Wiring to steering column dipswitch

[Steve6]

Hello everybody, Happy New Year,
I'm looking for some assistance in tracing why my headlights have stopped working on my 1948 P3 75 Six Light. Working as logically as I can I have checked voltage to the lighting switch (A) is present, which it is, the side lights work fine (S), and using a meter the output from the switch to the headlights supply (H) is fine. The headlight supply wire then disappears into the dash and the main loom, lord knows where, but I believe it must resurface at the dipswitch on the steering wheel, in order to select main / dip. But how does it get there? Does the supply pass through the bottom of the steering box and up the middle of steering column? If so, presumably the horn feed is routed this way too (works fine), along with the two return wires from the dipswitch to the main / dip beams. Presumably these then go to one of the round junction boxes on the inner wings?

If it looks like the dipswitch is at fault, how do you remove the central Bakelite boss safely? I have seen these for sale for £££s and don't want to crack or break it.

By the way, I don't think this is a bulb or fuse issue, unless you know better. I believe I have just lost continuity somewhere in what is probably the original loom.

Many thanks in advance for any help / suggestions you can give.
Best Regards
Steve

[47p2]

The dip switch is attached to the tube that goes the full length of the steering tube. You need to disconnect the clamp at the bottom of the steering box/tube, disconnect the wires to the tube and pull the complete assembly out from inside the car by starting in the front seat then moving into the rear seat and guiding through the back door aperture. It's tricky but not too difficult and you do need to apply a bit of pressure & bend the tube slightly to get it out. Make sure you don't over tighten the clamp when you refit or it will never come out again

[luli]

The horn/deep switch tends to get oxidized due to the high current passing through it. Using relays to carry that current is a great improvement to both the light intensity and switch life expectancy. See here how this is done: http://wp.me/pXLKy-1xp
You can also watch restoration of these switches here http://wp.me/pXLKy-136 and here http://wp.me/pXLKy-13p and here: http://wp.me/pXLKy-1Yn.
Since they are also used on Land Rover Series , they are very expensive.

[Steve6]

Wow, more complicated than I thought! Many thanks 47p2 and luli for your replies. I think for the moment I will check all other options first, and leave the dipswitch as the last resort. To be honest, I rarely use the car at night, but would like to get it through an MOT. I would be more inclined to bypass the steering wheel dipswitch with a completely different switch / relay rather than pull the whole column.
Thanks again
Regards
Steve

[Phil - Nottingham]

A foot operated type would be most convenient which although not period looks it and quaint as well. I prefer the foot switches anyway as on early LR's, P4's and P5's so there is plenty of choice

[lakesrally]

Book it in for a safety check, it does not need an MOT. If the dip is not working it will not matter if you are not taking it out in the dark.

[Steve6]

Hi Phil, I think I might just do that. A peek in the footwell shows just about enough room to fit a foot dipswitch, and I must say that, going by luli's pictures, the steering boss dipswitch looks somewhat under-engineered by Rover's usual standards, especially since it carries the current directly. This is probably a good time for me to convert to foot switch / relays on main and dip beam.

lakesrally - Thank for the reply. I hadn't realised that you could get a safety check, as opposed to a full test. Does it carry any validity? Mind you, I believe even a full MOT is only valid at the time of test. I spend most of my time driving to little village rallies within 30 miles or so, so sorting out my lights and getting an MOT is more like peace of mind for me, than an actual need.

Many thanks to both of you
Regards
Steve