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Tow bar electrics issue

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Hi

I have had a TEB7AS isolation relay module fitted to my 2014 Skoda Fabia for many years and have had no lighting issues whatever when I plug in to the 7 pin tow bar socket whether it be bike carriers or various trailers.

However I now have an issue with a new tow ball bike carrier.

All the lights work for a short while – maybe 20 seconds - then the CAN Bus bulb monitoring light comes on the dash and the module buzzer tone changes to more of a screech and the l/h winkers on the rack and car stop working, then after a further 20 seconds or so, all the winkers on rack and car stop working.

If I plug in my 7 pin lighting board into the car 7 pin socket everything is fine.

If I plug the rack inc 13 pin adapter into my 7 pin Motorhome, it works fine.

I have to remove and replace the indicator fuse to get them working again, then the same thing happens again.

I don’t understand how the car bulb monitoring light can come on and the ECU shut down the winkers, when it’s supposedly isolated and the car doesn’t know there’s a bike rack on there.

Please help

Andrew
 
It must know something is plugged in, or it would act like nothing was there.

Does your vehicle socket rotate down for plugging in? I had one like that once, and the socket was only operable when it was swung down.

Is the problem unit LED bulbs and the others that work old filement?
A 2014 vehicle unit wouldn’t be designed for a low load.

I’m guessing here. I can’t even sort my own caravans lights.
 
It must know something is plugged in, or it would act like nothing was there.

Does your vehicle socket rotate down for plugging in? I had one like that once, and the socket was only operable when it was swung down.

Is the problem unit LED bulbs and the others that work old filement?
A 2014 vehicle unit wouldn’t be designed for a low load.

I’m guessing here. I can’t even sort my own caravans lights.
I agree, although the tow bar should be isolated by relays, the car is still sensing a fault. No its not a rotate down 7 pin socket, Bizarrely the New carrier is filament bulbs but my old lighting board, which works fine, is LED.
 
I agree, although the tow bar should be isolated by relays, the car is still sensing a fault. No its not a rotate down 7 pin socket, Bizarrely the New carrier is filament bulbs but my old lighting board, which works fine, is LED.
Are all the previous ones you have used without problems been led ?
 
Is this because the ECU/CAN bus is voltage sensing? If so I suspect with the engine running it will be about 14v, but I will check tomorrow.
What could cause a car voltage anomoly only with this carrier attached?
 
Is this because the ECU/CAN bus is voltage sensing? If so I suspect with the engine running it will be about 14v, but I will check tomorrow.
What could cause a car voltage anomoly only with this carrier attached?
Maybe drawing too much current ? Have you tried different modes, like trying with only indicators or only brake lights ?
 
Maybe drawing too much current ? Have you tried different modes, like trying with only indicators or only brake lights ?
Yes, it only seems to be the indicators that are affected on carrier and car, all others unaffected. Are you thinking replace those 2 21w bulbs with LED bulbs? The filament shod trailers and lighting boards also have 2 x 21W bulbs and they work fine on this car.
 
Yes, it only seems to be the indicators that are affected on carrier and car, all others unaffected. Are you thinking replace those 2 21w bulbs with LED bulbs? The filament shod trailers and lighting boards also have 2 x 21W bulbs and they work fine on this car.
You could certainly try LED bulbs
 
The better way would be to actually test the trailer board, though, both for wiring and current draw.
 
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