MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Automatic headlights

Dear All

I am currently undergoing a heritage body shell rebuild of my 72B, which is subject to the usual issues well documented here. I am taking the opportunity to add several updates to the electrical system, one of which is a system for automatically switching on the dipped beam in low ambient light levels. What I’m struggling with is where is the best place to locate a photo-electric cell that will sense the light level?

Does anyone know where these sensors are located on modern cars that have this feature?

Any clues welcome.

Many thanks
Richard
Richard Thompson

Theyre usually in the part of the rear view mirror thats adhered to the windscreen, in the same place as rain sensors, facing outwards of course. Maybe you could find a scrapped car with that type of mirror and fit that to the car?
Ross Kelly

Richard,

The location varies from vehicle to vehicle.

On my car built by GM it is on the dash just inside the windscreen and is part of the remote locking sensor.

Physically it is a small plastic rectangle which covers the out lights on , remote locking / unlocking and rain sensing wiper activation if the latter two are fitted.

It is subject to dust blocking the signal and anything on the dash covering it but otherwise it works well.

Pete.
Peter Thomas

Ross, Peter,

Thanks for your comments.

I'm currently building the electronics so I'll tryout some locations on the dash before I drill holes in the new shinny shell.

Cheers

Richard
Richard Thompson

Richard I am really interested in this modification. Can you tell me more about how you plan to do it?
regards
mark
Mark Mathiesen

Hi Mark,

Apologies for the delay in responding – business trips !

The way I plan to do this is quite simple and I am using commercially available items. At the core is a simple Vellman light sensitive switch kit. (MK125)
See:
http://www.maplin.co.uk/SEODynamicPages/modulealias.asp?ModNo=28574&alias=Light%20Sensitive%20dusk%20to%20dawn%20Switch

and

http://www.velleman.be/downloads/0/manual_mk125.pdf

This basically activates a relay on the PCB when the light level drops below a preset level. I plan to use this on-PCB relay to power a slave relay (12v /30A Lucas item). This relay will take power from the brown circuit and send power to the side and dip beam circuits. The electronics will be housed in a die-cast aluminum box with suitable connectors. Power to the electronics will be from the green circuit through a on of switch. This switch ( Auto on / Auto Off) will be placed some where on the console as a push button.

On the PCB is the photo-electric cell will be wired out to a yet to be decided location, hence the question. I probably will encase the photocell in araldite epoxy glue and mount in a rubber grommet to fit the body wherever I end up placing it. I think some experimentation will be needed. In addition I think the Vellman electronic circuit may need to be modified so that the lights stay on for, say 20 seconds, after the light levels rise. I have not addressed this yet; again I think I’ll need to experiment.

Hope this helps.
Richard Thompson

This thread was discussed between 06/04/2008 and 13/04/2008

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now