Full beam not working on oneside

Mat.123 · Nov 10, 2018

Hi all
I was driving home last night and noticed that full beam stopped working on the drivers side

.so I changed the bulb but with no success.

I noticed that Full beam worked when you flash (when you pull the stalk back to you) but nothing when you have full beam on properly.

Any suggestions before I dig in to the electrics

Mathew

bankz5152 · Nov 10, 2018

Switch likely burnt out. Had almost the same issue a couple months ago.

Kwakerman · Nov 10, 2018

Mat.123 said:
Hi all
I was driving home last night and noticed that full beam stopped working on the drivers side .so I changed the bulb but with no success.
I noticed that Full beam worked when you flash (when you pull the stalk back to you) but nothing when you have full beam on properly.

Any suggestions before I dig in to the electrics
Mathew

What model / year? Does it have dim-dip?

Jimsky Korsokov · Nov 10, 2018

I've had exactly this - measure the voltage going to the bulb, you'll probably find a strange value quite a bit lower than 12V and when you put a load on it drops lower - so low the bulb won't ignite. Trace your wiring through and find a poor connection - mine was at the fuse box, lots of blue fluffy corrosion that sapped the voltage on demand. May be at the switch also as previously suggested. I remade the bad contact and hey-presto, all the weird symptoms stopped happening and I stayed on the original bulb.

Mat.123 · Nov 10, 2018

Kwakerman said:
What model / year? Does it have dim-dip?

It's a 300tdi 1998

Mat.123 · Nov 10, 2018

Jimsky Korsokov said:
I've had exactly this - measure the voltage going to the bulb, you'll probably find a strange value quite a bit lower than 12V and when you put a load on it drops lower - so low the bulb won't ignite. Trace your wiring through and find a poor connection - mine was at the fuse box, lots of blue fluffy corrosion that sapped the voltage on demand. May be at the switch also as previously suggested. I remade the bad contact and hey-presto, all the weird symptoms stopped happening and I stayed on the original bulb.

Cheers for the advise, I'll have a look tomorrow and see what I can find . Much appreciate the help and resposens.
Mathew

nobber · Nov 11, 2018

I've never had a switch "burn out", I've had a few lose contact, easy fix, remove the plate, bend the contact up, clean and reassemble. Those switches are more than beefy enough to handle the lights.

jamesmartin · Nov 11, 2018

new switch, and even new lucas switches are a gamble, if it works on flash mode but not otherwise

dieseldog69 · Nov 11, 2018

I would check the H4 bulb connector first and work your way back, if it is the switch then fit a new one and it is very worth the effort to fit relays into the lighting circuit, there is a kit sold that is pretty much plug an play but if you like to tinker then it's even more satisfying to build your own loom.

I have 4 relays on my lights, each dipped and full beam has it's own relay and I also fitted some fuse and relay boxes under the bonnet to make a tidy installation of it.

neilly · Nov 11, 2018

dieseldog69 said:
I would check the H4 bulb connector first and work your way back,

Mat.123 said:
I noticed that Full beam worked when you flash (when you pull the stalk back to you) but nothing when you have full beam on properly.

If it works on flash mode then does that not mean it is OK at the connector?

Cheers

dieseldog69 · Nov 11, 2018

neilly said:
If it works on flash mode then does that not mean it is OK at the connector?

Cheers

No, there are 3 individual terminals in the H4 connector and it's usually the dipped beam terminal that corrodes, gets hot and melts the plastic terminal connector and presents the failure, the earth and full beam are usually perfectly fine.

I've had a few melt on me over the years, even with a blob of vaseline on fitting.

neilly · Nov 11, 2018

dieseldog69 said:
No, there are 3 individual terminals in the H4 connector and it's usually the dipped beam terminal that corrodes, gets hot and melts the plastic terminal connector and presents the failure, the earth and full beam are usually perfectly fine.

I've had a few melt on me over the years, even with a blob of vaseline on fitting.

OK, I thought it was the high beam side of the lights that lit up when you flashed your lights not the dipped beam side. The OP states it is full beam that has failed, but not on flash.

Cheers

dieseldog69 · Nov 11, 2018

neilly said:
OK, I thought it was the high beam side of the lights that lit up when you flashed your lights not the dipped beam side.

Cheers

When you flash it is supposed to be both elements that light up.

nobber · Nov 11, 2018

Have you checked the fuse? I've just had a bad fuse on one Hi beam and it still worked on flash.

Mat.123 · Nov 11, 2018

nobber said:
Have you checked the fuse? I've just had a bad fuse on one Hi beam and it still worked on flash.

Yeah that was this first thing I checked . Been a bit mental in work today so hopefully I'll update you guys on my findings.

Thanks all again

Mat.123 · Nov 11, 2018

dieseldog69 said:
I would check the H4 bulb connector first and work your way back, if it is the switch then fit a new one and it is very worth the effort to fit relays into the lighting circuit, there is a kit sold that is pretty much plug an play but if you like to tinker then it's even more satisfying to build your own loom.

I have 4 relays on my lights, each dipped and full beam has it's own relay and I also fitted some fuse and relay boxes under the bonnet to make a tidy installation of it.

View attachment 162547

I like the idea of putting relays into all lighting systems. I've just put relays on the spot lights so it may be worth doing the whole system

dieseldog69 · Nov 11, 2018

Mat.123 said:
I like the idea of putting relays into all lighting systems. I've just put relays on the spot lights so it may be worth doing the whole system

You certainly won't be disappointed with the resulting improvement in light output.

Mat.123 · Nov 19, 2018

Evening all
Just a quick update on my findings .
Checked all the obvious things like fuses and loose wiring to the headlight with no success.
So it was time to have a bit more of a look .

Unplugged all the wires to the right-hand headlight and side light etc and dragged back through the wing . Noticed that the spot light wiring was getting tight as I pulled it a certain point .

Only to discover that the previous owner had scotch locked the spots on to the main beam wiring and they had corroded

, so first job was to get rid of those s**t scotch locks and put fresh new wiring in with relays. And hey presto I have a full set of lights , no issues now (touch wood)

Thanks for all the advice guys , been much appreciated.
All the best

nobber · Nov 21, 2018

You dont still have the spots wired into the full beam do you?

dag019 · Nov 21, 2018

nobber said:
You dont still have the spots wired into the full beam do you?

Why would you do anything else? Surely that is where they are most useful!

Edit: or am I miss understanding and you are referring to directly wire in rather than through a relay?

Full beam not working on oneside

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