I have now tried two different  way bypass units and neither will enable to fog light to work on the trailer. The 7 way bypass instructions say dont connect the tail lights if the vehicle has shared brake/tail or fog/tail, this vehicle has both. The stops work fine on both units, the tails only work on one, the reverse only works on the other, the indicators work on both units, it makes no sense!
Can anyone here shed any light on this situation?

I'd contact the bypass kit manufactures and see what they suggest?

 

Otherwise maybe ask a local towbar installer if they have any experience with the Octavia and what kit they would recommend.

 

Personally, this is one of the reasons I prefer dedicated kits over bypass style on modern cars 

1 minute ago, langers2k said:

I'd contact the bypass kit manufactures and see what they suggest?

 

Otherwise maybe ask a local towbar installer if they have any experience with the Octavia and what kit they would recommend.

 

Personally, this is one of the reasons I prefer dedicated kits over bypass style on modern cars 

 A dedicated kit would require coding I believe so I wouldnt be able to fit that myself, but I can check with the manufactures, if I can get in contact with them.

I have messaged both manufactures of the products I have and will see what they have to say.

I will try a last ditch attempt to get things to work using a combination of both relays if I can though. Im thinking if I only try the fog on the unit that also works the reverse light but have the stop and tails on the other I might just get something working. It wont be a standard set up, but I cant see it overloading the car as its still only operating the same amount of lights as it would from one unit.

Assuming you did need coding, there are plenty of member with VCDS that are happy to do coding if required, it'll just depend where in England you are to who is local

 

Anyway, I assume you're still trying to use the TEB7AS mentioned in your other thread? Not sure what the other module you've tried is?

 

In which case, it seems others have had it working on a MK2 Octavia:

- https://www.briskoda.net/forums/topic/209000-tow-bar-bypass-relay-wiring/?do=findComment&comment=2470657

- https://www.briskoda.net/forums/topic/179204-mkii-fog-light/?do=findComment&comment=2155362

 

 

I'd wire it up as:

- Yellow, left indicator

- Green, right indicator

- Red, brake light (either side)

- Blue, fog light (drivers side as stock cars only have one side enabled)

- Grey, reverse light (either side)

- Black, securely taped up

- Brown, securely taped up

- White, a good clean earth point!

 

You've not mentioned if you're using a single 7 pin (12N), dual 7 pin (12N+12S) or a 13 pin socket.

 

Therefore, I'd suggest you use the screw terminals on the TEB7AS to check which are getting power.

 

Colours based from this PDF: http://www.towbarsdirect.co.uk/images/M7-WK7.pdf

26 minutes ago, langers2k said:

Assuming you did need coding, there are plenty of member with VCDS that are happy to do coding if required, it'll just depend where in England you are to who is local

 

Anyway, I assume you're still trying to use the TEB7AS mentioned in your other thread? Not sure what the other module you've tried is?

 

In which case, it seems others have had it working on a MK2 Octavia:

- https://www.briskoda.net/forums/topic/209000-tow-bar-bypass-relay-wiring/?do=findComment&comment=2470657

- https://www.briskoda.net/forums/topic/179204-mkii-fog-light/?do=findComment&comment=2155362

 

 

I'd wire it up as:

- Yellow, left indicator

- Green, right indicator

- Red, brake light (either side)

- Blue, fog light (drivers side as stock cars only have one side enabled)

- Grey, reverse light (either side)

- Black, securely taped up

- Brown, securely taped up

- White, a good clean earth point!

 

You've not mentioned if you're using a single 7 pin (12N), dual 7 pin (12N+12S) or a 13 pin socket.

 

Therefore, I'd suggest you use the screw terminals on the TEB7AS to check which are getting power.

 

Colours based from this PDF: http://www.towbarsdirect.co.uk/images/M7-WK7.pdf

Thanks I use passenger side for fogs! thanks for what you said I can try with that and see how it goes. The other model is Smart Logic 7 Way Bypass Towing Relay 12N Towbar Wiring Canbus Ring RCT485. 
I will let you know if I need coding.
BTW as Im only using lights at the moment I have been using a switched power source from the boot area, which is fine for the relay of course, but I had a look at the fuese box today and Im wondering where I would need to join the power for caravan battery, fridge and internal lights? And how it would be connected, Im assuming that a much better connector than the ones used to connect the relay wires to the car light wires?

