Does anyone understand indicator/flasher relay wiring?

Yes, I checked - the reason is that when the ignition is off, and the hazards are on, the "positive" connection to the dash indicator comes from the ignition circuit which is at zero volts. So the voltage is reversed -and the filament bulb would be flashing in step with the hazards with ignition off, and out of step with the ignition on.

With or without ignition on and hazards switch pulled out , the indicator bulb in the hazard flasher switch itself should be blinking away merrily. Unclip or unscrew the red lens from the switch pull knob and there is a bulb in there. ..

As for "perfection" It will be a squeeze but I think I can modify an LED bulb to fit a rectifier in it..


This is normal operation, current flows through the dash lights from the common connection at 12 volts to the output of the flasher relay.


When you pull out the hazards switch, the power for the flasher relay comes from the battery side of the ignition switch. The other loads on the ignition circuit pull down the voltage to zero volts. The voltage on the dash lamps is reversed.




In both of these, R is a sensing resistor in the flasher relay which tries to drive current when the contacts are open, to check for the presence of a load. This may also be responsible for LEDs glowing dimly depending on the model of the relay.
The relay from classiccarleds combined with an LED dash indicator bulb works OK.

 

Mike, which relay did you get from clasiccarleds? I think it might be worth me trying that. They have a bewildering level of choice in their website.

 

Going back to basics have you checked all your earths and given them a good clean

 

I just checked it was type CF14.

 

Yes. And the loom is only 8 years old because I had a new one fitted when the scooby conversion was done. The earths are fine.

 

The fact is that LED lamps are different in their voltage and current characteristics. The simplest LED lamps have clusters of many sets of 3 LED chips in series and a starting voltage between 8 and 10 volts , and will start glowing with maybe 0.001A of current, or less . In real darkness 0.0000001A of current produces a glow...
The current rises rapidly after 8 volts, but the typical power draw will only be maybe a few watts or so at 12 volts. This kind of LED will flicker like crazy as the battery voltage drops and increases.

These are typically made by low cost manufacturers in low cost locations.

They often use a simple low value resistor to control the current and I have some low cost LED festoon bulbs where the resistor melts the solder off the circuit board when the battery voltage is 14 volts. Thats because the voltage is dropped off the difference between the battery voltage and 8 volts across the LEDS. So at 12 volts the resistor has 4 volts across it, At 14 volts the resistor now has 6 volts across it and a power of 6/4 squared or 2.25 times at 12 volts. Meanwhile the current through the LEDs goes up by 6/4 or 1.5 times, hence a flickering.

If your earths are bad, the LEDS drawing less current will suffer less from voltage drops across bad connection, also often will not light up backwards like if the earths come off the rear light cluster and the indicators earth through the tail light bulbs and the headlamps instead.

More expensive LED lamps like the headlamps have boost converters in them , and internally may be working at 24 volts or more . so they can work on a 6 volt , 12 volt or 24 volt power system. These will tend to need more current to start lighting up as the boost converter uses some power, and may have a shutoff at low voltage in any case to stop blowing themselves up as the current draw increases as the voltage drops to keep the power constant. Another advantage of these LEDs is that they wont flicker with the battery voltage changing ..

These are made to a specification and cost more.

If you get a glow of light from an LED it means something is putting a voltage across it - and the most likely cause in the indicator circuit is the filament indicator bulb in the dash across the flasher relay - thats 1.2 watts or 2.4 watts with a later dual indicator light on the dash.

 

Just tossing around ideas here - this is only happening with the front indicators - the rear ones are fine. Firstly, is there anything I might have missed that might be putting a voltage through the front ones and not the rears? Or might it just be as simple as the voltage drop from front to rear has eliminated the problem?

So, therefore, (and I accept this might be very bad practice and somewhat overkill) would a possible solution be to relay the front indicators to eliminate the rogue voltage issue?

 

The front and rear indicator connections are parallel connected , so the differences will be either that you happen to have bulbs from two different batches with subtly different forward voltages, or that something else is feeding substantial current into the ground of the light clusters at the rear, reducing the voltage across the LEDs. It will not be a big difference, maybe only 0.5 volts.

Alternatively, you have a towing repeater relay at the back and this is changing the behaviour, also possibly injecting current into the indicator circuit to detect activity ..

The afterglow is actually a very small current so there wont be any real voltage drop between front and rear in the indicator wiring.

You could try the "canbus" trick and connect a 100 ohm 1 watt resistor to chassis from the indicator live at the front, see if the glow dims.