AL-KO ATC Fault

[PaulT]

I have a Bailey Unicorn S2 which I tow with a Volvo XC90. At the start of a recent trip back to the UK I connected up the 13 pin lead and the AL-KO ATC did its usual self-test and the green indicator light came on. As usual on the ferry (and I don’t know why I do it) I disconnected the 13 pin lead and reconnected it prior to getting off the ferry – again all was as normal. On arriving at my destination, none of the interior electrics were working. I checked the fuses and discovered that 2 had blown – the 20amp one marked “van battery” and the 15 amp marked “Car”. I thought that was strange but replaced them – all returned to normal and there were no more problems until the time came to return to France.

I connected up the 13 pin lead and nothing happened – no self-test, no green or red indicator light. Everything else (road lights, fridge, water pump etc) was as normal. I didn’t have time to check things at the time but did when we stopped at various times on the way to the ferry – there was no change. On arriving home I again checked the fuses and none had blown in the caravan. However, one had blown in the car. This is fuse 7 in the load area fuse box and according to the car handbook is the “Towing bracket wiring(30-feed) 15 amp” fuse. I don’t know when this fuse had blown but suspect that it had probably blown at the same time as the others.

Once I replaced this fuse, the ATC did its self test but still no indicator lights.

I’ve examined the small LED light on the draw bar and there appeared to be condensation in it. I’ve disconnected it and cannot get it to light when connected to a 12v supply. However, when I connect a non-LED test bulb to the lead coming from the ATC control box I cannot get it to light when the ATC does its self-test.

My questions to forum members are:

1. Would the LED bulb failing due to water ingress cause the fuses to blow?
2. Is it possible to test a circuit which normally has an LED bulb in it using a halogen bulb?
3. If the indicator light is not green (but not red either) and the system has done its self-test, is the ATC working?
4. Has anyone got any suggestions as to what is wrong? (Please don’t just say to take it to a dealer, they are not that common out here!)

 

[ProfJohnL]

.........................My questions to forum members are:

1. Would the LED bulb failing due to water ingress cause the fuses to blow?
2. Is it possible to test a circuit which normally has an LED bulb in it using a halogen bulb?
3. If the indicator light is not green (but not red either) and the system has done its self-test, is the ATC working?
4. Has anyone got any suggestions as to what is wrong? (Please don’t just say to take it to a dealer, they are not that common out here!)

Hello Paul.
I cant be specific about the root cause of your difficulty but a couple of points do come to mind.

Firstly LED's are sealed semiconductors, and the can't get condensation inside them, so I suspect you are referring to some sort of housing in which ans LED is located. It very unlikely the LED would fail due to water ingress, but what around it might, so without knowing whats inside the housing who knows whats in there ( Well I suppose Al-Ko do :huh:

A normal LED is a unipolar device which will only work whan current flows in one direction. If you connect it up backwards it will not illuminate and you may damage it. They only requires between 1.4 and 3V to run so connecting it directly to 12V may also have damaged it.

LED's use very small currents to operate (10 to 40mA depending on the construction). supplies that run them are ususally current limited, so there would be insufficient current to illuminate a12v halogen bulb. Depending on how the circuit that drives the LED is configured, fitting an over rated bulb could damage the control circuit .

You need to establish what has gone wrong, and with respect what you have done so far suggests you are not familiar with electronics and their limitations. You do need to seek some professional advice.

 

[Dustydog]

Hi Paul
The ATC on our Wyoming failed a few years ago for no apparent reason.On plugging into the car it never went through its self check mode and no light at all.
Fuses were ok but I discovered a very poor earth connection on the towbar socket.Changing the socket and making good all the wires including earth fixed it.
Do you have your ATC handbook?
It contains a very comprehensive diagnostic process that does answer all the questions you raise.
.
It is down loadable directly from Alko website.
https://www.google.co.uk/url?sa=t&rct=j&q=&esrc="s&source=web&cd=3&cad=rja&uact=8&ved=0CDIQFjAC&url=http%3A%2F%2Fwww.al-ko.co.uk%2Fedit%2Ffiles%2Fhandbooks%2Fatc-handbook.pdf&ei=WzNCVNfaN5Sp7AaxiICgBA&usg=AFQjCNFOFOLNm_MZ6_0W2DVFaI5TlFpabg"

 

[PaulT]

Thanks Dustydog, I've got the handbook but it doesn't cover my specific points. The system does it's self check but there are no lights at all.

