In January I had a towbar fitted. At the time I didn't have a trailer but when I did attach one some of the lights on the trailer didn't work and the rear nearside side light on the car went out after a few seconds. I had the car checked by a Skoda dealer who said the towbar electrics were at fault. The guy who fitted the tow bar came back and fitted a 'bypass', which seemed to do the trick.

 

However now I can't turn the headlights off, even when the trailer isn't attached. As soon as I turn on the ignition the headlights come on, low beam and so do the rear side lights. The front side lights don't come on now and I don't have any parking lights. When the trailer is fitted and I press the brakes the side lights on the trailer glow more brightly but the brake lights don't work.

 

Can anyone tell me what's going on?

Could be your light switch has burnt tracks, if so its a safety feature so you drive at night!

I had a similar problem with the switch, opened it up and on the pcb burnt tracks, soldered on some by-pass  wires and it now works fine

Don't know what caused it but assumetoo much current passing, a short somewhere perhaps!!

Thanks, I don't have your skills but it's good to know. I'll try to find someone who does.

Sorry to say it, but this looks like another excellent reason NOT to use a by-pass relay system!

The fitting is still under guarantee, is it best to have the by-pass removed? Will that remove the problem?

2 hours ago, TruncatedWorm said:

is it best to have the by-pass removed? Will that remove the problem?

Who knows what the problem is but any in the know would have a dedicated kit installed not a by-pass kit.

 

4 hours ago, TruncatedWorm said:

The fitting is still under guarantee, is it best to have the by-pass removed? Will that remove the problem?

 

I would get the by-pass system removed as soon as possible and replaced with a dedicated wiring kit.
Whether it will cure the problem depends on whether it has damaged the lighting control unit. Hopefully it will.

You need a dedicated towbar electrics wiring loom and have it correctly coded into the Yeti's systems.

 

Bypass relays and scotchlocks always cause problems eventually on modern cars.

 

Get the electrics done properly.

If you get interaction between different sets of lights, it is very often a sign that a common earth connection is bad or missing. 

 

The current from one bulb or set of bulbs cannot flow directly to earth, but finds a path "backwards" through another bulb or bulbs that share the same common earth.

 

This is very commonplace with trailers, where one pin of the trailer plug performs the earthing function for all the trailer lights.  If the pin corrodes or the wire drops off you get the effect above.

 

Since the bulbs are in series, they don't get full voltage and therefore don't glow as brightly as they should.

 

On the Yeti, it may also play havoc with the bulb failure monitoring system.

The fitting is still under guarantee, is it best to have the by-pass removed? Will that remove the problem?

 

Thanks for all the advice. I'll have it checked out but forewarned is forearmed.

The bypass relay was fitted after the problem but the damage had already been done by drawing too much current. Sounds like the fitter had just spliced the trailer socket onto the existing feeds for the rear lights using Scotchlok connectors.

 

I doubt that it will have overloaded the light switch as that simply switches a small control current to the body control module although when in sidelight mode with the ignition off it must drive the sidelights & rear lights so fingers crossed that it is that.

 

Despite all the religious fervour against bypass relays this is actually a very good example of why they should be used, the modern solid state ones draw a lot less quiescent current (although this is their Achilles heel) and are very reliable, but only as reliable as the crappy splice connectors that many use to fit them and require intelligence in where they are located and protected from condensation or leaking rear washer pipes, most I have seen are just thrown behind the side panels.

2 minutes ago, TruncatedWorm said:

The fitting is still under guarantee, is it best to have the by-pass removed? Will that remove the problem?

 

Thanks for all the advice. I'll have it checked out but forewarned is forearmed.

 

We have already said, get the by-pass system removed completely and replace it with a dedicated wiring loom and then get the car correctly reprogrammed.

3 minutes ago, J.R. said:

The bypass relay was fitted after the problem but the damage had already been done by drawing too much current. Sounds like the fitter had just spliced the trailer socket onto the existing feeds for the rear lights using Scotchlok connectors.

 

I doubt that it will have overloaded the light switch as that simply switches a small control current to the body control module although when in sidelight mode with the ignition off it must drive the sidelights & rear lights so fingers crossed that it is that.

 

Despite all the religious fervour against bypass relays this is actually a very good example of why they should be used, the modern solid state ones draw a lot less quiescent current (although this is their Achilles heel) and are very reliable, but only as reliable as the crappy splice connectors that many use to fit them and require intelligence in where they are located and protected from condensation or leaking rear washer pipes, most I have seen are just thrown behind the side panels.

 

Funny, but there have been numerous reports of problems with people who have fitted by-pass systems, sometimes very expensively, but the only problems reported by those using dedicated looms has been with incorrect reprogramming.
And if modern by-pass systems are so good why aren't the likes of VAG, Kia or other manufacturers recommending or selling them?

Yet another red arrow from my admirer, took all of 30 seconds this time, that makes 20

 

To the OP, you have been told, now do as you are told!!!!   

