Dash light help please

[BRAD]

Hello everyone, changed all my dash bulbs for LEDs, every things fine apart from indicator dash lights don't come on at all now, indicators work fine as does everything else.
Any ideas?

 

[subheatadey]

I'm guessing it's to do with polarity, (I'm usually wrong ask Sparkywig ) I believe LED bulbs only work in one direction?

 

[samgopsill]

I concur, odd that you have just put the two indicator ones in the wrong way, could be something else, but start with turning the bulbs by 180 degrees and re fitting

 

[rlepecha]

I couldnt get the indicator ones to work, I bet your hazard switch doesnt work now either..
Also, hope you haven't changed the generator light, well, without putting a resistor inline anyway.

 

[BRAD]

Cheers, I'll have a go turning them around.
Your right the hazard doesn't work either, did the generator light? seems to work fine, why do I need a inline resistor? :?:

PS I hate electrickery :shock:

 

[rlepecha]

Cheers, I'll have a go turning them around.
Your right the hazard doesn't work either, did the generator light? seems to work fine, why do I need a inline resistor? :?:

PS I hate electrickery :shock:

The generator light might work, but it is questionable whether it excites the alternator enough and may sometimes cause charging issues. I can't remember if the resistor has to be inline or parallel with the bulb, someone else can probably confirm that.

I reverted back to the normal bulbs for the indicator ones because I couldn't get them to work, regardless of the polarity, one way I had working indicators(no dash lights) and non-working hazard switch, the other way the indicators didn't work but the hazards did. The LED dash lights seemed to cause the indicators to flash double quick(bit like having a bulb out).

I checked the wiring and it seems that with ignition on the base of the bulb holder is +12v and the wire is to ground controlled by the indicator switch, but with ignition off the base of the holder is always ground and 12v is switched on/off by the hazard switch+relay.
That's what I remember anyway...

 

[Dickie524]

I believe that the resistance of a standard bulb is integral to an indicator circuit working properly. Another car club of which I am a member has also found this - it is OK to replace all dash bulbs with LEDs except indicator ones.

The in-line resistor would artificially re-create the resistance of a 'standard' bulb hence the circuit would work again...

... so it is debatable if it's worth the bother :?:

It does mean that the bulb will never need replacing again - but how often does that happen anyway? And the current draw in amps will be the same...

 

[Peter Good]

I would add to that the generator bulb as well, if you are running an alternator.
There are a number of issues using an LED in place of the 12 volt bulb.
Firstly, as mentioned above, there may well be a problem getting the alternator to kick in, this is due to the lack of power coming via the LED to the alternator regulator.
Secondly, once started and the bulb or LED is extinguished, the D+ cable is used as a voltage sensing line by the regulator. If there is a large load such as headlights and wipers on, the voltage at the fuse-box will drop slightly compared to the voltage to the battery and the regulator compensates the output to match the load. With an LED in circuit this function is largely unable to operate.
Thirdly, and depending on the vehicles ignition system, many find the engine will keep running once the key-switch is turned off.
A Dynamo is not affected by any of the above!
Peter Good

 

[BRAD]

All fixed and working, cheers everyone.... next problem :lol:

 

[Dickie524]

How did you manage it - did you go back to normal bulbs or use a resistor? Or none of the above?!

 

[BRAD]

Kept LEDs in, swapped back to normal bulbs for the two indicator and generator lights.
Everything works now....... bar my brake lights, but that'l give me an excuse to put a new MC and disc conversion on.