Technical Dipped Headlights stuck on

[suffolkmoose]

Hi Guys. Got a problem with my dip headlights stuck on, ducato 120 2008. Headlight relay seems ok, swapped with alternate and same problem. No other bulbs affected, so not Parking, or Follow Me related as far as I can see. It has occured very soon after a service, could a connection to the OBD port have caused this? Any thoughts appreciated.

 

[Communicator]

Hi Guys. Got a problem with my dip headlights stuck on, ducato 120 2008. Headlight relay seems ok, swapped with alternate and same problem. No other bulbs affected, so not Parking, or Follow Me related as far as I can see. It has occured very soon after a service, could a connection to the OBD port have caused this? Any thoughts appreciated.

You did say any thoughts. I am by no means an expert on the x250, but to try and start a discussion here are some possible areas.

1. Steering column stalk switch or connectors. On later models resistor coding is used between the switch and the BCM. Not sure when introduced.
2. BCM problem, hope not as replacement expensive.
3. Possible "rusty junction" problem below LH headlamp, but this does not seem very probable, as dip beam relay ia in cab.

 

[suffolkmoose]

Really appreciate the input, thanks. My thoughts so far...its not a relay problem, it tests Ok, and swap for alternate has same issue. There is no apparent visual issue in the BCM. The switch/connectors are next point of attention, but possible resistor coding is not something I had concidered so thanks for that. Hoping to get fault codes analysed today so will provide update asap.

 

[rayc]

The dipped beams, items F010 and F011 on the drawing are fed via relay T01. The relay is activated by an output from the Body Control Module which should only be present when the ignition is on and the light switch is On. I presume the lamps go off if the relay is removed? What voltage do you get on the individual fuses to each lamp?

 

[suffolkmoose]

Hi Rayc.
Many thanks for your interest and input. Yes, both lights go out when relay T01 removed. 12.35V at both fuses.

 

[rayc]

Hi Rayc.
Many thanks for your interest and input. Yes, both lights go out when relay T01 removed. 12.35V at both fuses.

Then assuming the relay is not stuck on it would seem the output from the BCM that switches the relay is permanently low 0v. On your model is the lamp switch 3 position off, sidelights , headlights or the later 2 position off, lights on ? Do the diped beams go off if the ignition is switched off?

 

[suffolkmoose]

Then assuming the relay is not stuck on it would seem the output from the BCM that switches the relay is permanently low 0v. On your model is the lamp switch 3 position off, sidelights , headlights or the later 2 position off, lights on ? Do the diped beams go off if the ignition is switched off?

Lamp switch is 3 position. No -dipped beams stay on all the time, even with key removed

 

[rayc]

Lamp switch is 3 position. No -dipped beams stay on all the time, even with key removed

I guess you need to confirm whether the 0v that is keping the relay energised (relay contact 86) is coming from the BCM or if there is a short to ground. Perhaps disconect the lighting stalk and see what happens to the lamps.

 

[suffolkmoose]

I guess you need to confirm whether the 0v that is keping the relay energised (relay contact 86) is coming from the BCM or if there is a short to ground. Perhaps disconect the lighting stalk and see what happens to the lamps?

I think thats the next step, after i get a fault code check on wednesday. Do you believe a ground short can come directly from the stalk, when there appears to be no other issues?

 

[rayc]

I think thats the next step, after i get a fault code check on wednesday. Do you believe a ground short can come directly from the stalk, when there appears to be no other issues?

The ground signal from the BCM to operate the relay is provided by the BCM. It is some time since I have had the 3 position switch but it provides an input to the BCM that provides a different resistor value for the side or headlights i.e. not a voltage or ground. As I said disconnect the switch at the connector in the steering wheel surround so that the switch is disconnected from the system

 

[suffolkmoose]

Thanks - will let you know how it goes. I assume if lights go out when switch is disconected the fault is in the switch or connector. If lights stay on the fault is at BCM end? Unless there is something between the. two?

 

[rayc]

Thanks - will let you know how it goes. I assume if lights go out when switch is disconected the fault is in the switch or connector.

That is the logic.

 

[suffolkmoose]

Todays update. Diagnostics reveal 7v is coming from the BCM holding the relay in. All signals from the stalks are ok. Nothing for it but order a new BCM and programming from Fiat. Many thanks for all the advice. I will confirm the problem has gone in a few weeks after BCM has been shipped and installed.