Misbehaving LED projector bulbs

[Turboseven412]

Hi John,

Yes I think I need to properly investigate where the power loss is coming from, as I said I've cleaned all of the wire contact points/connectors which leads me to thinking its a switch that's at fault.  Good news, I was playing with the car this afternoon and I've now broken the dimmer switch!  So that's now to repair or replace, whether it was causing the issue shall never be known...

As for the electrical noise, I think that may have something to do with the flickering.  I've noticed that I can't put a multimeter anywhere near the engine whilst its running or it's goes haywire.

Prior to breaking the switch I'd cleaned the earth for the worst offending headlight, started the car and sure enough both lights remained on - beforehand starting the engine would cause the driver side light to go out.  But this doesn't really prove anything yet as they did both sometimes work... I'll have to get this switch sorted now before anything else.

Thanks for all the advice, I'll keep you all posted on the solution

[Tony Griffiths]

Which Seven do you have? A 'dimmer' switch? Might you mean dipper?

[David Cochrane]

To get round the problem of dirty 100-year-old-contacts in the switchpanel I fit a couple of relays, one to switch the headlamps on and the other to switch between main and dipped beam. BG971 here:  www.a7c.co.uk/spares.php#electrical

   

[Turboseven412]

Hi Tony, 

Yes I meant dipper switch sorry.  I have a '34 RP with the column mounted switch...before that were they all floor mounted switches?

David, whilst your here, I don't suppose you have any of these switches for sale?

I was thinking about fitting relays actually, use the sub-obtimal voltage to switch the relays on, which then powers the headlights directly from the battery.  Then a bit of power loss on that side doesn't really matter as much, so long as it can switch the relays on.

[Peter Naulls]

I had problems with LED stop and tail-lights years ago and I seem to remember the voltage drop was about 0.8v total. There was a tiny loss at every junction - fuse box, switch, bulb holder etc. all adding up to an "unacceptable" loss. The LED supplier confirmed that they had a tolerance of (from memory) 6V plus or minus 0.3V  Given the unsophisticated charging system on older cars I didn't think that was enough of a tolerance. The flashing trafficators had no hope as the voltage drop there was 1.5v with the solenoid activated, again the loss being the sum of several smallish drops.

I have a suspicion that more time and money spent on development would yield more tolerant and reliable LEDs.

[Turboseven412]

Hi Peter,

That is an awfully small tolerance, and probably explains why mine are cutting out at idle.  I'll have to check with the manufacturer of my bulbs and see what those are. 
The old halogens weren't bothered by low voltage...they just got dimmer.   It's a bit of a worry with these LED's that they both might just pack in at some point and leave me stranded, so I haven't really strayed far from the streetlights yet.  Although the halogens were so dim you couldn't leave the streetlights either....

Funny you should say that, I fitted the flashing trafficator LED's, and so far they are working brilliantly.  Haven't measured the voltage there but they seem to be holding up well (fingers crossed).

[tomcotez]

I had a similar problem with mine, they would work fine with engine off but not with the engine running. I also noticed that my automatic garage door control went haywire so concluded that the problem was RF interference!

I tried an HT lead suppressor which cured the door problem but not the lights. 

I then fitted a ferrite choke ring to the feed to each bulb, these filter out RF interference and give a clean supply. This has done the trick and they now work perfectly. Ideally they want to be as near to the bulb as possible - I put them inside the headlight bowls.

[Parazine]

To get round the problem of dirty 100-year-old-contacts in the switchpanel I fit a couple of relays, one to switch the headlamps on and the other to switch between main and dipped beam. BG971 here:  www.a7c.co.uk/spares.php#electrical

+1 for relays.

Some supposedly 6V LED's will cut out at 5.9V or lower so it pays to eliminate all the voltage drops in the circuit. Going around the circuit, measuring voltage drops across switches, wires and connection points can be very "illuminating"!