Anyone know how Ford Headlamp levellers work?

[AMC Rebel]

I mean I know the mechanical and basic electrical idea of these, but I was wondering - since the switch has 4 positions, how does the motor unit in the lamp "know" which position to go to and how it does it "know" when it gets there?

 

Neither of the adjusters is working on the Mondeo (they both do on the Puma, but I feel it would be unfair to raid it for parts )

 

It's not a huge issue of course, but I am nothing if not Mr Curious. I dismantled the headlight unit, and the motor, there's a circuit board in there with a little IC and some diodes and resistors.  Applying current to the motor had it turning until one of the components went pop and that acrid smoke that is actually the blood inside electrical stuff indicated I had done something stupid.

 

 Nothing ventured nothing gained and it isn't any worse as it didn't work anyway.

 

There are three connections to the motor unit - one is earth, but are the others up and down?

 

Surely it can't be that simple - in order for that to work the swtich would have to send "up" or "down" - and it would have to have some mechanism to "know" which way it was being turned.

[tooSavvy]

left field guess....

 

Possibly similar to a fuel gauge sender rheostat >> you ask for F / half / Empty with the dash knob and the circuitry seeks a happy equilibrium with the sliding voltage.

 

Kinndaa

 

 

TS

[scaryoldcortina]

Servo motor controlled with PWM...

[sierraman]

You'll find on older Fords they rarely work. On the top of the headlamp there's a hex with a flat screwdriver slot. I think you adjust them that way.

[AMC Rebel]

Servo motor controlled with PWM...

 

I know what PWM is (just) from Vectra rear lights and Rover 75 trickery - but can you elaborate on how it works for these? 

[scaryoldcortina]

Yeah, the chip on the board near the motor is reading a clock signal (usually about 1.2MHz) from the level control (which also has a chip). The postion of the control potentiometer changes the length of the signal pulse and the motor uses this to determine position using another potentiometer connected to the output drive.

 

I think. I've had a few beers and didn't check any of that!

[Pillock]

S'about it, yeah. Well done on the old drunken explanation

 

Pulse width modulation. Changes the ratio of on to off (the width of the pulse) which is a way of doing variable signals with a purely digital signal. Like servos on a radio controlled car.

[AMC Rebel]

Thanks - the PWM on Vectra lights is for dim/bright and has replaced the old twin filament stop/tail lights. I think it's used for dim/bright on LEDs too - hence the flicker on dashcam footage. So it sounds lkke the three connections are most likely pos and neg for the 12v motor, and a signal connection. From all this, I am suspecting the switch could be at fault (although I have buggered up one of the motor circuits now)

[AMC Rebel]

BTW Rover 75s have sep bulbs for tailight and stoplights but if canbus detects a dead tailight it uses PWM to illuminate stoplight at reduced intensity - clever eh - so clever it outwits owners at times - eg I have bulb out warning but all lights are showing.

[sierraman]

I'd get Dominic Littlewood called up then go round the shysters house that you bought it off and demand a refund whilst shouting at him as he tries to get in his car. 😀

[AMC Rebel]

I'd get Dominic Littlewood called up then go round the shysters house that you bought it off and demand a refund whilst shouting at him as he tries to get in his car.

Ha ha ha - I had meant to post in t'other thread - I am very pleased with the car - and after all, there wouldn't be any fun in it if everything was 100% fully working - also gives me an excuse to go to the scrapyard.

[mikebee]

Head light adjustment thing no good at all if you've got prolapsed front springs.you can end up lighting up the road about 6 feet in front of the car.no fun on a murky night on the A68.

[tooSavvy]

^^ same in the Savvy (springs ok!)....

 

Very short beam despite 'fully' up [ 0 ] on wheel

 

I parked facing a wall.. Wound wheel fully LOW then fully HIGH. Then 'jiggled' the thumbwheel at HIGH & like Lazarus himself the fferrs eased up a smidge

 

$hite chink $hite again... Ah well

 

 

TS