Does anyone understand indicator/flasher relay wiring?

Fitted some LEDs to the front indicators and did a like-for-like swap of the indicator relay for its LED equivalent. Now the front indicators flash correctly when the hazard light switch is pulled, but when using the indicator stalk, the front indicators don't flash, as much as go dim-bright-dim-bright.

I'm still fiddling with the rear clusters so there are no indicators there at present.

I'm trying to understand the way that the relay and the indicators are wired up, so I can diagnose the problem. Can anyone please explain? I've tried reading the wiring diagram and I am still none the wiser.

 

As a first step, I’d get the rear LED bulbs in, see how it behaves. The relay’s driving a rather odd combination at the mo.

 

There's no combination - it's only driving the LEDs at the front. There's nothing in the rear. I removed the rear clusters completely. I'll be getting some led bulbs in the rear this weekend so I'll give it another go to see how it behaves then.

 

Try it with LEDs front and rear. That’s what it’s expecting as a load.

 

The problem is that there are three pins on the relay :
One is 12 volts in
One goes to the indicators
One goes to the dash light that flashes out of time with the indicators.

There is NO earth connection on the relay in the vw installation..

- the earth connection for the electronics in the relay has to go either to the LEDs when the LEDs are off, and to the green filament bulb on the dash when the LEDS are on .
Because the LEDs are so efficient, they turn on with just the current needed to run the relay's electronics.

The solution may well be to add a resistor (or a light bulb in a box .. ) to the indicator output wire on the relay and connect the other end to ground.

Or you (and I ) may have to swap the LED bulbs for the CANBUS ones that have built in resistors acrosss the LEDs to provide the load.


Just today, I have met exactly the same problem, but with an older electronic relay which wont flash at all.

The hazards work, because there is a big light bulb in parallel with the indicators in the switch, but the indicators dont.
And then when you turn on the ignition, without starting the engine the voltage drops a bit and the hazards stop flashing..

 

My initial attempt at a solution is to go back and order an LED compatible flasher from classiccarleds. It claims works from 0.01W to 120W ..

 

And part 2 of the solution I am going to try if the LEDs light up dimly is instead of a resistor to use an electronic load.

Basically when you indicate left, the first thing that happens (at least on my flasher relay) is that it needs to "see" 9.25 volts or more between the positive and the output terminal as it is connected to the bulbs.
With filament bulbs at this point they are basically a short circuit, there will be at least 12 volts so that triggers the flasher circuit to start pulsing. Every time the relay in the flasher opens, the voltage across the flasher hits 9.25 volts as the bulbs cool and so the timing circuit triggers again .

With the LEDs , they only start drawing current with (say) 6 volts across them. So the trigger voltage is never reached, unless the battery voltage happens to be over 15 volts .. 15 - 6 = 9 volts.
So my LEDs stay dim and the flasher wont start.

 

No change. The rear leds in the rear light cluster act as you would expect, and flash on-off-on-off. The front ones still seem to have some residual current going through them in the 'off' phase and so still flash bright-dim-bright-dim instead of on-off-on-off.

 

I already have an LED flasher relay installed. Doesn't solve the problem. In fact, out of curiosity I put the old relay back and it wouldn't flash at all.....

 

I am about to add another set of LEDs in the form of a side repeater (I thought this would be a good idea for when it comes to pulling out to overtake on motorways) - I'm going to use the US side marker lenses in the doors for this. I will have to see if this helps at all.

 

Might work, otherwise I’d suspect your relay. Flashing LEDs should be easier than flashing standard bulbs.

 

Overtake ha ha ha

 

I have a Subaru engine in my bus.

 

ha ha

 

On my setup with the wrong flasher relay they all come on dimly.


I expect what really happens is that the front indicator fittings have reflectors so they seem brighter than the Brazilian grey plastic boxes without reflectors often found fitted to buses these dayss.
If you actually look at the bulbs they are probably both glowing at the same intensity.

Your LED flasher relay is powering itself through the LEDs while the LEDs are meant to be off.

I trust that you still have a 1.2W filament bulb in the dash for the indicators, and your flasher unit is a type that does not need an earth connection, but uses the third terminal for the indicator bulb on the dash.

 

Not really, it’s only 4 bolts

 

I will check, but I’m pretty sure when I added LEDs to the dash a few years ago it was only the backlight bulbs I changed, and the indicator bulbs (according to the wiring diagrams there are 2) are still filament bulbs.

 

I have checked the "afterglow" of the LED flashers. And guess what - its the 1.2W (or 100mA at 12 volts) indicator lamp on the dash. If you change that for an LED bulb the right way round, the glow goes away.

Because the dash indicator lamp is across the relay of the flasher, it can provide enough current to make the LED corner indicator bulbs glow.


The dashboard LED lamp draws much less current than the filament lamp and this reflects in less current being available to make the LED indicator bulbs glow.

On mine with a filament bulb in the dash there was enough current provided to make the voltage on the LED indicators stay at 8 volts when they were meant to be off.

This also meant that the 1.2watt filament bulb only had a max of 4 volts across it.
Combined with it being blackened and ancient, it was basically glowing dim red through a green filter and completely invisible in sunlight.

With 2x21W filament corner indicator bulbs, the voltage across them at 100mA was basically nothing, so the dash indicator lamp would light fully.

With 2 indicator bulbs on the dash, thats a max of 200mA and that is getting quite close to the kind of current that the LED indicators themselves need to light up fully.

 

Thanks Mike, that worked a treat. Interesting polarity issues, but the front indicators are now behaving as they should. The LEDs in the dash are working one way around for hazards with ignition off and indicators with ignition on, or the other way for hazards with ignition on. I’m going to leave it as is, because the main thing was getting the indicators to work properly and they do.

 

Sadly I appear to have been wrong. The front indicators still have the dim-bright-dim-bright problem. Back to the drawing board.

I haven’t installed the side repeaters yet, so let’s see if that makes any difference.