Prof John - as usual, a concise reply. You are right, it's the LED housing that had the condensation and my thoughts were that the moisture had worked it's way down to where the LED is joined to the wiring and that was where the short had occured (if, in fact, there was a short).

 

[Dustydog]

Paul
LED not working ATC has no power Check push rod
position as shown
LED faulty on page 5 before
continuing journey.
Drive forward to
detect movement to
complete self test
and re check LED.
Remove 12S or 13
Pin plug and wait
5 seconds.
Reconnect plug.
Remove 12S or 13
Pin plug and wait
5 seconds.
Reconnect the plug.
Remove 12S or 13
Pin plug and wait 5
seconds. Reconnect
the plug.
Check for constant
live - refer to system
requirements.
Green (Constant) Ready for journey
Green Ready for journey
Red ATC Error logfile memory
exceeded. Caravan can be
towed, but ATC will not apply
caravan brakes in the event of
instability. See below *
Green Ready for journey
Red (flashing) ATC faulty, and cannot be
driven. Remove push-rod as
shown on page 5. Consult
AL-KO, see back page for
details.
Green Ready for journey
LED not working If power ok, check push rod
position: Red line visible - do
not drive vehicle. Red line not
visible - possible to continue
journey but consult AL-KO see
back page for detail

Sorry for the poor reproduction. If no light and your system still go through its self test on hooking up then maybe the problem is as simple as the LED blown.?
I appreciate until you can get a replacement LED it is hard to go any further.

 

[RogerL]

My memory isn't what it used to be - but wasn't there some sort of Alko ATC fault that required replacement of the LED under warranty - sorry that's so vague.

 

[xtrailman]

The ATC led is a bipolar type and is available from the bailey parts site.

They have been known to fail due to water ingress, to replace look under the A frame and you will see a connector, this connector can also fail from corrosion, mine is contralubed and gets covered by a A frame cover.

A quick way to establish a 12 volt supply to the caravan is to check for charging volts across the caravan battery, the battery uses the same permanent supply, it doesn't however fully prove the ATC is supplied, the car needs to be connected and engine on fast tickover.

If the car has a smart charging system put the headlights on to increase alternator volts.

 

[PaulT]

I've crawled underneath and got the OH to plug the lead into the car. The ATC goes through it's self test, the arm moves in and out and then goes back into it's housing with no red line showing. To my mind it's the LED that's gone but are there any other suggestions?

 

[DeliDave_]

It does sound likely that just the LED has gone but ALko recomend that the ATC is wired dirct from battery with a 20 Amp fuse.Towbar fitter connected mine from rear 12volt point in boot and I had lots of trouble incleuding it blowing fuse halffway through selftest and jamming brakes on.Rewired through from battery with 2.5 sqmm cable with a 20Amp fuse at battery end and had no furthur trouble.It should not be controlled by engine or ignition switch

http://www.al-ko.co.uk/pages/electrical-requirements-4.html
It is important to ensure that the towing electrics meet the operating requirements of ATC to ensure the system works correctly during travel.

ATC requires power direct from the towing vehicle electrics and needs a constant 12 volt supply from either Pin 9 on 13-pin or Pin 4 on 12S 7-Pin electrics. Use a multimeter to confirm that the correct pin position is providing a constant 12V supply regardless of whether the engine is on or off.

ATC also needs a good earth connection and a 20 amp fuse is required for the constant 12V supply to Pin 4 on the 12S socket. If only a single fuse is fitted to supply both pins 4 and 6 on the 12S wiring, the power supply capability of the installation must be checked and a minimum fuse rating of 25 Amps must be used.

 

[PaulT]

After a lot of emails AL-KO confirm that it is just the LED that's blown and it is covered under warranty. Volvo have confirmed that it is ok to replace the 15amp fuse which supplies Pin 9 with a 20 amp fuse.

Hopefully, all will be ok now.

Thanks to everyone for their inputs.

 

[Dustydog]

Thanks for the update Paul.
A good result.

 

[PaulT]

My memory isn't what it used to be - but wasn't there some sort of Alko ATC fault that required replacement of the LED under warranty - sorry that's so vague.

Just thought I'd bring this up to date - it was the LED lead that was at fault and I received a new one recently (thanks Reading Caravans). I've fitted it and all has returned to normal.