming at me the answer.


LOl I'm really not that smart. I got the resistance numbers direct from a tech. at Tekhonsa.



Anywho, it actually feels good to take things apart and know it is done right. Perhaps equally good to know why things go wrong.
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Old 02-14-2020, 04:17 PM   #17
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Nice catch Too Tall, I learned something today! Thanks.
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Old 02-14-2020, 04:45 PM   #18
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And folks just as an FYI that is what a never lube axle shaft looks like.


FYI FYI

I mounted an entire Dexter disc brake system on that type axle stem last year as a letís see how it fits. Yeah the entire backing plate comes off first.
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Old 02-18-2020, 07:19 AM   #19
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If you found this thread you might want to know that 3rd gen Tundras use a Hopkins wiring kit (inset bumper) #40974. Just for drill I replaced mine hoping for a better fitting trailer plug...it's a little better and I'm $20 poorer
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