On 29/01/2021 at 20:49, langers2k said:

Assuming you did need coding, there are plenty of member with VCDS that are happy to do coding if required, it'll just depend where in England you are to who is local

 

Anyway, I assume you're still trying to use the TEB7AS mentioned in your other thread? Not sure what the other module you've tried is?

 

In which case, it seems others have had it working on a MK2 Octavia:

- https://www.briskoda.net/forums/topic/209000-tow-bar-bypass-relay-wiring/?do=findComment&comment=2470657

- https://www.briskoda.net/forums/topic/179204-mkii-fog-light/?do=findComment&comment=2155362

 

 

I'd wire it up as:

- Yellow, left indicator

- Green, right indicator

- Red, brake light (either side)

- Blue, fog light (drivers side as stock cars only have one side enabled)

- Grey, reverse light (either side)

- Black, securely taped up

- Brown, securely taped up

- White, a good clean earth point!

 

You've not mentioned if you're using a single 7 pin (12N), dual 7 pin (12N+12S) or a 13 pin socket.

 

Therefore, I'd suggest you use the screw terminals on the TEB7AS to check which are getting power.

 

Colours based from this PDF: http://www.towbarsdirect.co.uk/images/M7-WK7.pdf

Hi an update, I managed to get all the lights working with the first 7 way bypass unit, I then tried with the second and all but the tail lights worked. So I used the first unit. 

I also got a cable from the back of the car to the front to allow the other caravan power options, battery charging, fridge, internal lights ect.

I still don't know how to go about connecting that to the 12v supply behind the fuse box, to get a clean unfused supply thats powerful enough. 

I would like some advice about how best to proceed with that.

I have included a picture of where Im at with it, there are two inline fuses in parallel 15 amp each totalling 30amp. 

I have found this kit https://www.ebay.co.uk/itm/Car-Add-A-Circuit-Piggy-Back-Fuse-Tap-Mini-Blade-Fuse-Holder-120x-5-30-Amp-Fuse/123197128389?hash=item1caf1efec5:g:lAUAAOSwHrlcI9CT Is it a good idea for installing the permanent 12v for caravan electrics into my car fuse box?

15 hours ago, lotrjw said:

 

I still don't know how to go about connecting that to the 12v supply behind the fuse box, to get a clean unfused supply thats powerful enough. 

I would like some advice about how best to proceed with that.

 

NEVER run an unfused cable. Many car fires are  caused by amateurs running a cable from the battery or other sources in the car without a fuse to protect the cable. 

You have the cable in the right place now so it is just a matter of connection to an appropriate fuseholder that is not being used.  By appropriate, I mean one that is capable of the full current you want to take and has the necessary switching - for example, do you want it to be permanently live, only available when the key is in the ignition, or only when the ignition is on or engine running? Fuses are grouped in the fusebox in this way. 

Many auto electricians run the trailer wiring to a spare fuse position in the engine fusebox. What you cannot do is run the cable directly to the battery. The fuse is there to protect the cable, not the load. Fuses to protect the load must be at the other end of the cable and lower rated.

If in any doubt, get an auto electrician to finalise the wiring.

2 hours ago, pikpilot said:

 

NEVER run an unfused cable. Many car fires are  caused by amateurs running a cable from the battery or other sources in the car without a fuse to protect the cable. 

You have the cable in the right place now so it is just a matter of connection to an appropriate fuseholder that is not being used.  By appropriate, I mean one that is capable of the full current you want to take and has the necessary switching - for example, do you want it to be permanently live, only available when the key is in the ignition, or only when the ignition is on or engine running? Fuses are grouped in the fusebox in this way. 

Many auto electricians run the trailer wiring to a spare fuse position in the engine fusebox. What you cannot do is run the cable directly to the battery. The fuse is there to protect the cable, not the load. Fuses to protect the load must be at the other end of the cable and lower rated.

