Electrical Alko ESC fault diagnosis

Jan 13, 2017
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Currently on the big Lap
#1
Just a quick note on the operation of the ESC system when diagnosing a fault not mentioned in the manual. I spent a couple of weeks worming (or rather whaling these days) under the van trying to track down what happened (permanent red light). I eventually phoned Alko and apparently after 10 failed attempts the module enters permanent fault mode and needs to be returned to ALKO for reset. This omission from the manual probably cost me 10 hours of 'whaling' and had me doubting my already limited electrical diagnosis skills.

I have my ESC wired into the 7 pin so every time I unplugged and plugged it in (eventually I found a failed brake magnet) the esc counted that as a failed attempt. So this is another good reason to run a dedicated Anderson plug for the esc system. Otherwise get under the van and unplug the connector to the module located just behind the vans rear axel (centre) prior to diagnosing the underlying (brake magnet/wiring) fault.

Other than 4 screws the module is attached to the van (on my Jayco anyway) with what appears to be Sikaflex 11fc and is a bugger to get off.... can't get right around it with a renovator w/ the plain (no teeth) blade.


This is the diagnosis protocol I used to find the underlying (brake) fault which is the best I came across
https://www.etrailer.com/faq-testing-trailer-brake-magnets-for-proper-function.aspx

This is the Alko esc component
https://www.alko.com.au/wp-content/uploads/2016/02/AL-KO_ESC_User_Manual_V10LR.pdf
 
Jan 13, 2017
51
73
18
Currently on the big Lap
#3
Using wire trace was a good idea - I managed to lever it off in the meantime.

This final section (below) of the ESC loom ended up being the culprit. I was led to believe from ALKO (who have been very helpful) this is a Jayco only part which contains a diode for each brake wire (therefore 2x) which prevents current travelling from the brake controller (and the breakaway unit) to the ESC module but allows the ESC unit to activate the brakes. I can only assume this is to stop the diagnostic currents from the brake controller and breakaway systems interfering with the ESC diagnostic current (where ESC is wired to pin 2 - aux/reverse light)... not sure.

The symptoms/conditions/events were:
Brake controller diagnostic - Good
ESC unit - Bad (red light)
Good volts at ESC unit
Immediately following shorted brake magnet - brake system measured at plug pulling 28amps (engine/alternator off) whereas typically would carry 10-12amps (engine on 12-14amps).

Interpreting the ESC manual a red light can occur in 3 broad ways - 1) insufficient volts (I assume something beyond 10.5 -11 or so) or 2) brakes not detected or 3) failed ESC unit. In my case the diodes (both) appear to have failed therefore the ESC could not detect brakes. I couldn't get a resistance reading in either direction on the brake wires on the failed loom.

Diode pack is visible mid loom.... partially melted/buckled
ESC loom.JPG
 
Likes: Drover
Jan 13, 2017
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73
18
Currently on the big Lap
#5
I just got a new loom ... ALKO took pity on me and gave me one gratis since my caravan was quite new. Although it occurred to me subsequently that they won't want to a failed brake component going through the Jayco order system on quite new vans ... although in my case this was very likely caused by the magnet short which in turn was caused by an idiot. The idiot had just serviced the hubs himself ... took it on a 30km run felt the hub on one of the brakes hot so without jacking the wheel adjusted the by a couple of clicks which was likely the wrong way! The idiot then continued to drive a further 150kms on the highway until the first exit with no brakes. Lucky he drives like a granny @ 6.5t trainweight.

brake magnet.JPG
 

Drover

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Nov 7, 2013
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#6
I would say something was causing power to be applied to the magnet, it was applying the brakes and cooking things, adjusting the shoes wouldn't and couldn't cause the magnet to operate and that one was certainly working, your manual adjustment of the shoes only changes the distance between shoes and drum and has nothing to do with the function of the magnet.

So the idiot really wasn't.............. when you fit it back together test the wires at the hub for continuity with a meter one probe on a wire other to earth if its live with no foot on brake you have a problem it should be dead until foot on anchor, you can cheat on this by just pulling the brake safe pin also. I think I would be going around all of them and testing everything.
 
