How do I fix a faulty full beam tell tale please?

I think the best place to start is with the bulb, if that's okay, check the condition and tracks of the printed circuit board on the instrument cluster, is there a feed to the bulb ?

If no feed, then it'll need to be traced back through the loom.

Have you checked to see if there is any water ingress to the ECU in the passenger foot well ?

Are the earths situated under the headlights good and grounded ?

You could try disconnecting the headlights to see if the warning light illuminates.

I have lent my Workshop manual/wiring diagram to a friend of mine at the moment, I'll try and get it back off him.

OK. Worked it out.


My best guess is that because of the way your replacement front lights work there isn't any leakage back through the dipped beam filaments. Can't remember exactly how it all worked but there is a relay in there that I think operates the dipped beam. What I do remember is that there was a small bulb in the back of one of the clusters that shone nowhere and we couldn't really work out what it was for. I now suspect that this is to provide an alternative leakage path for the telltale.

So first thing to check is whether the telltale works when headlights are on and switched to main beam. It may be that the MOT tester has only checked whether it works by pulling the flash to pass. It's not designed to work then, only when headlights on and switched to main beam.

If that fails then check that pesky little seemingly pointless bulb on the back of the cluster. If that hasn't blown and is properly connected then check the telltale bulb in the instrument panel.

I'll wait with bated breath for updates.

Have fun.

Hi gang, here's a quick update.
I tried the telltale on full beam and it doesn't illuminate.
I inspected the bulb in the loom and it appears to be intact with all of the elements whole. However, it is chromed so not easy to see clearly.
I lost the light before I could strip the instrument cluster down so will try to get to that on Tuesday when I'm free next. I'll take a peek at the telltale bulb then. It might also give me an opportunity to tackle the replacement stalks.
Cheers,
Guy

Paul, you're a blommin' wizard and no mistake guv'nor.😁

I used an H4 bulb as per your suggestion and the tell tale illuminates. So, there's an issue with the wiring on the new lights.

What's the next step please?

Edit*. I don't know if it's pertinent but the sidelights in the cluster aren't wired in. The sidelights on TOG are taken directly from the OE loom. I don't think it affects anything but thought I'd mention it, just in case.

Thanks Paul. A multimeter is on my shopping list so as soon as I pick one up I'll do as you suggest.
Again, very grateful for your help.
All the best,
Guy