If in any doubt, get an auto electrician to finalise the wiring.

So can use something like this: https://go.skimresources.com/?id=38947X1001323&isjs=1&jv=14.4.0-stackpath&sref=https%3A%2F%2Fwww.briskoda.net%2Fforums%2Ftopic%2F489678-skoda-octavia-mk2-issues-with-wiring-for-trailers%2F%3Ftab%3Dcomments%23comment-5500444&url=https%3A%2F%2Fwww.ebay.co.uk%2Fitm%2FCar-Add-A-Circuit-Piggy-Back-Fuse-Tap-Mini-Blade-Fuse-Holder-120x-5-30-Amp-Fuse%2F123197128389%3Fhash%3Ditem1caf1efec5%3Ag%3AlAUAAOSwHrlcI9CT&xguid=&xs=1&xtz=0&xuuid=dd7fd3ee3a9cb2da367b500fd6365116&xjsf=other_click__contextmenu [2] so that the cable is protected? will there be enough power off the fuse box for it?

Yes you use one of these, and for small loads such as a camera this way to go but not if you have a large current such as 30A.

It is important that all cables between the the 30A load and the battery which see 30A have to be rated for that. Just connecting the piggyback connector to a random fuse position could overload wiring elsewhere, or more likely, blowing a lower current fuse further upstream.

 

Your best bet is to find a circuit that is already rated for such a load, such as the aux supply/cigar lighter and piggy back on that. Your driver's handbook/user manual that came with car will tell you which fuse number and its location. These change with model year and trim level.

 

Make sure that you buy the correct type of piggyback fuse holder for the fuse position you want to use. The one in your link is for a mini fuse rather than the more common larger style. Also, if the wire on the piggyback looks small (like the one you showed) it is not likely to rated for continuous 30A.

1 hour ago, pikpilot said:

Yes you use one of these, and for small loads such as a camera this way to go but not if you have a large current such as 30A.

It is important that all cables between the the 30A load and the battery which see 30A have to be rated for that. Just connecting the piggyback connector to a random fuse position could overload wiring elsewhere, or more likely, blowing a lower current fuse further upstream.

 

Your best bet is to find a circuit that is already rated for such a load, such as the aux supply/cigar lighter and piggy back on that. Your driver's handbook/user manual that came with car will tell you which fuse number and its location. These change with model year and trim level.

 

Make sure that you buy the correct type of piggyback fuse holder for the fuse position you want to use. The one in your link is for a mini fuse rather than the more common larger style. Also, if the wire on the piggyback looks small (like the one you showed) it is not likely to rated for continuous 30A.

Could I use 2 of them in parallel with 15 amp fuses to create a 30 amp total or would I be best buying a larger 30 amp piggyback one?

6 hours ago, lotrjw said:

Could I use 2 of them in parallel with 15 amp fuses to create a 30 amp total or would I be best buying a larger 30 amp piggyback one?

 

Although two cables can be put in parallel, they should be both be connected to the same double rated fuse.

 

So, yes, you need a 30A piggyback to match the fuse position you are using and secondly you need to use a fuse position that is rated for the current.

Don't forget that your chosen position in the fusebox will see the sum of your load current plus the current in the other fuse at that location so you can only use a piggyback if you will not exceed the limits of the upstream fuse. So ok if you use say, the cigar lighter fuse as that is intermittent use.

 

You can understand now why it is normal to run a 30 A cable from the tow bar socket directly to a dedicated fuse in the engine bay fuse box if you intent to supply a caravan which has high electrical loading.

 

 

Edited 2 February, 20215 yr by pikpilot
typo

I took mine from a spare terminal on the busbar on the battery fuseboard (cant recall the name for it) eye terminal directly to a 30 amp in line fuseholder and then on to the towing relay, a little bit further to run but neater and more professional than how many tap into the dashpanel fuseboard.

 

In fact it had been connected by a garage for the previous owner directly to the battery terminal was unfused and looked a real bodge, I disconnected it to find out what it was and everything still worked so was initially a mystery, a long time later when I first towed & tested the lights before leaving I found what it had been for but not until after loats of head scratching. It was at that point I made the proper connection to the busbar which I think might be called terminal 30.

