Have just fixed a towbar to my Croma. Phew what a pain. The biggest job is getting the bumper off and having to deal with all the corroded screws. Thanks to all forum members who helped with info on getting the bumper off, I would have been pulling my hair out without your help.

Any way the bar is now fitted and just have to wire it up. I have a Universal 7 way bypass relay kit and the first thing to do is to get a cable to the battery for the live feed.

Has anyone done this, if so, where did you push the cable through the bulkhead into the engine bay? I was considering connecting to the cigeratte lighter with an in line fuse instead of taking the cable to the battery. Has anyone done this or have any other ideas?

Dont take it off the fag lighter as you turn the car off the trailer lights no longer work.......

Has it got an internal fuse box... i'd take the feed from that you can get these (i assume the croma uses mini blade fuses

http://www.ebay.co.uk/itm/Add-Circu..._Technology&hash=item2a14b1c2ff#ht_1552wt_982

5 mins with a multimeter will find you a constant live circuit

pull the original fuse probe the fuse socket and work out which way round it is

you want it so the piggy back gets its supply FROM the constant live rail of the fuse box or you will find it keeps zapping the accessory fuse your scrounging off if you get it back to front

Best and only reliable and sensible solution is to run TWO 15Amp fused feeds directly from the battery +ve terminal. These feeds should be rated/capable of 25Amps to minimise voltage drop. This can be critical if you are planning to power a caravan and it's charging and power circuits.

You then run these leads down the engine compartment rear bulkhead and then into the protective plastic tunnel/channel where the brake/other pipes run to the back of the car. You then bring them back up into the rear up through the boot floor pan.

I have my bypass and auxilary power relays located on the rear nearside of the car.

Below are the wiring notes I made when I installed my Croma tow bar and wiring. NOTE! they are obviously specific and thus may not be relevant for you installation so please read with care.

Before attaching the blurb below you should note the following:

1) DO NOT attempt to connect your 7 way bypass relay wires near to the rear light clusters. Un-tape, un-wrap the loom to a position around the top of the rear wheel turrets before connecting. If you screw up then you have plenty of room/wire length to recover. Many people connect/Scotch Lock in a few inches behind the light unit. Big BAD mistake. The cable and connectors to the light units are the most valuable areas of the cable loom.

2) Allow excess cable length before terminating/connecting to the socket/sockets. Two reasons. 1) if you have to remake/repair damage/corroded cable end joints into the sockets the you need "clean and free" cable. 2) Many modern 13 Pin Connectors will swivell / roatate and fold down/up. This 90 degree rotation with 13 core cable requires decent cable length and flexibility to not strain or damage final output connector wiring. If you have room and cable length then an extra two or three feet of stowed cable is preferable. This another reason for going for 25Amp rated feed cable. Minimise all voltage drops.

So.... now for the blurb ..... posted "asis", no liability etc. etc. accepted. Any questions the please ask and do not assume.

Croma Tow bar and Wiring Information 05 Feb 2007
====================================

Tow Bar : Brink 4361 'CLick' Detachable
Bypass Relay : PCT ZR1328A (anti-chatter)
Combi Relay : PCT ZR1220
Audible Buzzer : PCT ZR1000A (not required & not fitted)

Wiring Info
===========

From Battery (twin core 25A per core)
============
Bat +ve -- Red --- 15A fuse ---> ZR1220 +12V Input
Ground -- Black ----------------> ZR1220 Earth

Bat +ve -- Black --- 15A fuse ---> ZR1328A Term.B +12 Input
Ground -- Red ----------------> ZR1328A Term.A Earth

ZR1328A Wiring
==============

Car To ZR1328A
--------------
Bat +ve -- Black --- 15A fuse ---> ZR1328A Term.B +12 Input
Ground -- Red ----------------> ZR1328A Term.A Earth

Reversing Lights -- Diego Grey/Red (N/S) (Clear tie wrap) --> ZR1328A White Wire
Fog Lights -- Diego Orange/Black (N/S) (Green tie wrap) --> ZR1328A Blue Wire
Brake Lights -- Diego Green (N/S) (Red tie wrap) --> ZR1328A Red Wire
RHS Side Lights -- Diego Black/Yellow (O/S) (Yellow tie wrap) --> ZR1328A Brown Wire
via Black Wire
LHS Side Lights -- Diego Yellow/Red (N/S) (Yellow tie wrap) --> ZR1328A Black Wire
RHS Indicator -- Diego Blue/Black (O/S) (Blue tie wrap) --> ZR1328A Green Wire
via Black Wire
LHS Indicator -- Diego Blue/Red (N/S) (Blue tie wrap) --> ZR1328A Yellow Wire

ZR1328A To 13 Pin Socket
------------------------
ZR1328A Term.a Reverse Lights -- 13 Pin Cable Red/Black --> 13 Pin Socket - Pin 8
ZR1328A Term.b Fog Lights -- 13 Pin Cable Blue --> 13 Pin Socket - Pin 2
ZR1328A Term.c Brake Lights -- 13 Pin Cable Red --> 13 Pin Socket - Pin 6
ZR1328A Term.d RH Tail Lights -- 13 Pin Cable Brown --> 13 Pin Socket - Pin 5
ZR1328A Term.e LH Tail Lights -- 13 Pin Cable Black --> 13 Pin Socket - Pin 7
ZR1328A Term.f RH Indicator -- 13 Pin Cable Green --> 13 Pin Socket - Pin 4
ZR1328A Term.g LH Indicator -- 13 Pin Cable Yellow --> 13 Pin Socket - Pin 1
Ground -------------------------- 13 Pin Cable White --> 13 Pin Socket - Pin 3