3 minutes ago, Llanigraham said:

 

We have already said, get the by-pass system removed completely and replace it with a dedicated wiring loom and then get the car correctly reprogrammed.

 

This /\ .

 

Rip out the bypass and all the current towbar wiring.

Fit dedicated wiring and have it programmed.

You will then benefit from the Yeti dong the trailer bulb monitoring the parking sensors and lights will work correctly and the stability control will enable "Trailer Stability Assist" when you have a trailer attached 

Llanigraham. I didn't say they were so good, I simply countered your completely incorrect assertion that the OP's problems were another good example of why they should be avoided.

 

I know that you are evangelical about what you have done and want others to do the same, that you have a problem with accepting that people may have other views or experiences but does that really justify constantly awarding me with red down arrows or have I done something else specific that has upset you?

 

I respect your opinions, we are all adults here and should behave like them.

Edited 26 September, 20205 yr by J.R.

My Yeti has dedicated electrics as it has a factory bar but our Octavia has a towbar with bypass relay. 

The Octavia was fine for a year or so but the relay failed and shorted and caused all sorts of issues.

I've still got to sort this out, it's all disconnected at the moment.

23 minutes ago, J.R. said:

Llanigraham. I didn't say they were so good, I simply countered your completely incorrect assertion that the OP's problems were another good example of why they should be avoided.

So if they are not good is that not a reason to avoid them and have the job done properly?
Read what you have written.

My previous Octavia had one fitted and I fitted one to the Yeti, when I realised that they draw a small standby current at all times (needed if you leave your trailer coupled & the sidelights on) I fitted a cut out switch or placed the inline fues in an accessible position to disconnect the power, I only switch the unit on when I am towing.

 

That way it sits there inert and it is physically impossible (isolation relays) for it to disturb the vehicle wiring were it to become soaked etc.

 

I took a lot of time to protect it and used Telecom grade glycerine filled Molex splice connectors to tap into the rear light feeds, in use it draws less than a milliamp from the respective bulb circuit.

4 minutes ago, Urrell said:

So if they are not good is that not a reason to avoid them and have the job done properly?
Read what you have written.

 

Its you and your cohort who should read what I have written and stop attributing quotes to me that I did not say.

 

I did not say that "they were so good", neither did I say that "they are not good".

 

When people have invested a lot of money or time in something it angers them that others may have chosen a less onerous path, live & let live, accept others views, this forum is supposed to be about helping others.

Edited 26 September, 20205 yr by J.R.

And helping others out is advising them, with over 10 years experience, that the by-pass system is not the best system to use on the Yeti, since it does not allow the car to be reprogrammed to allow all the correct systems and circuits to be used, plus it has been known to cause expensive damage.

Therefore I will continue to do so, and if that means I mark your posts as "Not Helpful" so be it.

26 minutes ago, Llanigraham said:

And helping others out is advising them, with over 10 years experience, that the by-pass system is not the best system to use on the Yeti, since it does not allow the car to be reprogrammed to allow all the correct systems and circuits to be used, plus it has been known to cause expensive damage.

Therefore I will continue to do so, and if that means I mark your posts as "Not Helpful" so be it.

 

So you wrote a cheque out 10 years ago and still feel the pain, how many have towbars & electrics have you fitted yourself since then?

 

it has been known to cause expensive damage.

 

Then please give us the benefit of your experience and explain how.

 

I would still like an explanation of why you repeatedly post "not helpfull" to myself and nobody else simply because I did not follow the path that you tell others to, if you disagree with advice that I give in response to peoples requests then say so and explain why instead of the red arrows, preferably without inventing your own recieved wisdom like "it has been known......."

Quite frankly I can't be bothered.
I suggest that if you don't like the way I respond to your sometimes incorrect and ill-advised "advice" you take it up with the Moderators.

I would not bother them with your childishness, all I am asking you to do is stop awarding unwarranted "unhelpfull" red arrows when I post in response to an appeal for help from another contributor, if you believe something I say is incorrect then please explain why.

10 hours ago, J.R. said:

My previous Octavia had one fitted and I fitted one to the Yeti, when I realised that they draw a small standby current at all times (needed if you leave your trailer coupled & the sidelights on) I fitted a cut out switch or placed the inline fues in an accessible position to disconnect the power, I only switch the unit on when I am towing.

 

That way it sits there inert and it is physically impossible (isolation relays) for it to disturb the vehicle wiring were it to become soaked etc.

 

I took a lot of time to protect it and used Telecom grade glycerine filled Molex splice connectors to tap into the rear light feeds, in use it draws less than a milliamp from the respective bulb circuit.

 

I still don't get why you would go to that much time, effort and expense to try and negate the issues with bypass relays when dedicated looms are relatively cheap. Around the price of a couple of tanks of fuel.

 

For that you get proven reliability.

The Yeti doing bulb failure monitoring and foglight switching.

Correct operation of parking sensors.

And most importantly antisnake adaption of the cars stability control