Not good!!! 120 tow bar wiring

[Jack P]

Merry Christmas everyone, hope you're all having a nice relaxing boxing day. I was........

This burnt out this morning! It's part of the towbar wiring.

Drove about 10 miles this morning. Parked up, came back 15 minutes later to put something on the boot and was greeted with a nasty electrical burning smell and a bit of a fog! I thought it was the end After a bit of stiffing I found it was this little box in the back, which was kind of a relief. It's part of the Mr t tow bar wiring set. Nothing was plugged in to the tow bar socket BTW. Not sure what it does? Relay? The fuse going to the box had gone, but was still slightly touching. Is another one under the bonnet which is fine. Why would this have happened?? Need another one pretty quick for towing! Anyone now best place to get one? Mr T I suppose.

Going to put the car back together now to see if it still works.

 

[Chris]

Isn't that part of the wiring for the second socket - something to do with the fridge or battery charging rather than the indicators etc?

 

[Jack P]

Isn't that part of the wiring for the second socket - something to do with the fridge or battery charging rather than the indicators etc?

Mine is only a single socket.

 

[Jack P]

All the lights work fine apart from the indicators. I had to disconnect part of the towbar wiring and plug them back in directly. So at least I can drive it now. See attached for wiring of the towbar.

 

[flint]

Might be worth getting in touch with PF Jones for thoughts or a replacement: https://www.pfjones.co.uk

 

[Chris]

Perhaps it's a bypass relay. It doesn't look like one particularly. Older vehicles can just use a feed tapped into the relevant wire but I guess on a 120 with all that canbus stuff, it needs a bit of trickery.

 

[Jack P]

Might be worth getting in touch with PF Jones for thoughts or a replacement: https://www.pfjones.co.uk

Trouble is most places are closed till the new year. Why do these things always happen at the worst possible time!

 

[Jack P]

Perhaps it's a bypass relay. It doesn't look like one particularly. Older vehicles can just use a feed tapped into the relevant wire but I guess on a 120 with all that canbus stuff, it needs a bit of trickery.

I think it is some sort of relay.
I'm not sure the 120 is canbus? When I fitted it about 3 years ago I was going to just splice into the rear wires but thought it would be better and easier to buy the proper wiring harness. It's been fine up-to today.

 

[flint]

I think that it's a trailer flasher module/relay. Here's another place to try, but not sure if they'll be open tomorrow either. http://www.ecs-electronicsuk.co.uk

 

[Chris]

A quick google of the details on the housing suggest it's a split charge relay. Given how simple towbar wiring is, it's probably nothing very important. It might simply be a relay that boosts the indicators. You know what it's like on a trailer when you put your winkies on; everything goes dim. I have this on my wiring so that the signal from the original loom only triggers the relay which has its own power feed. That way you get nice bright trailer lights.

 

[Jack P]

Thanks for all the advice guys.

Phoned the local Toyota dealer (uckfield) this morning, most unhelpful. First he said it wasn't a genuine Toyota part! Well it most definitely is! Said I would have to buy a new wiring harness for 90 odd quid just for the relay. Thanks but no thanks.


Phoned the Brighton dealer. Who was most helpful. Took all the part numbers I had, said he would look into it and get back to me. Half hour later he phones to say he can get that part in tomorrow morning, 40 quid. Much more like it!

Just hope it doesn't do the same thing. Have checked all the wiring, which seems fine. The terminals on the connector are a little corroded, no way water could get in there. I think the thing has been heating up causing condensation. Hopefully it was just a one off dodgy part.

 

[Jack P]

All fixed and working now

They call the part a blinker detection unit.

Plus I found the cause; water. I pulled the trim apart to have a good look and found a very tiny bit of water. It had been coming in though the little rubber switch bit which turns the boot light on and off when opening/closing the door. Has been rather wet recently! Removed it and added a bit of sealant to the back. I've also relocated the little box just in case.

 

[Towpack]

I have something similar which is a split charge relay wired to the 7 pin S socket for caravan electrics/battery charging but if you don't have that socket it can't be that. The components look like one of those relays with a warning buzzer/bleeper to warn of a bulb out on the trailer.