Technical March 2006 Fiat Ducato (Motorhome) - Headlights not working

[boblett07]

Hello im looking for some advise/expert knowledge. As per the title, the headlights on my motorhome will not work. Bridging the secondary side of the replay in the engine bay fuse box turns the lights on.
Coming from the headlight switch, when turned off i get around 11.4v, when i turn the headlights on it drops to 0.02v. Same voltage readings going into the control unit/switch pack for fog lights/hazard light switch.
Coming out of the control unit, i get 12.28v with headlights turned off and the 12.04v when headlights turned on.
Ive ran my own wire from the control unit to the relay and makes no difference.
Any help would be appreciated.
Thanks
Rob

 

[Anthony489]

Hi

I assume your motorhome is based on the X244 model. If so, "Communicator" is your man so hopefully he will respond.

Are both the Dip and Main beam affected ?

The elearn schematics ( available online at http://4cardata.info/elearn/244/12/ ) show that the "Switch Control Panel" reference H090 is interposed in both dip and main circuits. Its outputs should drop from 12 V to a low voltage when required, in order to draw current through the dip and main beam relay coils and make them switch on.

I have no details of the internals of this unit, but its symbol implies some electronic content. Assuming that the headlamp relay coils are getting 12V on their supply (unswitched) ends, I suspect that the switch control panel is the root of your problems. Other owners have reported that a blown fuse for one of the several other circuits controlled by H090 (e.g. sidelights, interior lights) has a "knock-on" effect which can take out the headlights as well. I therefore recommend you systematically check for any lighting or similar items that are not working, and check for blown fuses especially F24 and F37.

 

[boblett07]

Hi

I assume your motorhome is based on the X244 model. If so, "Communicator" is your man so hopefully he will respond.

Are both the Dip and Main beam affected ?

The elearn schematics ( available online at http://4cardata.info/elearn/244/12/ ) show that the "Switch Control Panel" reference H090 is interposed in both dip and main circuits. Its outputs should drop from 12 V to a low voltage when required, in order to draw current through the dip and main beam relay coils and make them switch on.

I have no details of the internals of this unit, but its symbol implies some electronic content. Assuming that the headlamp relay coils are getting 12V on their supply (unswitched) ends, I suspect that the switch control panel is the root of your problems. Other owners have reported that a blown fuse for one of the several other circuits controlled by H090 (e.g. sidelights, interior lights) has a "knock-on" effect which can take out the headlights as well. I therefore recommend you systematically check for any lighting or similar items that are not working, and check for blown fuses especially F24 and F37.

Hi Anthony, thanks very much for the detailed reply.

From what i remeber its just the dip beam which aint working.

The 12v supply to the relay ignition side when the relay isnt fitted, i get around 12.4v. The earth side a little less around 11.7v.

I will double check fuses,carry out a fuction test of other lights and see if there is a common link/fault.

Would i find those fuses in the fuse box under the bonnet?

If everything seems ok, ill replace the switch control panel. Am i right in thinking, if i was to purchase a switch control panel with some black buttons/switches, the blanks are actually buttons and can be used?

Thanks again

Rob

 

[Communicator]

Hi,
Anthony, thanks for the recommendation. I have been otherwise engaged this afternoon, and hence I am trying to catch up.

However there is little that I can add, except to confirm that fuses F24, and F37 in the LH cab fusebox, B002 do control the headlamps via the "Switch Control Panel". I was not sure about F37, but having just carried out a test on my vehicle, I can report that removing F37 kills the main beam, as does F24 for the dipped beam. (I will repeat the test to itemise the effects more thoroughly.)

In the LH cab fusebox F24 is in the upper row and is at the right hand of three 5A (beige or tan) fuses. F37 is in the lower row and is at the RH end of three 10A (red) fuses

 

[boblett07]

Hi,
Anthony, thanks for the recommendation. I have been otherwise engaged this afternoon, and hence I am trying to catch up.

However there is little that I can add, except to confirm that fuses F24, and F37 in the LH cab fusebox, B002 do control the headlamps via the "Switch Control Panel". I was not sure about F37, but having just carried out a test on my vehicle, I can report that removing F37 kills the main beam, as does F24 for the dipped beam. (I will repeat the test to itemise the effects more thoroughly.)

In the LH cab fusebox F24 is in the upper row and is at the right hand of three 5A (beige or tan) fuses. F37 is in the lower row and is at the RH end of three 10A (red) fuses

Hi Communicator

Am i right in thinking the F24 fuse is for autos and F37 for manuals?

