Technical Rear light problem

[Riviera181]

Hi All,
I have a problem with the O/S rear light unit on my 2004 Ducato Motorhome.
With the side lamps on the O/S indicator remains on, when the indicator is switched on the side lamp and brake lamp flashes.
A bad earth maybe?
On the back of the light cluster all the bulbs earth via a black wire, but it would appear the black wire has a live feed to it, maybe the problem?


I am trying to find where the black wire runs to. It travels underneath the O/S of the camper bodywork in a plastic conduit and enters the chassis near the rear spring hanger.
Anyone know where it exits the chassis/or where it finally ends up?
Does it join other earth wires at a common earth point?
TIA

 

[digger58]

Check the connector block to the rear light unit.

 

[corcai]

Fiat didnt make that wiring. HiEvery motorhome manufacturer is different its not fiat from there is often a junction box at the front near where the motorhome body joins the cab

 

[Riviera181]

Fiat didnt make that wiring. HiEvery motorhome manufacturer is different its not fiat from there is often a junction box at the front near where the motorhome body joins the cab

Would the body builder/motorhome manufacturer go to the trouble of routing the wiring into and internally through the box section of the chassis?
Do you know where Fiat out the earth points near the front ?
Thanks

 

[digger58]

Fiat didnt make that wiring. HiEvery motorhome manufacturer is different its not fiat from there is often a junction box at the front near where the motorhome body joins the cab

And they certainly enjoyed using domestic cable and such like with no wiring diagrams! Took 3 hrs last year to trace a fault in the feed to my fridge from the alternator, found 3 identical red wires running back from the front of the cab, eventually found an in line fuse on the feed wire that was hidden behind the Ducato fuse box.

 

[lm04]

Save yourself some headache and digging and get/borrow a meter. Continuity test a section from the loom, to the bulb, then to the connector etc and see where the signal breaks. It will save chasing cables.

 

[Riviera181]

And they certainly enjoyed using domestic cable and such like with no wiring diagrams! Took 3 hrs last year to trace a fault in the feed to my fridge from the alternator, found 3 identical red wires running back from the front of the cab, eventually found an in line fuse on the feed wire that was hidden behind the Ducato fuse box.

I could understand if the body conversion items, such as the fridge etc had there own wiring set up (with no diagrams), but I would imagine that most Fiat campers start life as a chassis cab before the body is fitted. Therefore the logic (if there is any at Fiat) would be that all the "Fiat" fittings/O.E equipment such as the rear lights would carry their wiring configuration

 

[Riviera181]

Save yourself some headache and digging and get/borrow a meter. Continuity test a section from the loom, to the bulb, then to the connector etc and see where the signal breaks. It will save chasing cables.

Continuity testing the loom would be the way forward, but that is where the problem starts :
a) The black wire which connects onto the earthing bar in the rear lamp cluster seems to have a live feed running down it.
b) I need to know where the earth point/where the other end of the black wire ends to be able to continuity test. Plus I need to know definitely the route of the wiring to be able to check the various connectors along the way.

 

[digger58]

Most campers have a chassis extension, I know my rear lights are a strange set up, on drivers side(LHD) there is a junction box for the rear lights BUT the reversing light is not there, it comes down the right side of chassis!

 

[lm04]

Continuity testing the loom would be the way forward, but that is where the problem starts :
a) The black wire which connects onto the earthing bar in the rear lamp cluster seems to have a live feed running down it.
b) I need to know where the earth point/where the other end of the black wire ends to be able to continuity test. Plus I need to know definitely the route of the wiring to be able to check the various connectors along the way.

Ignore colours - red is not the only live colour! Black is a live in many european countries. If you are a german conversion you will almost certainly be black as live.

You don't need to know where the wire goes to test it - you bare a piece and go from there, to the cluster as I said before and it will tell you if there is an issue from the bared point to the bulb. Will save alot of head scratching!

The chances of the central loom being faulty is slim as the cable unless damaged is never put under stress. It will be joins either end. So you first take a bared piece of wire and continuity test from that point to the end point of the bulb holder. If it is fine - you have no fault there. Then do the same the other end.

If you are unsure where is what on the light end, just follow from bulb to wire joint. You don't need to know the other end as you can find the wire/trace from fusebox. As no fuses have blown. there is no short - it is an earth issue.

If you are live Black, then earth will been usually brown.