 

As has been said a fuse to protect the wiring at the point of connection is essential, it has a second purpose in that it can be removed when not towing to reduce the parasitic battery drain, the older relays take more current than all the vehicle standby systems 24/7 so reduce the battery autonomy by 50% +, the later ones are better but still not good, if any water gets onto the relay from say the rear washer pipe detaching when frozen then you will have big current draw problems, I prefer to leave the relay unpowered.

 

On the MK2 I removed the fuse, on my Yeti (connected to the rear power socket)  can do that and also flip a switch, both are just accessible in the rear recess.

20 minutes ago, J.R. said:

I took mine from a spare terminal on the busbar on the battery fuseboard (cant recall the name for it) eye terminal directly to a 30 amp in line fuseholder and then on to the towing relay, a little bit further to run but neater and more professional than how many tap into the dashpanel fuseboard.

 

In fact it had been connected by a garage for the previous owner directly to the battery terminal was unfused and looked a real bodge, I disconnected it to find out what it was and everything still worked so was initially a mystery, a long time later when I first towed & tested the lights before leaving I found what it had been for but not until after loats of head scratching. It was at that point I made the proper connection to the busbar which I think might be called terminal 30.

 

As has been said a fuse to protect the wiring at the point of connection is essential, it has a second purpose in that it can be removed when not towing to reduce the parasitic battery drain, the older relays take more current than all the vehicle standby systems 24/7 so reduce the battery autonomy by 50% +, the later ones are better but still not good, if any water gets onto the relay from say the rear washer pipe detaching when frozen then you will have big current draw problems, I prefer to leave the relay unpowered.

 

On the MK2 I removed the fuse, on my Yeti (connected to the rear power socket)  can do that and also flip a switch, both are just accessible in the rear recess.

Thanks for the advice about removing it when not in use. Currently the only trailer I use is a small one with just road lights which are powered as I have mentioned up thread. The other internal caravan stuff I won't need powered up unless I actually have a caravan so I will keep unplugged most of the time. I assume that it would need to be plugged in for the MOT?

39 minutes ago, pikpilot said:

 

Although two cables can be put in parallel, they should be both be connected to the same double rated fuse.

 

So, yes, you need a 30A piggyback to match the fuse position you are using and secondly you need to use a fuse position that is rated for the current.

Don't forget that your chosen position in the fusebox will see the sum of your load current plus the current in the other fuse at that location so you can only use a piggyback if you will not exceed the limits of the upstream fuse. So ok if you use say, the cigar lighter fuse as that is intermittent use.

 

You can understand now why it is normal to run a 30 A cable from the tow bar socket directly to a dedicated fuse in the engine bay fuse box if you intent to supply a caravan which has high electrical loading.

 

 

I assume the cigarette lighter is powered when the ignition is off? Else I can't use that. I have found the large piggyback fuse tap you mentioned and have ordered it.

I assume I need a 30amp fuse at that end and a 20 amp at the other end where the load would be? Or would the fuse at the fuse box be ok for cable and load? I can do it either way as I will now have the parts.

Take a look for the westafella towbar fitting instructions, pretty sure it tells you exactly which fuses to use 👍

4 hours ago, langers2k said:

Take a look for the westafella towbar fitting instructions, pretty sure it tells you exactly which fuses to use 👍

Well I'm using this: http://www.towbarsdirect.co.uk/images/TEC3M.pdf

 

And of course this: http://www.towbarsdirect.co.uk/images/M7-WK7.pdf

 

Both on seperate power sources.

 

The TEC3M says 30amp

And the TEB7SA says 15amp

 

My question is If I use 1 30amp fuse at the fuse box for the TEC3M which protects the cable do I need another fuse next to the TEC3M of 30 amp for it or is the one fuse now sufficient?

 

I feel like I'm finally close to winning with this thing!

Edited 3 February, 20215 yr by lotrjw

A single 30a fuse at the fuseboard will protect both the cable and TEC3M.