Ill double check the fuses again aint blown or missing!

Thanks

Rob

 

[Communicator]

Hi Rob,
Sorry incorrect. Unfortunately there are two fuses designated F24 on the x244. Fiat drawing error?
The F24 for auto transmission is in the engine bay fusebox. The F24 that affects the dipped beam is as described above.
I am currently, that is right now updating my personal diagram of the LH cab fusebox, and will post it when finished.

Can you please confirm whether you have lost main beam, dipped beam, or both?

 

[Communicator]

Hi,
Here are some drawings from my library. The table for the Switch Control Panel, and the layout of the LH Cab Fusebox are my own creations. Please be aware that there are some of my mods incorporated in the latter drawing.

 

[Anthony489]

Hi

Just to add to the above, for the Under-Dashboard Fuse/Relay/Junction unit:

F24 runs the Control Illumination, Side&Tail Lamps Dashboard Warning Light, Number Plate Lights and H090 via Pin D18
F37 runs the "PCC instrument panel" (also known variously as the Central Control Board, Switch Control Panel and H090) via Pin A2

Fiat documentation often has errors, and components seem to change name, presumably as different translators have worked on it without reference to each other !

As for having two F24's in the same vehicle, well that's pretty silly but it must have slipped through the net and then been too hard to correct.

One thing to be aware of. Fiat often used to run several items from one fuse, with at first sight no obvious commonality between them. I suspect that these items were cunningly chosen in such a way that if the fuse blew because of some obscure component failing, it would be immediately obvious to the driver because some other frequently used component (Like headlights) would also stop working.

 

[boblett07]

Hi Rob,
Sorry incorrect. Unfortunately there are two fuses designated F24 on the x244. Fiat drawing error?
The F24 for auto transmission is in the engine bay fusebox. The F24 that affects the dipped beam is as described above.
I am currently, that is right now updating my personal diagram of the LH cab fusebox, and will post it when finished.

Can you please confirm whether you have lost main beam, dipped beam, or both?

Hi

Thanks for the reply.

Ok i shall double check relevant fuses before purchasing a switch control panel.

Ive lost the headlights only. Mainbeam and sidelights work ok.

If i was to purchase a switch control panel, could i use one with blank buttons, from what i hear, the blanks pop off and there is an actual button underneath?

Thanks again.

Rob

 

[boblett07]

Hi

Just to add to the above, for the Under-Dashboard Fuse/Relay/Junction unit:

F24 runs the Control Illumination, Side&Tail Lamps Dashboard Warning Light, Number Plate Lights and H090 via Pin D18
F37 runs the "PCC instrument panel" (also known variously as the Central Control Board, Switch Control Panel and H090) via Pin A2

Fiat documentation often has errors, and components seem to change name, presumably as different translators have worked on it without reference to each other !

As for having two F24's in the same vehicle, well that's pretty silly but it must have slipped through the net and then been too hard to correct.

One thing to be aware of. Fiat often used to run several items from one fuse, with at first sight no obvious commonality between them. I suspect that these items were cunningly chosen in such a way that if the fuse blew because of some obscure component failing, it would be immediately obvious to the driver because some other frequently used component (Like headlights) would also stop working.

Hi

Perfect, much appreciate the info.

Ill give to fuses a good look over, test all companents and go from there. If all ok, ill order a switch control panel!

Thanks a lot

Rob

 

[Communicator]

Hi,
Results of testing on my x244.

Removing F37 kills direction indicators, which is the expected result, but it also kills Side & Tail lamps, Dipped & Main Beams.

Removing F24 kills the Dipped Beams.

I find that interesting.

As regards Anthony's comment about changes of name, I could be guilty of that, e.g. Brakelight or Stoplight, Switch Control Panel or Switch Control Unit.

 

[boblett07]

Hi,
Results of testing on my x244.

Removing F37 kills direction indicators, which is the expected result, but it also kills Side & Tail lamps, Dipped & Main Beams.

Removing F24 kills the Dipped Beams.

I find that interesting.

As regards Anthony's comment about changes of name, I could be guilty of that, e.g. Brakelight or Stoplight, Switch Control Panel or Switch Control Unit.

Hi

Yeh, strange why they would have 2 fuses affecting the same system.

Thanks for your help ill see how i get on with the fuses. Thankyou