18 replies to this topic

[dgear1984]

I am trying to find some led bulbs to replace the 12v 2.2 987 screw in bulbs I have in my mk1 smiths clocks.

 

Every company I have contacted have said they are for negative earth only, my car is positive earth and i do not wish to change it.

 

Anyone know of someone who sells positive earth bulbs? Google search returned nothing. Someone must sell some

 

Thanks Dave

[black olive]

I would buy one and try it. im sure they have built in diodes so they can be connected either way round

[A-Cell]

I am trying to find some led bulbs to replace the 12v 2.2 987 screw in bulbs I have in my mk1 smiths clocks.
 
Every company I have contacted have said they are for negative earth only, my car is positive earth and i do not wish to change it.
 
Anyone know of someone who sells positive earth bulbs? Google search returned nothing. Someone must sell some
 
Thanks Dave

May I enquire as to why? You won't be saving much current and LEDs will be more expensive than bulbs.

[sledgehammer]

I wonder if you could just wire your own LED (with resistor) 

 

the opposite way around from normal ?

Edited by sledgehammer, 29 August 2013 - 10:31 PM.

[tiger99]

black olive,

 

Please do not give advice that you are not competent to give. What actually happens, unless the lamp has a bridge rectifier, not a simple diode, is that the 12V will exceed the reverse breakdown voltage of the LED and probably destroy it, if there is no diode. If there is a single diode, the LED simply will not light, ever, on reverse voltage.

 

If the lamp has a bridge rectifier (unlikely for a car part) it will be specified as suitable for AC or DC.

[Dan]

  And it wouldn't be listed as negative earth!

 

  I don't imagine anyone makes positive earth in-car LEDs as there are no positive earth cars being made and there haven't been for decades.

[KernowCooper]

Have a word with Paul here http://www.norbsa02....m/goffyleds.htm

He keeps + and - earth leds for the Motorbike resto guys which all the old ones were + earth

[Dan]

That surprises me, they are there though.  987 is really called an MES E10 (miniature Edison screw 10mm) and they are on that list.

 

  Just to note that if you have an alternator on this car you can't use a plain LED as the warning lamp for it, you will have to include some more components to make the alternator work.  Also you need to check the LEDs are bi-directional if the gauge has the single central indicator repeater and you want to use one there.

[RemKingston]

If you are unable to source positive earth LEDS then another alternative would be to isolate wiring to negative earth LEDs running a direct earth back to the battery.

I wouldn't recommend it and if you sold the car then the new owner is going to be left with a load of additional wiring and a puzzled look.

 

Best practice would be to convert the vehicle to negative earthing in my opinion.

 

Guide:
http://www.minimania...trical_polarity

 

As with any electrics, if in doubt, call an expert :)

[jaydee]

I take it you want to upgrade the illumination, cant see otherwise why you want led for warning lights. Also i'm pretty sure the ignition light wont work with a led bulb.

I dont know if as a work around for led illumination bulbs this gonna work.. : use a new bulb holder, the insulated type, the connect the -ve of the holder to the +ve off the original wiring, and the +ve from the holder to the negative from the wiring.

[KernowCooper]

To be honest unless its a 100% period for year restoration your better off converting to - earth, I knew Paul had then as the classic bike boys use them. Your right jaydee on the ignition light wont work on a normal led and nor will the single indicator warning light.

Edited by KernowCooper, 30 August 2013 - 11:14 AM.

[dgear1984]

Thank you for the link, I have contacted Goffy.

 

I do not wish to change to negative earth nor run extra wiring, but thanks for the suggestions.

 

The car is very much period/factory spec, I realise LED's are not but it would be a simple thing to change back if i ever needed.

 

I was only intending doing the actual dash illumination lights as the dials seemed very dully light at night. I was not intending doing the ignition/warning lights as a. the system would not work and b. they are bright enough.

 

Thanks Dave

 

 

 

[tiger99]

I wonder why your dials seem so dim? I have noticed that myself on various cars which are getting fairly old and still on original bulbs, and sometimes the problem was that the filament had been evaporating and coating the inside of the glass, so much less light was getting out. They looked dull yellow, rather than white. New bulbs would fix that. Maybe also there is an accumulation of dirt on the dials, as they are not fully sealed?

 

I do appreciate your reasons for keeping the car original. However there are ways of converting to negative earth which do not spoil the appearance and are reversible, such as the alternators you can get now which are built into a dynamo casing and look original. The wiring should only need minor alteration, not too visible. But of course it is your car, to do with as you please.

[sledgehammer]

I think tigger has hit the nail on the head - old bulbs dim / soot

 

but also wondering if a higher wattage bulb would help (illumination only- & not stupidly over rated)

 

the wiring will be able to take a few watts more - as long as the speedo won't be affected by the heat

[mini670]

I replaced my dash bulbs with LED`s i have a -ve earth car.

Be sure to add a load resistor to the alternator light or it will not activate the charging circuit and the LED will stay on. I made this mistake so i have to take the dash out again. Im just going to put a normal incandesant bulb back in instead of messing about with resistors.