08 Focus, Dipped Headlamp Failed But Bulb and Fuse ok. Help!

Eddie182

Eddie182

Eddie182

Associate
Joined
11 Dec 2006
Posts
1,091
Location
Lincoln
As per the title, had the O/S dipped beam fail this morning and have just changed the bulb and checked the fuses, still nothing.

Has anyone got any ideas what the cause may be? :confused:
 
I'm thinking relay or switch as well, but can't find a diagram of the aux junction box that actually shows which relays are which. Although the Haynes manual I've just bought does number the relays, it doesn't actually list which number relay is for what function.

Anyone have any idea, or have any clues where to look? I'd obviously like to rule out the relay before I look at the switch, which is going to be more costly.
 
Eddie182 said:
Although the Haynes manual I've just bought does number the relays, it doesn't actually list which number relay is for what function.
Click to expand...

The Haynes should list them by the numbers that are on the inside of the engine fusebox lid, it does for my old mondeo in the back of the book?.

*Edit, R9 for dip beam to be exact (for manky mondeo)*
 
It lists (as part of the circuit diagrams) all but the numbers for the headlamp relays, and based on the diagram on the aux junction box the headlamp relays aren't there that I can see.

What has me stumped though, is that the circuit diagrams show only one relay for the dipped beam and one for the high beam. It's only the dipped beam that has a fault, and only on the o/s. The n/s dipped beam is fine so I'm starting to think the relay is not the problem.

I can't even see how the switch could be the cause, as if one side is operating normally the switch is obviously working.

I can only see 2 possible causes.

The first being that it was the bulb and, despite the chances of it happening are tiny, one of the replacement bulbs was faulty and it happened to be the one that went in the same side. I'll switch the bulbs around tomorrow to rule that out.

The second is that there is a wiring fault.

But I think that if swapping the bulbs tomorrow doesn't help, it's off to the garage.
 
Eddie182 said:
It lists (as part of the circuit diagrams) all but the numbers for the headlamp relays, and based on the diagram on the aux junction box the headlamp relays aren't there that I can see.

What has me stumped though, is that the circuit diagrams show only one relay for the dipped beam and one for the high beam. It's only the dipped beam that has a fault, and only on the o/s. The n/s dipped beam is fine so I'm starting to think the relay is not the problem.

I can't even see how the switch could be the cause, as if one side is operating normally the switch is obviously working.

I can only see 2 possible causes.

The first being that it was the bulb and, despite the chances of it happening are tiny, one of the replacement bulbs was faulty and it happened to be the one that went in the same side. I'll switch the bulbs around tomorrow to rule that out.

The second is that there is a wiring fault.

But I think that if swapping the bulbs tomorrow doesn't help, it's off to the garage.
Click to expand...

Not sure how common it is, but I remember working with a few cars where the left and right lamp circuits are seperate, sometimes tied in with the opposite site rear lamp - hence one "side" can have a failed relay?
 
Na, there's usually only one dip relay & the output for the front dipped beam is split in two (both fused) after the relay output. It won't be the switch because that's only one output, which is already triggering the relay to operate the other light.

It's either the bulb, fuse or wiring on the o/s. I expect the earth is just behind the headlamp & is easy to check. A cheap multimeter to check for voltage at the bulb holder would be a good purchase!

Does swapping the good bulb over to the o/s work?
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom