Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) the Ultimate LED Headlight?

They look great Peter 👍🏻

Love the could too, my first ever brand new car in 1975 a Leyland Mini S was that colour

Hi Peter. You got me thinking. AFAIK, the Can system looks at the resistance of your light bulb but it has to do that by looking at the current flow and assuming 12v. On the other hand your new LED needs a certain current and voltage and presumably has a built in adapter to give it what it needs from the 10 to 15 volts of a car system.

So I guess you are putting a resistance in parallel with the light fitting? If so you need the highest resistance you can use with out triggering the canbus since heat = V^2/R . If you are only looking at 12v resistors then you are right - lowest wattage. If you are looking at general ballast resistors then highest resistance.

Likely this is Granny and eggs, and that is assuming I am right. Whch often as not isnt the case.

Some manufacturers do run lamps front and rear - Volvo being one of them.
Never ceases to amaze me the number who drive on DRL only in the dark - and wonder why their car can't be seen from behind!

I think you are right. Yes, the ballast resistors are in parallel, so the "brain" sees resistance and so current flow. That works for the side light.
What I don't understand is why I had to put a 3w ballast across the main beam. Without it Main beam would work, dip didn't.
I can only assume that without some load on main beam the dip beam switching circuit wouldn't turn on. I'm pleased there is no ballast needed for dip beam as it is on all the time, the mains only occasionally, and for flashing.
But like you I'm guessing, to be honest with electronics I'm out of my depth.

As it's the lower resistance of the circuit it'll draw more current, therefore it needs to be of significant power rating or it would burn out.

It's a shame we are forced to use such a clumsy method to avoid ECU/BCU error messages. From an electrical efficiency point of view the shunt resistor to emulate the higher current draw of OE filament bulbs makes a mockery of LED current draw efficiency. Fitting resistors also impacts on reliability of the electrics given extra connections and the need for adequate power handling of same.

I assume modern vehicles equipped with LED headlamps from new have either no ECU/BCU monitoring given their greater longevity, or its geared to the substantially lower current draw. Either way I wonder if there is a market for ECU/BCU tweaks to accomodate after market LED replacements without having to resort to messing with resistors.

I agree Richard ;this is the point I was trying to make earlier

James

Richard, I know MMC will do an ECU update, but the charge is an order of magnitude higher than the cost of a pair of shunt resistors. Yes, fitting the resistors is a pain: I soldered the wires but agree, that isn't for everyone.

Fortunately Peter MMC dialled out the BCU headlamp bulb monitoring on the 3.7 Roadster, assuming it would have been there for Mustang etc. So I had no hassles installing my LED conversion.

I guess the BMW monitoring you have was not tweaked similarly.

I did drop the headlamp fuse values though to reflect the lower current draw, each element (L/R, main/dip) being fused independantly.

UPDATE:

we went out on Friday evening for supper with the LogMog crew. A good pub and it was good to catch up.
I'm not a regular "noggin" participant, I prefer driving to talking, but this was a run across the New Forest.

It was a wet old night, but Tatka is waterproof... I got rather wet running from the car to the door!
Pn the return it was pitch dark and throwing it down.

The new headlamps showed what they are capable: the dip beam pattern is good, with a solid pool of light along the kerb and up into the verge.
Main beam is something else: brilliant white light, cats eyes glowing brightly as far as I could see.
Overall every bit as good as the LED lights on any modern car. I can see why MMC selected them for the Plus Six.

Expensive, yes. But possibly the vest upgrade I've made to the car.

There is a photo of the light unit in the first post on the thread.