ZR1220 Wiring
=============

Car to ZR1220
-------------
Bat +ve -- Red --- 15A fuse ---> ZR1220 +12V Input
Ground -- Black ----------------> ZR1220 Earth

ZR1220 To 13 Pin Socket
-----------------------
Permanent Live Output ----------- 13 Pin Cable Clear --> 13 Pin Socket - Pin 9
Switched Output 1 ----------- 13 Pin Cable Purple --> 13 Pin Socket - Pin 10
Switched Output 2 not conneted

Ground (Pin 9 ret.) ----------- 13 Pin Cable Grey --> 13 Pin Socket - Pin 13
Ground (Pin 10 ret.) ----------- 13 Pin Cable Pink --> 13 Pin Socket - Pin 11
not connected ----------- 13 Pin Cable Cream --> 13 Pin Socket - Pin 12

13 Pin Socket / Cable Wiring (NOTE! Colours from Pins 8 to 13 non standard!)
============================ -------------
ACTUAL Common Usage
------ ------------
Pin 1 - Left Indicator Lights - Yellow (Yellow)
Pin 2 - Rear Fog Lights - Blue (Blue)
Pin 3 - Earth for Pins 1 to 8 - White (White)
Pin 4 - Right Indicator Lights - Green (Green)
Pin 5 - Right Tail Lights - Brown (Brown)
Pin 6 - Brake Lights - Red (Red)
Pin 7 - Left Tail Lights - Black (Back)
Pin 8 - Reversing Lights - Red/Black *(Pink
Pin 9 - +12V Permanent Supply - Clear *(Purple)
Pin 10 - +12V Switched Supply - Purle *(Grey)
Pin 11 - Earth Return for Pin 10 - Pink *(Clear)
Pin 12 - Sensing Device - Cream or Buff *(Buff)
Pin 13 - Earth Return for Pin 9 - Grey *(Black/Red)

S130 - thanks for your detailed description. Am I right in saying that if I locate the by-pass unit on the rear nearside of the car I have to take cables across from the rear off side brake and rear lights to the by-pass unit or do the brake and rear lights have a common feed.

you will need a 2 core cable (usually) to take the offside indicator and side live light feeds to the relay box

brake lights are on one circuit

oh and perhapse need another core for fog lamp (if its in the same cluster) depending how the wire runs

Thanks Andy Monty for that.

I have one last question on this towbar electrics saga.

If I manage to route a cable for the live feed from the back to the battery in the engine bay what size cable would be required as there would be a fair current flowing when the lights are on and brake lights etc at the same time?

I have a cable which was supplied with the by-pass unit but I think it may be a little thin for the job. Reckon the copper is less than 1mm in diameter.

Also I intend to fit an in-line cartridge type fuse at the battery end with an 8amp fuse. Any thoughts?

1mm cable is rated at 10 amps. I think you will need a bigger fuse than 8 amps though, as each bulb requires just under 2 amps to operate and you have to allow for all the lights being on together. I think 30A is the norm but I maybe wrong.

If my maths are correct this might come in handy

https://www.fiatforum.com/grande-pu...12-n-socket-7-way-bypass-relay.html?p=2126898

You need TWO 2.5mm square cross sectional area cables. One for the lights and one for auxiliary electrics (caravan charging, 12V fridge, etc.)

https://www.fiatforum.com/doblo/277837-towbar-electrics.html

Running any cable at its rated capacity is not advisable. 2.5mm square cable is rated at 20 amps. When fused at 15A then you have plenty of safety margin.

Whilst you can get away with lower capacity for the lights you will probably run into problems with the auxiliary power circuit.

The aux electrics should be powered via a voltage controlled power relay (e.g. ZR1220). This relay ensures that the caravan battery and fridge etc. are ONLY powered when the engine is running and the alternator/battery voltage are above a threshold which is measured at the relay and not the battery. If you do not use 25A rated cable then the voltage drop along the cable will be to high and the relay may not cut in, or may cycle in/out/in/out depeding on load and temperature.

Hope this explains why 25A or more rated cable is best used.

I had the local towbar fitter in Wigan fit mine, when i picked it up he said that he would NEVER touch another Croma unless the pwner paid double his normal charge, said it was the worst one he had ever fitted,

Not sure why this should be?

Croma is just a Vectra/Signum varient. Two power feeds from battery, bypass and aux power relay wiring. Mechanical towbar fitting is on of the easiest ones I've done.

What he complaining about having to remove the rear bumper? This is a quite common requirement these days.

Hi
I have got a Fiat Panda 1.1 active eco 2010, I have a tow bar on the car but no electrics, everybody I have contacted so far tell me the canbus wiring system makes it a very difficult and successful operation and suggest that a genuine Fiat Panda tow hitch which comes with their wiring kit is the only answer, pray tell me their is another way.
p.s. sorry about my spelling
Kind regards Dibnah