auto lecktrical stuff

[revjames]

I am setting about fitting a towbar to the newly aquired 07 Cmax. On the previous one I had, I was told I had to fit a multi relay to avoid excess current being drawn from the rear light circuits due to the trailerboard.

However I have heard that it will still work OK. Any thoughts? will 2 extra brake lights or an extra indicator (21W each) really make any difference? will it blow up the ECU?

Also anyone got colour codes for the rear wiring loom of aforementioned motor?

 

[Andy™]

modern vehicles may give problems. if you have a lamp failure warning on your dash, you will have that lit. also, some monitor load, so extra lamps and itll 'trip'. if your lucky, there may already by a towing connection there. otherwise, best to install a bypass box, along with feed to it from battery

also, its a legal requirement there is a device to warn of indicator problems. on bypass boxes etc, this is done by a buzzer which sounds whilst indicating. or on stuff with tow connections built in, if there is any indicator failure, the indicator light on dash flashes quicker than normal. why they think its more important that indicator work than brake or side i have no idea....

also, not got wiring info for that vehicle, but its usually easy to work it out. also if your lucky, all wiring will come from one side to light cluster, and other side, so you can pick up all connections from the same side. otherwise you need an idicator & side light feed from one side, and all other (brake, side, fog & ind) from the other side. earth onto chassis somewhere

and for towbars... the mechanical side is often easier than the wiring....

 

[Sidewinder]

Rev,

I'll put the word out.

 

[revjames]

Thanks sidey,

There seem to be people on the focus forums that have fitted towbar wiring without the relay and havent had a problem. What I need is the diagram/ wiring colours for the rear loom. There isnt even a haynes book for this car otherwise I'd buy one.

 

[spinlondon]

It depends on how your lights are wired.

Some have one thick supply to the light cluster, with thin wires to each bulb(they're called bulbs not lamps in the automotive world) for a proccessor to switch.

You brake, and the proccessor sends a signal telling the breaklights to work.

If all the bulbs have the same size wires then you should be fine, although you may have to change the indicator relay, as the added load may make the indicators flash too fast.

 

[revjames]

Thanks spin

I know (from the old Cmax) that the wires are all the same size (approx 1.5mm) I thought extra load would make them flash slower. If you blow an indicator bulb the remaining one flashes quicker doesnt it?

 

[spinlondon]

Yes that's right, why did I say faster?

---------- AUTO MERGE Post added at 23:51 ---------- Previous post was at 23:45 ----------

Oh yes, on Motorbikes it's the other way around.

There's a bi-metalic strip in the relay which when closed allows the current to flow to the indicators. Untill it heats up and opens breaking contact. The greater the load, the faster it heats up.

 

[Andy™]

Thanks spinI know (from the old Cmax) that the wires are all the same size (approx 1.5mm) I thought extra load would make them flash slower. If you blow an indicator bulb the remaining one flashes quicker doesnt it?

just take the lights out, see what colour wire goes to where, and scotch lock/other into the feed

 

[a1]

There is a chap on another forum that queried this on a new C0Max car in 2007. Of all the dealers that he went to, only one mentioned the relay. He was told that:

the electrics on the new C-Max have been upgraded, and installing a the electrics of a towbar by splicing into the existing electrics may put a spike the in ECU and cost loads/invalidate the warrenty!

Someone else replied that they were picking their car up that Friday and it was being fitted with a relay shortly afterward.

The new bumpers (07) are a lot deeper apparently. You don't want to have the wrong one and chop lumps out of your bumper, Rev.

Quote from that c-max website...

The towbar fitter used a bypass relay setup to provide the power for the trailer and caravan wiring so no extra load is drawn through the normal circuits when towing. I think the supply for the 12v 10A socket in the boot was used. Mobile fitter charged

 

[revjames]

just put the bar on. You would think a maker like Ford would be consistent with fixtures and fittings. I had to take the screws out of the arch liners first - Torx - no probs got a set. Then there was a 10mm nut in each wheel arch, awkward place so set of ratchet ringspanners comes out. Then behind the rear reflectors, an 8mm head self tapper - so out with the 1/4 drive set. Finally underneath is a pair of philips, plastic screws which refuse to budge so hammer and chisel comes out. I remember the days when a simple socket set alone would take the whole car apart! what a faff but still did it in an hr.

Havent done the electrics yet. Will take Andy's suggestion of popping the clusters out and manually looking for the cable colours. Admin, thanks for the suggestions above. I am going to try it by tapping directly in to the loom.