Vito Rear Fog Lights

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TheWayofPhil

New Member
Joined
Jul 26, 2021
Messages
2
Location
Glossop, UK
Car
Vito 111 '07 Diesel
Hi all, new to the forum

My front fog lights work okay, but on the rear there is no continuity or voltage to either unit. The other rear lights all work fine.

Is there a connector anywhere either under the vehicle or under the floor panels, or some other connector that may be at fault?

Regards, Phil
 
Only the o/s rear fog light will have a supply, it's to reduce confusion with brake lights.

A wiring fault, or even a lamp fault, will possibly disable the supply from the SAM. So after a few seconds if the SAM sees a fault there is no supply there to check for. It will reinstate and try again when you cycle the ignition.

The SAM could be faulty or even confused. It has been known for a battery disconnect to reset it. But you would be lucky there.

I would suggest 1st to try a known good lamp from the reverse.
 
The SAM could be faulty or even confused. It has been known for a battery disconnect to reset it. But you would be lucky there.

I would suggest 1st to try a known good lamp from the reverse.
Cheers mate;
I checked bulbs first, there is continuity through the bulb, but will try another

What's a SAM? - I'm used to old motorbikes and new to this lol
 
Under the bonnet,
above the n/s fr wing you have the fuse box (another smaller fuse unit is by the battery below the passenger seat).
In the main fuse box is the SAM which screws from below into the fuse board. Fuse board need to be removed to remove the SAM (not for the faint hearted).
In the box is also the ECU (and TCU is it's auto).

there can be lots of rain water around there and the drainage system can fail causing water onto the box.
The box has a good IP seal on the lid, but the lid and / or box can distort.
Water in there can be fatal to the electronics.

The SAM (Signal Acquisition Module) takes inputs from switches and more and translates that to an output to the end device.
Switch tells SAM to switch on fog light/s.. Sometimes there is fuse protection, often not.
If the SAM sees a fault it can often disable the output.

That should provide you with a simple understanding. The diagnosis can be far more involved.

If lamp replacement doesn't resolve it, next I would remove the light cluster (can be done in situ and disconnected) to apply 12 volts to the cluster pins to see if the lamp then lights.

Better to eliminate the obvious before diagnosing a faulty SAM, but that 'aint overly scary, just not a 2 minute replacement.
 

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