Likes: skippy
Jan 13, 2017
51
73
18
Currently on the big Lap
#7
My thought was that the magnet is in constant contact with the drum albeit lightly courtesy of the yellow spring. So the shoes engaged (via bad adjustment) the drum heating it up ...then the drum heated the magnet and not sure if applying the brakes finally sealed their fate or if it happened before that. Anyway nice to hear somebody on my side since swmbo has seized the opportunity to downgrade my operational status around the house to 'non-functional' ... whereby electricians are now called to change lightbulbs!
 

Drover

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Nov 7, 2013
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#8
No mate you are certainly in the clear, you could wind the shoes up hard and the magnet would still be basically swinging in the breeze, when the magnet is activated it will grab the drum and the actuating lever will, via the cam push the shoes onto the brkaing surface if you haven't set the shoes correctly they won't do a thing but if the brake controller has a wobbly or a short in the 7/12 pin happens the brakes will activate..... brake adjustment won't cause the magnet to wear away or melt, even a drum meltdown will just melt the wires, blow a fuse...... so carry on your safe to change bulbs.

I found a 7 pin that due to poor connections the brakes would come on with the parking lights..... not fully though just enough to drag.

Always adjust brakes with wheel off the ground, on ground is a bit like Russian Roulette, with wheel off ground and brakes adjusted nicely the wheel may only spin 1.5 turns at most, may make a noise but thats okay, apply a couple of times once you get moving to bed in...... I have heard of ESC systems applying one brake when they have a hissy....... but not having had the system I haven't done a 101 on them yet.

Have a look at this link https://www.caravansplus.com.au/guides/which-electric-brake-controller-will-suit-me-a-9.html#2
if you scroll down to the section "How do electric brakes work?" you will find a good explanation and a giff to show you...
 
Likes: Lap Dog
Jan 13, 2017
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Currently on the big Lap
#9
Drover consider yourself hired as part of the defence team as expert witness. I ended up rewiring the tug and van brakes, aux (to esc via breakaway) and earth wires to 6mm + van chassis earth .... so can’t test your theory. I must say I was a little surprised with how noddy the Jayco system appeared ... Not to say they don’t know what they are doing.

Thanks
 
Likes: Drover
Jan 13, 2017
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Currently on the big Lap
#10
Sorry just to pick up one final point concerning the operation of esc system and a misconception. The esc system does not control one side wheels or the other to control van sway .... it is simply a blunt instrument and equivalent to pressing the van brake override from the brake controller. This is evident from the photo of the loom above whereby while 2x brake wires exit the loom from the esc module (travelling back up the loom) they meet prior to the next connector (notice only one brake/blue wire entering the connector). Whilst this is a Jayco loom I doubt any manufacturer would wire in an attempt to control one sides van brakes or the other ... first the controller and wiring on the tug is sent down one wire, second where 2x wires are used joining the wires at the end of their brake run is a built in redundancy against failure of one of the wires thirdly it’s just plain dangerous to have the ability for one part of the loom to fail and brakes on one side of the van to operate and the others not fourthly if it was attempted diodes would need to be placed immediately after the wires split from the brake controller wire to prevent this join becoming a conduit for the current to travel back down to activate the brakes on the other side of the van... diodes in this position would be an unacceptable point of potential failure.

Therefore I don’t see it as possible that the esc unit could activate the brakes on one wheel and not another (as noted)... barring a wiring fault which should have been evident from normal brake operation.
 

Drover

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#11
I was only referring to something I had read about only one side operating but thinking back it was a fault in the fitting of the unit, was awhile ago and yes some of tge wiring does seem somewhat ordinary and not only Jayco.... Knowing how to adjust, check and diagnose brakes and bearings is really a must if you go touring, its not rocket science just requires some common sense and a strong desire not to die or sit on the side of road 500 miles from no where...

Dont forget to check the wheel nuts.