 

Same deal for the TEB7SA, it just needs one 15a fuse at the fuseboard.

 

This assumes the cable used is suitable for 30a or 15a 

2 hours ago, langers2k said:

A single 30a fuse at the fuseboard will protect both the cable and TEC3M.

 

Same deal for the TEB7SA, it just needs one 15a fuse at the fuseboard.

 

This assumes the cable used is suitable for 30a or 15a 

The TEB7SA is connected via a separate power source I found in the boot, it's not sharing the one from the TEC3M. 

The cable for the TEC3M is definitely capable of 30amp I made sure of that.

Likely the power cable for the TEB7SA is fine for 15amp its a reasonable thickness.

You can use one 30A fuse if the sub load cables are rated at 30A too.

Another cause of wiring fires is when a small load is connected to a cable with a large rating and fuse but the sub load has only small cables. One example is where the 30A supply of the cigar lighter has a plugged in load which has a small cable with no fuse. This is the reason why you should always use a plug with a fuse in the tip (typically a glass fuse of 1A or less) to supply things like cameras and external navigation units such as Tom-tom (or use a lower current fuse in the cable).

The cable and internals of such low current devices will burn before they will blow a 30A automotive fuse.

As I said before, fuses are there to protect the wiring. You cannot then extend the cable with smaller wire without adding a fuse to protect that smaller wire.

That includes the hidden small cables and circuits in electronic equipment. However, the manufacturer will usually have a board mounted fuse on small loads such as a radio to avoid burning the printed circuit boards. These are to protect the unit itself. You still have to protect the cable as shorts through cut and chaffed insulation will cause melting of the cable unless it has an appropriate fuse in circuit.

11 minutes ago, pikpilot said:

You can use one 30A fuse if the sub load cables are rated at 30A too.

Another cause of wiring fires is when a small load is connected to a cable with a large rating and fuse but the sub load has only small cables. One example is where the 30A supply of the cigar lighter has a plugged in load which has a small cable with no fuse. This is the reason why you should always use a plug with a fuse in the tip (typically a glass fuse of 1A or less) to supply things like cameras and external navigation units such as Tom-tom (or use a lower current fuse in the cable).

The cable and internals of such low current devices will burn before they will blow a 30A automotive fuse.

As I said before, fuses are there to protect the wiring. You cannot then extend the cable with smaller wire without adding a fuse to protect that smaller wire.

That includes the hidden small cables and circuits in electronic equipment. However, the manufacturer will usually have a board mounted fuse on small loads such as a radio to avoid burning the printed circuit boards. These are to protect the unit itself. You still have to protect the cable as shorts through cut and chaffed insulation will cause melting of the cable unless it has an appropriate fuse in circuit.

Well I assume that the TEC3M unit is set up to handle that as they say fit a 30 amp fuse? the cables going from that unit to the 13 pin socket are quite thick too.

So I got the large piggyback fuse thing and found a spare slot on a bus bar that is perminantly live. I think its the bus bar with the cigarette lighter. Using a spare slot meant I didn't have to muck around with another fuse, but the piggyback thing meant I didn't have to put the cable into the back of the fuse box. Made the job much easier. 

I have disconnected it again because of battery drain though.

 

Oh and as for the other bypass unit, the second one I got, I think it's faulty, as I tried it on an older simpler car that doesn't have shared tail light wiring. The tails still didn't work. Never mind I have still saved money over having a tow bar company do the job.

 

I have even fitted a reverse light on my trailer. See picture. So a productive day.

 

Oh and thanks for the help from everyone that did.

Another update I have redone the power cables, I now have the wiring for the lights going to the fuse box too.

The lights now work with the ignition off, which means the trailer indicators flash when locking and unlocking the doors. Nice thing is I can unplug the both when I don't have a trailer on the back.

On 06/02/2021 at 22:21, lotrjw said:

 

 

.

 

Oh and thanks for the help from everyone that did.

 

I had a similair trailer to this and ditched all the rear lights in favour of much bigger/visible units as those rear lamps arent that visible at the best of times.  Cheap easy and effective, if your interested I'll post some pics.