14 replies to this topic

[System]

Guys I have found an odd electrical "fault" I have done my own fix but concerned I maybe hiding the fault.

 

Basically I have LED SMD type tail and brake bulbs. If I brake my radio, cluster and headlight switch all light up!

 

My initial thought is a bad earth but so far I can't seem to find one. Because of this I put it down to the LED bulb being faulty and causing an issue. I decided to establish which bulb was faulty by removing one or the other until the issue went away. So I removed the drivers side and the fault went! fantastic. However if I refitted it and removed the passenger side the fault also went :/ not so easy!. I decided to replace the bulbs with some new ones to be on the safe side but again the fault re-appears.

 

However

 

If I fit the standard filament bulbs I have no fault at all I can mix and match between LED and Filament on passenger and driver and have no issue at all. My fault only happens if I have both LED's in together.

 

I have decided to just stick to filament bulbs as they don't cause and issue and I'm not fussed over if its LED or not but want to put my mind at rest that having fitted the filament bulbs I'm not hiding a wiring fault that could give me headaches later on.

 

I'm thinking its a resistance thing but a friend of mine still thinks its an earth loop back.

 

Any input and help is greatly appreciated!

[Carlos W]

So if you brake it's like the side lights are on?

[slidehammer]

I would think it a resistance issue, as quite often the flasher unit doesn't like the LED bulbs as they don't draw enough load through the flasher unit and don't function properly. The other thing to bear in mind is LED will only let current flow one way direction as they are diodes, this might be having an effect.

[System]

@ Carlos yes its like the sidelights are being switched on though they don't come on when I brake.

 

@ slidehammer I thought resistance too, my flasher units are resisted but I would not expect the brakes to need it as its a simple on/off switch?

 

So if you brake it's like the side lights are on?

 

Yes just like that but from what I can see the sidelights don't come on (I maybe wrong)

 

 

I would think it a resistance issue, as quite often the flasher unit doesn't like the LED bulbs as they don't draw enough load through the flasher unit and don't function properly. The other thing to bear in mind is LED will only let current flow one way direction as they are diodes, this might be having an effect.

 

My flashers are resisted. however I would not expect the brake lights to need it as the circuit for the brake lights is a simple on/off system

[Carlos W]

They could be faulty LED units.

They may be providing power to the sidelight pin

[hhhh]

If your ground is bad in your taillights, the current will flow through the LED with very little resistance and on through the parking light circuit instead of to ground where it should go. This would explain your problem. Try temporarily doubling the grounds at your taillights one at a time (and front park lights) to find the problem.

Edited by hhhh, 27 March 2017 - 03:52 PM.

[System]

They could be faulty LED units.
They may be providing power to the sidelight pin

I've tried new units same problem


  

If your ground is bad in your taillights, the current will flow through the LED with very little resistance and on through the parking light circuit instead of to ground where it should go. This would explain your problem. Try temporarily doubling the grounds at your taillights one at a time (and front park lights) to find the problem.

I'll give it a go!

[hhhh]

It occurred to me that my scenario is impossible if the brake lights and tail lights are both LED with single polarity since they would be opposing each other polarity wise. It's possible that they manufacture them dual polarity now though since LEDs on a chip are so cheap they may as well put a pair in there back to back with reversed polarity so they work with positive or negative Earth, but not sure.

[KernowCooper]

The trouble is there are very poorly made leds out of china and they are causing all sorts of problems, stick with standard bulbs in my advice if they are working ok, and your sure you have a good earth to the lamps

[hhhh]

I bought a headlight LED H4 unit from China and it fell to pieces in under an hour on my BSA. I was able to collect the remains out of my headlight shell and make a custom LED taillight out of it though. Their idea of headlight dipping was inserting a resistor in series with the LEDs to make them really dim.

[tiger99]

An automotive grade LED "should" have at least a diode added, to protect it from reverse polarity, because the LED itself will often be destroyed if full battery voltage is applied in the reverse direction. Better wuality ones have a bridge rectifier so they work equally well both ways round.

But it is not LED problems that are the root cause of your symptoms. You appear to have sneak circuits caused by broken earths, possibly more than one. Faulty LEDS alone can not mysteriously energise one circuit from another.

But I advise against fitting non-standard LEDS instead of bulbs. There are legal issues which may get you into trouble. However I am glad that others are waking up to the menace of Chinese junk. If we don't buy it, it will eventually go away.

[tiger99]

Oh, hhhh, I particularly suggest not messing about with headlights. Those you definitely can not legally convert to LED at the moment, and failure is liable to be catastrophic.

[hhhh]

Here in BC, Canada, LED headlights are legal if they are designated "HL" on the lens, but you can't legally swap in an LED bulb into a non-HL designated lens. 

[tiger99]

That is as it should be, but UK law as yet makes no provision for LED or HID updates, which are only allowed if type approved with the car.

It seems that Canada is more sensible. The UK may catch up eventually. Our problem is that the Department for Transport, which used to be the Department of Transport, and it's underlings including the Driver and Vehicle Standards Agency, recently renamed from the Vehicle and Operator Services Agency, are stuffed with incompetent idiots with their own agendas, some of which are pure nonsense.

But I have grave doubts about the ability of anyone to make a direct H4 replacement. The power density in the LEDS would give poor reliability. Really, the entire light unit needs to be redesigned to do a proper job. Not that it prevents the Chinese from trying....

[hhhh]

The ones I had were pathetic. Seven little PCBs held together by solder on the edges which was an incredibly fragile construction.