I have fitted a towbar to my 2003 Vectra 1.8 which was easy. The problems I have had have been wiring it.It seems be working ok on the driveway.But when I drive off and touch the brakes (not always the first time) the bulb failure light comes up on the dashboard. Sometimes it is the left brakelight and sometimes it is the right. If I turn the ignition off and then on again it seems to reset until I touch the brakes again.
Do I need a 7 way split relay or a smaller one as it only seems to be the brakes???
P.S I forgot to mention that the trailer is hitched at the time.
the vectra's as with many modern electronics in cars need a dedicated wiring loom,thats plugs into the cars wiring inside panel in the boot/tailgate are.
the circuits on the car are set up for installing a loom such as this,just one extra cable req. to connect to power dis. point on main circuit.
you will get this fault every time until you instal correct wiring system.
I fitted my tow bar and wiring to my last Vectra. You need the bypass relay and it will stop the problem of the warning system.
Because of the auto bulb fail change system on the Vectra you must take the feeds from the correct location. The Brake light feed must be taken from the high level brake light (the one in the tailgate). The high level brake light has no bulb fail change over function simply because there is not other lights that can take its place. The feed to this is from a small white plug with 5 black wires connected. This plug is found at the top part of the rear electronic module in the left hand side of the boot. If I can remember correctly is the 2nd Black wire down on the front row of wires in the plug which is the 5th connector down (first 3 connectors are not used) But a simple test lamp will find the correct wire.
Below is a copy of an email that I sent to one of my colleagues.
"Most of the Bypass relays have standard 7 pin wiring colour coding.
Green wire from Transistor relay/Relay Bypass box connects to Black with Grey trace (dirty white/grey)
Yellow wire from Transistor relay/Relay Bypass box connects to Black with White trace
Black wire from Transistor relay/Relay Bypass box connects Grey with Black Trace
Brown wire from Transistor relay/Relay Bypass box connects Grey with Red Trace
Red wire from Transistor relay/Relay Bypass box connects to Black wire that Supplies the High level Brake light. If you look at the fuse board in the boot, you will see 5 black wires coming from a white connector.
The fog lamp control is the Blue wire. I didn’t connect this so did not find the wire but if you need me to I will have a look
The reversing lights is the White wire (didn't connect)
Wire the socket to the screw connectors on the Transistor relay/Relay Bypass box as indicated on the label, except the earth from the socket connect this to the vehicle earth.
Connect the Transistor relay/Relay Bypass box earth terminal to the same location as the socket earth to eliminate any potential.
The power for the Transistor relay/Relay Bypass box is
simply plugged with a 15amp spade connector into the spare fuse connector. which is above the 40amp fuse. Use a test lamp to find the terminal that is carrying the 12v. A 15amp fuse must be installed on this wire between this connection and the Transistor relay/Relay Bypass box."
I also took some pics of the connections if you can't follow the above.
There are modules that have the electronics built in. The module simply plugs into the rear electronic pack on the Vectra. They cost about £50.
Either the relay Bypass module or the plug in module will stop the bulb warning system from malfunctioning. If you go into a Vauxhall dealer they will give you a load of rubbish about the car needs to be put on the diagnostics PC and set up to allow you to tow. This is the case if you want the warning system to also monitor the trailer bulbs. But if you are not worried about the trailer lights being monitored, you can save yourself a couple of hundred pounds by fitting a Bypass relay set.
We have mainly Vectras in our fleet (approx 250) and at least 100 of us have fitted Tow bars ourselves. We are an electronics design and diagnostics company, so we do have a little understanding of electrics and electronics. Believe me this is not a difficult task to perform.
In theory at least, you could make your own controller for the tail lights, using 6 transistors and relays. It is probably cheaper to buy a dedicated wiring kit though and a lot easier and neater. The dedicated kit should plug straight into the loom so no need for scotch locks or cutting into the cars loom.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.
Topic: Towbar wiring
