Towbar Wiring

[davidfowler2000]

Anyone got any experience with fitting a towbar to a Ovlov 740 estate? Personally I don't have any quibbles about getting the old socket and spanner set out to put the bar and ball on but how about the wiring? How easy is that? I can follow a wiring diagram but I'm always afraid of cutting and splicing wires - especially on a car - as I'm always afraid I might do something unintentional and let all the smoke out of the wiring loom. I'd also quite like a twin output for charging leisure batteries off the car while towing. Not that I have any towable equipment (yet), I just want the old barge to have it's image completed.

[Richard]

You have to be careful with the wiring or the extra load fries the bulb warning system. 940s have a plug intended for pre-wired towbar electrics, if your car has one you can cut the plug off and connect directly to the wires. Alternatively you can use a 7 way bypass relay.

[dieselnutjob]

The S type socket for charging can pull a lot of current so be careful.

They use a different heavier cable than the lights.

Also the standard changed and different caravans or wiring standards place different loads.

for example:-

Pin 4 is permanent live. On old caravans this only supplied the lighting circuit but on new caravans it charges the battery; in this case the switching of the charge circuit is done by a relay inside the caravan instead of the car.

Pin 2 is switched live. Old caravans charge the battery from this whereas new caravans sometimes use this to trigger charging from pin 4, or sometimes they use the fridge circuit to trigger it.

Pin 6 is switched live fridge feed.

Pins 3 and 7 should both connect to chassis.

I normally run two 20 cables from the battery to the S socket. One cable goes to pin 4 and through a relay to pin 2. The relay can be triggered from something like the wiper motor permanent feed.

The other cable goes through a relay to pin 6.

I fuse both cables with 20A fuses.

[Richard]

If it has the pre-wired plug that's all catered for too. I'd give you more detail but I'm posting from the phone. A search of the VOC forum might help or I'll give a fuller answer when I get home.